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1
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Yang H, Gan Y, Jiang S, Zhu X, Xia Y, Gong D, Xie X, Gong Y, Zhang Y, Lei Q, Wang M, Li J. Genomic alterations in Bacteroides fragilis favor adaptation in colorectal cancer microenvironment. BMC Genomics 2025; 26:269. [PMID: 40102781 PMCID: PMC11921484 DOI: 10.1186/s12864-025-11421-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2024] [Accepted: 02/28/2025] [Indexed: 03/20/2025] Open
Abstract
BACKGROUND The occurrence and development of colorectal cancer (CRC) is an incredibly long process that involves continuous changes in the tumor microenvironment. These constant changes may ultimately result in genetic alterations and changes in the metabolic processes of some symbiotic bacteria as a way to adapt to the changing environment. Patients with CRC exhibit an altered abundance of Bacteroides fragilis (B. fragilis) as indicated by several studies. To better understand the genomic characteristics and virulence spectrum of B. fragilis strains in tumor tissues, B. fragilis strains were isolated from tumor and paracancerous tissues of CRC patients. METHODS The isolates were identified using 16 S rRNA sequencing, morphological analysis, physiological and biochemical characterization and PCR, and they were then subjected to whole genome sequencing (WGS) analysis. RESULTS A strain of B. fragilis enterotoxin (BFT) bft1-producing ZY0302 and a non-enterotoxin-producing B. fragilis ZY0804 were isolated from cancerous and paraneoplastic tissues, respectively. Analysis based on the core and nonessential genes showed that the genomic profiles of the isolates, ZY0302 and ZY0804, differed from those of B. fragilis from other tissue sources. This core and the co-evolution of non-essential genes may be the result of their adaptation to fluctuations in the tumor microenvironment and enhancing their survival. In addition, the ZY0302 and ZY0804 genomes underwent extensive horizontal gene transfer and varying degrees of genomic rearrangements, inversions, insertions, and deletion events, which may favor the enhancement of bacteria's ability to adapt to environmental changes. For instance, the virulence factors, such as the capsular biosynthesis gene clusters and components of the type IV secretion system, acquired through horizontal gene transfer, may facilitated B. fragilis in evading immune responses and managing oxidative stress. Moreover, our analysis revealed that multiple virulence factors identified in the isolates were mainly involved in bacterial adhesion and colonization, oxidative stress, iron acquisition, and immune evasion. This observation is worth noting given that enzymes such as neuraminidase, lipase, hemolysin, protease, and phosphatase, along with genes responsible for LPS biosynthesis, which are recognized for their association with the virulence of B. fragilis, were prevalent among the isolates. CONCLUSIONS In summary, it is our assertion that the alterations observed in both core and nonessential genes of B. fragilis, which have been isolated from tissues of colorectal cancer patients, along with significant instances of horizontal gene transfer to the genome, are likely intended to enhance adaptation to the evolving conditions of the tumor microenvironment. This study may provide new insights into the interaction between B. fragilis and the CRC microenvironment.
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Affiliation(s)
- Hao Yang
- Institute of Zoonosis, College of Public Health, Zunyi Medical University, Zunyi, Guizhou, China
| | - Yu Gan
- Institute of Zoonosis, College of Public Health, Zunyi Medical University, Zunyi, Guizhou, China
| | - Shenghai Jiang
- Institute of Zoonosis, College of Public Health, Zunyi Medical University, Zunyi, Guizhou, China
| | - Xianchang Zhu
- Institute of Zoonosis, College of Public Health, Zunyi Medical University, Zunyi, Guizhou, China
| | - Yang Xia
- Southwest Guizhou Vocational and Technical College, Xingyi, Guizhou, China
| | - Dengmei Gong
- Institute of Zoonosis, College of Public Health, Zunyi Medical University, Zunyi, Guizhou, China
| | - Xianrang Xie
- Institute of Zoonosis, College of Public Health, Zunyi Medical University, Zunyi, Guizhou, China
| | - Yao Gong
- Institute of Zoonosis, College of Public Health, Zunyi Medical University, Zunyi, Guizhou, China
| | - Yi Zhang
- Institute of Zoonosis, College of Public Health, Zunyi Medical University, Zunyi, Guizhou, China
- Key Laboratory of Maternal & Child Health and Exposure Science of Guizhou Higher Education Institutes, Zunyi, Guizhou, China
| | - Qian Lei
- Institute of Zoonosis, College of Public Health, Zunyi Medical University, Zunyi, Guizhou, China
| | - Maijian Wang
- Institute of Gastroenterology, Affiliate Hospital of Zunyi Medical University, Zunyi, Guizhou, China.
- , No. 149, Dalian Road,, Zunyi City, 563003, Guizhou Province, China.
| | - Jida Li
- Institute of Zoonosis, College of Public Health, Zunyi Medical University, Zunyi, Guizhou, China.
- Key Laboratory of Maternal & Child Health and Exposure Science of Guizhou Higher Education Institutes, Zunyi, Guizhou, China.
- , No. 6, Xuefu West Road, Xinpu New District, Zunyi City, 563000, Guizhou Province, China.
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2
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Lim B, Xu J, Wierzbicki IH, Gonzalez CG, Chen Z, Gonzalez DJ, Gao X, Goodman AL. A human gut bacterium antagonizes neighboring bacteria by altering their protein-folding ability. Cell Host Microbe 2025; 33:200-217.e24. [PMID: 39909037 PMCID: PMC11931560 DOI: 10.1016/j.chom.2025.01.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2024] [Revised: 01/06/2025] [Accepted: 01/14/2025] [Indexed: 02/07/2025]
Abstract
Antagonistic interactions play a key role in determining microbial community dynamics. Here, we report that one of the most widespread contact-dependent effectors in human gut microbiomes, Bte1, directly targets the PpiD-YfgM periplasmic chaperone complex in related microbes. Structural, biochemical, and genetic characterization of this interaction reveals that Bte1 reverses the activity of the chaperone complex, promoting substrate aggregation and toxicity. Using Bacteroides, we show that Bte1 is active in the mammalian gut, conferring a fitness advantage to expressing strains. Recipient cells targeted by Bte1 exhibit sensitivity to membrane-compromising conditions, and human gut microbes can use this effector to exploit pathogen-induced inflammation in the gut. Further, Bte1 allelic variation in gut metagenomes provides evidence for an arms race between Bte1-encoding and immunity-encoding strains in humans. Together, these studies demonstrate that human gut microbes alter the protein-folding capacity of neighboring cells and suggest strategies for manipulating community dynamics.
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Affiliation(s)
- Bentley Lim
- Department of Microbial Pathogenesis and Microbial Sciences Institute, Yale University School of Medicine, New Haven, CT 06536, USA
| | - Jinghua Xu
- State Key Laboratory of Microbial Technology, Shandong University, Qingdao 266237, China
| | - Igor H Wierzbicki
- Department of Pharmacology and the Skaggs School of Pharmacy and Pharmaceutical Sciences, Center of Microbiome Innovation, University of California, San Diego, La Jolla, San Diego, CA 92093, USA
| | - Carlos G Gonzalez
- Department of Pharmacology and the Skaggs School of Pharmacy and Pharmaceutical Sciences, Center of Microbiome Innovation, University of California, San Diego, La Jolla, San Diego, CA 92093, USA
| | - Zhe Chen
- State Key Laboratory of Microbial Technology, Shandong University, Qingdao 266237, China
| | - David J Gonzalez
- Department of Pharmacology and the Skaggs School of Pharmacy and Pharmaceutical Sciences, Center of Microbiome Innovation, University of California, San Diego, La Jolla, San Diego, CA 92093, USA
| | - Xiang Gao
- State Key Laboratory of Microbial Technology, Shandong University, Qingdao 266237, China
| | - Andrew L Goodman
- Department of Microbial Pathogenesis and Microbial Sciences Institute, Yale University School of Medicine, New Haven, CT 06536, USA.
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3
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Bayliss CD, Clark JL, van der Woude MW. 100+ years of phase variation: the premier bacterial bet-hedging phenomenon. MICROBIOLOGY (READING, ENGLAND) 2025; 171:001537. [PMID: 40014379 PMCID: PMC11868660 DOI: 10.1099/mic.0.001537] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/24/2024] [Accepted: 02/05/2025] [Indexed: 02/28/2025]
Abstract
Stochastic, reversible switches in the expression of Salmonella flagella variants were first described by Andrewes in 1922. Termed phase variation (PV), subsequent research found that this phenomenon was widespread among bacterial species and controlled expression of major determinants of bacterial-host interactions. Underlying mechanisms were not discovered until the 1970s/1980s but were found to encompass intrinsic aspects of DNA processes (i.e. DNA slippage and recombination) and DNA modifications (i.e. DNA methylation). Despite this long history, discoveries are ongoing with expansions of the phase-variable repertoire into new organisms and novel insights into the functions of known loci and switching mechanisms. Some of these discoveries are somewhat controversial as the term 'PV' is being applied without addressing key aspects of the phenomenon such as whether mutations or epigenetic changes are reversible and generated prior to selection. Another 'missing' aspect of PV research is the impact of these adaptive switches in real-world situations. This review provides a perspective on the historical timeline of the discovery of PV, the current state-of-the-art, controversial aspects of classifying phase-variable loci and possible 'missing' real-world effects of this phenomenon.
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Affiliation(s)
- Christopher D. Bayliss
- Department of Genetics, Genomics and Cancer Sciences, University of Leicester, Leicester, UK
| | - Jack L. Clark
- Department of Genetics, Genomics and Cancer Sciences, University of Leicester, Leicester, UK
| | - Marjan W. van der Woude
- Hull York Medical School and the York Biomedical Research Institute, University of York, York, UK
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4
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Chen B, Liu G, Chen Q, Wang H, Liu L, Tang K. Discovery of a novel marine Bacteroidetes with a rich repertoire of carbohydrate-active enzymes. Comput Struct Biotechnol J 2024; 23:406-416. [PMID: 38235362 PMCID: PMC10792170 DOI: 10.1016/j.csbj.2023.12.025] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2023] [Revised: 12/20/2023] [Accepted: 12/23/2023] [Indexed: 01/19/2024] Open
Abstract
Members of the phylum Bacteroidetes play a key role in the marine carbon cycle through their degradation of polysaccharides via carbohydrate-active enzymes (CAZymes) and polysaccharide utilization loci (PULs). The discovery of novel CAZymes and PULs is important for our understanding of the marine carbon cycle. In this study, we isolated and identified a potential new genus of the family Catalimonadaceae, in the phylum Bacteroidetes, from the southwest Indian Ocean. Strain TK19036, the type strain of the new genus, is predicted to encode CAZymes that are relatively abundant in marine Bacteroidetes genomes. Tunicatimonas pelagia NBRC 107804T, Porifericola rhodea NBRC 107748T and Catalinimonas niigatensis NBRC 109829T, which exhibit 16 S rRNA similarities exceeding 90% with strain TK19036, and belong to the same family, were selected as reference strains. These organisms possess a highly diverse repertoire of CAZymes and PULs, which may enable them to degrade a wide range of polysaccharides, especially pectin and alginate. In addition, some secretory CAZymes in strain TK19036 and its relatives were predicted to be transported by type IX secretion system (T9SS). Further, to the best of our knowledge, we propose the first reported "hybrid" PUL targeting alginates in T. pelagia NBRC 107804T. Our findings provide new insights into the polysaccharide degradation capacity of marine Bacteroidetes, and suggest that T9SS may play a more important role in this process than previously believed.
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Affiliation(s)
- Beihan Chen
- State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Science, Fujian Key Laboratory of Marine Carbon Sequestration, Xiamen University, Xiamen, China
- School of Oceanography, Shanghai Jiao Tong University, Shanghai, China
| | - Guohua Liu
- State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Science, Fujian Key Laboratory of Marine Carbon Sequestration, Xiamen University, Xiamen, China
| | - Quanrui Chen
- State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Science, Fujian Key Laboratory of Marine Carbon Sequestration, Xiamen University, Xiamen, China
| | - Huanyu Wang
- State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Science, Fujian Key Laboratory of Marine Carbon Sequestration, Xiamen University, Xiamen, China
| | - Le Liu
- State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Science, Fujian Key Laboratory of Marine Carbon Sequestration, Xiamen University, Xiamen, China
| | - Kai Tang
- State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Science, Fujian Key Laboratory of Marine Carbon Sequestration, Xiamen University, Xiamen, China
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5
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English J, Newberry F, Hoyles L, Patrick S, Stewart L. Genomic analyses of Bacteroides fragilis: subdivisions I and II represent distinct species. J Med Microbiol 2023; 72. [PMID: 37910167 DOI: 10.1099/jmm.0.001768] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2023] Open
Abstract
Introduction. Bacteroides fragilis is a Gram-negative anaerobe that is a member of the human gastrointestinal microbiota and is frequently found as an extra-intestinal opportunistic pathogen. B. fragilis comprises two distinct groups - divisions I and II - characterized by the presence/absence of genes [cepA and ccrA (cfiA), respectively] that confer resistance to β-lactam antibiotics by either serine or metallo-β-lactamase production. No large-scale analyses of publicly available B. fragilis sequence data have been undertaken, and the resistome of the species remains poorly defined.Hypothesis/Gap Statement. Reclassification of divisions I and II B. fragilis as two distinct species has been proposed but additional evidence is required.Aims. To investigate the genomic diversity of GenBank B. fragilis genomes and establish the prevalence of division I and II strains among publicly available B. fragilis genomes, and to generate further evidence to demonstrate that B. fragilis division I and II strains represent distinct genomospecies.Methodology. High-quality (n=377) genomes listed as B. fragilis in GenBank were included in pangenome and functional analyses. Genome data were also subject to resistome profiling using The Comprehensive Antibiotic Resistance Database.Results. Average nucleotide identity and phylogenetic analyses showed B. fragilis divisions I and II represent distinct species: B. fragilis sensu stricto (n=275 genomes) and B. fragilis A (n=102 genomes; Genome Taxonomy Database designation), respectively. Exploration of the pangenome of B. fragilis sensu stricto and B. fragilis A revealed separation of the two species at the core and accessory gene levels.Conclusion. The findings indicate that B. fragilis A, previously referred to as division II B. fragilis, is an individual species and distinct from B. fragilis sensu stricto. The B. fragilis pangenome analysis supported previous genomic, phylogenetic and resistome screening analyses collectively reinforcing that divisions I and II are two separate species. In addition, it was confirmed that differences in the accessory genes of B. fragilis divisions I and II are primarily associated with carbohydrate metabolism and suggest that differences other than antimicrobial resistance could also be used to distinguish between these two species.
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Affiliation(s)
- Jamie English
- Institute for Global Food Security, School of Biological Sciences, Queen's University, Belfast, UK
| | - Fiona Newberry
- Department of Biosciences, School of Science and Technology, Nottingham Trent University, Nottingham, UK
| | - Lesley Hoyles
- Department of Biosciences, School of Science and Technology, Nottingham Trent University, Nottingham, UK
| | - Sheila Patrick
- Institute for Global Food Security, School of Biological Sciences, Queen's University, Belfast, UK
- Wellcome Wolfson Institute for Experimental Medicine, School of Medicine, Dentistry and Biomedical Sciences, Queen's University Belfast, 97 Lisburn Road, Belfast, BT9 7BL, UK
| | - Linda Stewart
- Institute for Global Food Security, School of Biological Sciences, Queen's University, Belfast, UK
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6
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In Silico Study of Cell Surface Structures of Parabacteroides distasonis Involved in Its Maintenance within the Gut Microbiota. Int J Mol Sci 2022; 23:ijms23169411. [PMID: 36012685 PMCID: PMC9409006 DOI: 10.3390/ijms23169411] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2022] [Revised: 08/11/2022] [Accepted: 08/12/2022] [Indexed: 11/16/2022] Open
Abstract
The health-promoting Parabacteroides distasonis, which is part of the core microbiome, has recently received a lot of attention, showing beneficial properties for its host and potential as a new biotherapeutic product. However, no study has yet investigated the cell surface molecules and structures of P. distasonis that allow its maintenance within the gut microbiota. Moreover, although P. distasonis is strongly recognized as an intestinal commensal species with benefits for its host, several works displayed controversial results, showing it as an opportunistic pathogen. In this study, we reported gene clusters potentially involved in the synthesis of capsule, fimbriae-like and pili-like cell surface structures in 26 P. distasonis genomes and applied the new RfbA-typing classification in order to better understand and characterize the beneficial/pathogenic behavior related to P. distasonis strains. Two different types of fimbriae, three different types of pilus and up to fourteen capsular polysaccharide loci were identified over the 26 genomes studied. Moreover, the addition of data to the rfbA-type classification modified the outcome by rearranging rfbA genes and adding a fifth group to the classification. In conclusion, the strain variability in terms of external proteinaceous structure could explain the inter-strain differences previously observed of P. distasonis adhesion capacities and its potential pathogenicity, but no specific structure related to P. distasonis beneficial or detrimental activity was identified.
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7
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Slack E, Diard M. Resistance is futile? Mucosal immune mechanisms in the context of microbial ecology and evolution. Mucosal Immunol 2022; 15:1188-1198. [PMID: 36329192 PMCID: PMC9705250 DOI: 10.1038/s41385-022-00574-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2022] [Revised: 10/06/2022] [Accepted: 10/12/2022] [Indexed: 11/05/2022]
Abstract
In the beginning it was simple: we injected a protein antigen and studied the immune responses against the purified protein. This elegant toolbox uncovered thousands of mechanisms via which immune cells are activated. However, when we consider immune responses against real infectious threats, this elegant simplification misses half of the story: the infectious agents are typically evolving orders-of-magnitude faster than we are. Nowhere is this more pronounced than in the mammalian large intestine. A bacterium representing only 0.1% of the human gut microbiota will have a population size of 109 clones, each actively replicating. Moreover, the evolutionary pressure from other microbes is at least as profound as direct effects of the immune system. Therefore, to really understand intestinal immune mechanisms, we need to understand both the host response and how rapid microbial evolution alters the apparent outcome of the response. In this review we use the examples of intestinal inflammation and secretory immunoglobulin A (SIgA) to highlight what is already known (Fig. 1). Further, we will explore how these interactions can inform immunotherapy and prophylaxis. This has major implications for how we design effective mucosal vaccines against increasingly drug-resistant bacterial pathogens Fig. 1 THE IMMUNE RESPONSE SHAPES THE FITNESS LANDSCAPE IN THE GASTRO-INTESTINAL TRACT.: The red arrows depict possible evolutionary paths of a novel colonizer along adaptive peaks in the intestinal fitness landscapes that change with the status of the host immune system. The flat surfaces represent the non-null fitness baselines (values x or y) at which a bacterium can establish at minimum carrying capacity. a In the healthy gut, metabolic competence, resistance to aggressions by competitors and predators, swift adaptation to rapid fluctuations as well as surviving acidic pH and the flow of the intestinal content, represent potent selective pressures and as many opportunities for bacteria to increase fitness by phenotypic or genetic variations. b When pathogens trigger acute inflammation, bacteria must adapt to iron starvation, killing by immune cells and antimicrobial peptides, and oxidative stress, while new metabolic opportunities emerge. c When high-affinity SIgA are produced against a bacterium, e.g., after oral vaccination, escape of SIgA by altering or losing surface epitopes becomes crucial for maximum fitness. However, escaping polyvalent SIgA responses after vaccination with "evolutionary trap" vaccines leads to evolutionary trade-offs: A fitness maximum is reached in the vaccinated host gut that represents a major disadvantage for transmission into naïve hosts (fitness diminished below x) (d).
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Affiliation(s)
- Emma Slack
- Laboratory for Mucosal Immunology, Institute for Food, Nutrition and Health, D-HEST, ETH Zürich, Zürich, Switzerland.
- Botnar Research Institute for Child Health, Basel, Switzerland.
| | - Médéric Diard
- Botnar Research Institute for Child Health, Basel, Switzerland.
- Biozentrum, University of Basel, Basel, Switzerland.
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8
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Smith BJ, Li X, Shi ZJ, Abate A, Pollard KS. Scalable Microbial Strain Inference in Metagenomic Data Using StrainFacts. FRONTIERS IN BIOINFORMATICS 2022; 2:867386. [PMID: 36304283 PMCID: PMC9580935 DOI: 10.3389/fbinf.2022.867386] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2022] [Accepted: 04/14/2022] [Indexed: 11/25/2022] Open
Abstract
While genome databases are nearing a complete catalog of species commonly inhabiting the human gut, their representation of intraspecific diversity is lacking for all but the most abundant and frequently studied taxa. Statistical deconvolution of allele frequencies from shotgun metagenomic data into strain genotypes and relative abundances is a promising approach, but existing methods are limited by computational scalability. Here we introduce StrainFacts, a method for strain deconvolution that enables inference across tens of thousands of metagenomes. We harness a “fuzzy” genotype approximation that makes the underlying graphical model fully differentiable, unlike existing methods. This allows parameter estimates to be optimized with gradient-based methods, speeding up model fitting by two orders of magnitude. A GPU implementation provides additional scalability. Extensive simulations show that StrainFacts can perform strain inference on thousands of metagenomes and has comparable accuracy to more computationally intensive tools. We further validate our strain inferences using single-cell genomic sequencing from a human stool sample. Applying StrainFacts to a collection of more than 10,000 publicly available human stool metagenomes, we quantify patterns of strain diversity, biogeography, and linkage-disequilibrium that agree with and expand on what is known based on existing reference genomes. StrainFacts paves the way for large-scale biogeography and population genetic studies of microbiomes using metagenomic data.
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Affiliation(s)
- Byron J. Smith
- The Gladstone Institute of Data Science and Biotechnology, San Francisco, CA, United States
- Department of Epidemiology and Biostatistics, University of California, San Francisco, San Francisco, CA, United States
| | - Xiangpeng Li
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, San Francisco, CA, United States
| | - Zhou Jason Shi
- The Gladstone Institute of Data Science and Biotechnology, San Francisco, CA, United States
- Chan-Zuckerberg Biohub, San Francisco, CA, United States
| | - Adam Abate
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, San Francisco, CA, United States
- Chan-Zuckerberg Biohub, San Francisco, CA, United States
| | - Katherine S. Pollard
- The Gladstone Institute of Data Science and Biotechnology, San Francisco, CA, United States
- Department of Epidemiology and Biostatistics, University of California, San Francisco, San Francisco, CA, United States
- Chan-Zuckerberg Biohub, San Francisco, CA, United States
- *Correspondence: Katherine S. Pollard,
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Patrick S. A tale of two habitats: Bacteroides fragilis, a lethal pathogen and resident in the human gastrointestinal microbiome. Microbiology (Reading) 2022; 168. [DOI: 10.1099/mic.0.001156] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Bacteroides fragilis
is an obligately anaerobic Gram-negative bacterium and a major colonizer of the human large colon where
Bacteroides
is a predominant genus. During the growth of an individual clonal population, an astonishing number of reversible DNA inversion events occur, driving within-strain diversity. Additionally, the
B. fragilis
pan-genome contains a large pool of diverse polysaccharide biosynthesis loci, DNA restriction/modification systems and polysaccharide utilization loci, which generates remarkable between-strain diversity. Diversity clearly contributes to the success of
B. fragilis
within its normal habitat of the gastrointestinal (GI) tract and during infection in the extra-intestinal host environment. Within the GI tract,
B. fragilis
is usually symbiotic, for example providing localized nutrients for the gut epithelium, but
B. fragilis
within the GI tract may not always be benign. Metalloprotease toxin production is strongly associated with colorectal cancer.
B. fragilis
is unique amongst bacteria; some strains export a protein >99 % structurally similar to human ubiquitin and antigenically cross-reactive, which suggests a link to autoimmune diseases.
B. fragilis
is not a primary invasive enteric pathogen; however, if colonic contents contaminate the extra-intestinal host environment, it successfully adapts to this new habitat and causes infection; classically peritoneal infection arising from rupture of an inflamed appendix or GI surgery, which if untreated, can progress to bacteraemia and death. In this review selected aspects of
B. fragilis
adaptation to the different habitats of the GI tract and the extra-intestinal host environment are considered, along with the considerable challenges faced when studying this highly variable bacterium.
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Affiliation(s)
- Sheila Patrick
- Wellcome-Wolfson Institute for Experimental Medicine, School of Medicine, Dentistry and Biomedical Sciences Queen’s University Belfast, 97 Lisburn Rd, Belfast BT9 7BL, UK
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10
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Yan W, Hall AB, Jiang X. Bacteroidales species in the human gut are a reservoir of antibiotic resistance genes regulated by invertible promoters. NPJ Biofilms Microbiomes 2022; 8:1. [PMID: 35013297 PMCID: PMC8748976 DOI: 10.1038/s41522-021-00260-1] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2021] [Accepted: 11/26/2021] [Indexed: 12/21/2022] Open
Abstract
Antibiotic-resistance genes (ARGs) regulated by invertible promoters can mitigate the fitness cost of maintaining ARGs in the absence of antibiotics and could potentially prolong the persistence of ARGs in bacterial populations. However, the origin, prevalence, and distribution of these ARGs regulated by invertible promoters remains poorly understood. Here, we sought to assess the threat posed by ARGs regulated by invertible promoters by systematically searching for ARGs regulated by invertible promoters in the human gut microbiome and examining their origin, prevalence, and distribution. Through metagenomic assembly of 2227 human gut metagenomes and genomic analysis of the Unified Human Gastrointestinal Genome (UHGG) collection, we identified ARGs regulated by invertible promoters and categorized them into three classes based on the invertase-regulating phase variation. In the human gut microbiome, ARGs regulated by invertible promoters are exclusively found in Bacteroidales species. Through genomic analysis, we observed that ARGs regulated by invertible promoters have convergently originated from ARG insertions into glycan-synthesis loci that were regulated by invertible promoters at least three times. Moreover, all three classes of invertible promoters regulating ARGs are located within integrative conjugative elements (ICEs). Therefore, horizontal transfer via ICEs could explain the wide taxonomic distribution of ARGs regulated by invertible promoters. Overall, these findings reveal that glycan-synthesis loci regulated by invertible promoters in Bacteroidales species are an important hotspot for the emergence of clinically-relevant ARGs regulated by invertible promoters.
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Affiliation(s)
- Wei Yan
- National Library of Medicine, National Institutes of Health, Bethesda, Maryland, USA
| | - A Brantley Hall
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, Maryland, USA
- Center for Bioinformatics and Computational Biology, University of Maryland, College Park, Maryland, USA
| | - Xiaofang Jiang
- National Library of Medicine, National Institutes of Health, Bethesda, Maryland, USA.
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11
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The Application of Transposon Insertion Sequencing in Identifying Essential Genes in B. fragilis. Methods Mol Biol 2021. [PMID: 34709623 DOI: 10.1007/978-1-0716-1720-5_16] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
Abstract
Essential genes are those that are indispensable for the survival of organism under specific growth conditions. Investigating essential genes in pathogenic bacteria not only helps to understand vital biological networks but also provides novel targets for drug development. Availability of genetic engineering tools and high-throughput sequencing methods has enabled essential genes identification in many pathogenic gram-positive and gram-negative bacteria. Bacteroides fragilis is one of the major bacteria specific of human gastrointestinal microbiota. When B. fragilis moves out of its niche, it turns into deadly pathogen. Here, we describe detailed method for the essential gene identification in B. fragilis. Generated transposon mutant pool can be used for other applications such as identification of genes responsible for drug resistance in B. fragilis.
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12
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Analysis of six tonB gene homologs in Bacteroides fragilis revealed that tonB3 is essential for survival in experimental intestinal colonization and intra-abdominal infection. Infect Immun 2021; 90:e0046921. [PMID: 34662212 DOI: 10.1128/iai.00469-21] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The opportunistic, anaerobic pathogen and commensal of the human large intestinal tract, Bacteroides fragilis strain 638R, contains six predicted TonB proteins, termed TonB1-6, four ExbBs orthologs, ExbB1-4, and five ExbDs orthologs, ExbD1-5. The inner membrane TonB/ExbB/ExbD complex harvests energy from the proton motive force (Δp) and the TonB C-terminal domain interacts with and transduces energy to outer membrane TonB-dependent transporters (TBDTs). However, TonB's role in activating nearly one hundred TBDTs for nutrient acquisition in B. fragilis during intestinal colonization and extraintestinal infection has not been established. In this study, we show that growth was abolished in the ΔtonB3 mutant when heme, vitamin B12, Fe(III)-ferrichrome, starch, mucin-glycans, or N-linked glycans were used as a substrate for growth in vitro. Genetic complementation of the ΔtonB3 mutant with the tonB3 gene restored growth on these substrates. The ΔtonB1, ΔtonB2, ΔtonB4, ΔtonB5, and ΔtonB6 single mutants did not show a growth defect. This indicates that there was no functional compensation for the lack of TonB3, and it demonstrates that TonB3, alone, drives the TBDTs involved in the transport of essential nutrients. The ΔtonB3 mutant had a severe growth defect in a mouse model of intestinal colonization compared to the parent strain. This intestinal growth defect was enhanced in the ΔtonB3 ΔtonB6 double mutant strain which completely lost its ability to colonize the mouse intestinal tract compared to the parent strain. The ΔtonB1, ΔtonB2, ΔtonB4, and ΔtonB5 mutants did not significantly affect intestinal colonization. Moreover, the survival of the ΔtonB3 mutant strain was completely eradicated in a rat model of intra-abdominal infection. Taken together, these findings show that TonB3 was essential for survival in vivo. The genetic organization of tonB1, tonB2, tonB4, tonB5, and tonB6 gene orthologs indicates that they may interact with periplasmic and nonreceptor outer membrane proteins, but the physiological relevance of this has not been defined. Because anaerobic fermentation metabolism yields a lower Δp than aerobic respiration and B. fragilis has a reduced redox state in its periplasmic space - in contrast to an oxidative environment in aerobes - it remains to be determined if the diverse system of TonB/ExbB/ExbD orthologs encoded by B. fragilis have an increased sensitivity to PMF (relative to aerobic bacteria) to allow for the harvesting of energy under anaerobic conditions.
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Chamarande J, Cunat L, Caillet C, Mathieu L, Duval JFL, Lozniewski A, Frippiat JP, Alauzet C, Cailliez-Grimal C. Surface Properties of Parabacteroides distasonis and Impacts of Stress-Induced Molecules on Its Surface Adhesion and Biofilm Formation Capacities. Microorganisms 2021; 9:1602. [PMID: 34442682 PMCID: PMC8400631 DOI: 10.3390/microorganisms9081602] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2021] [Revised: 07/22/2021] [Accepted: 07/26/2021] [Indexed: 12/11/2022] Open
Abstract
The gut microbiota is a complex and dynamic ecosystem whose balance and homeostasis are essential to the host's well-being and whose composition can be critically affected by various factors, including host stress. Parabacteroides distasonis causes well-known beneficial roles for its host, but is negatively impacted by stress. However, the mechanisms explaining its maintenance in the gut have not yet been explored, in particular its capacities to adhere onto (bio)surfaces, form biofilms and the way its physicochemical surface properties are affected by stressing conditions. In this paper, we reported adhesion and biofilm formation capacities of 14 unrelated strains of P. distasonis using a steam-based washing procedure, and the electrokinetic features of its surface. Results evidenced an important inter-strain variability for all experiments including the response to stress hormones. In fact, stress-induced molecules significantly impact P. distasonis adhesion and biofilm formation capacities in 35% and 23% of assays, respectively. This study not only provides basic data on the adhesion and biofilm formation capacities of P. distasonis to abiotic substrates but also paves the way for further research on how stress-molecules could be implicated in P. distasonis maintenance within the gut microbiota, which is a prerequisite for designing efficient solutions to optimize its survival within gut environment.
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Affiliation(s)
- Jordan Chamarande
- SIMPA, Université de Lorraine, F-54000 Nancy, France; (J.C.); (L.C.); (A.L.); (J.-P.F.); (C.A.)
| | - Lisiane Cunat
- SIMPA, Université de Lorraine, F-54000 Nancy, France; (J.C.); (L.C.); (A.L.); (J.-P.F.); (C.A.)
| | - Céline Caillet
- CNRS, LIEC, Université de Lorraine, F-54000 Nancy, France; (C.C.); (J.F.L.D.)
| | - Laurence Mathieu
- Ecole Pratique des Hautes Etudes (EPHE), Laboratoire de Chimie Physique et Microbiologie pour les Matériaux et l’Environnement (LCPME), Paris Sciences Lettres University (PSL), F-54500 Nancy, France;
| | - Jérôme F. L. Duval
- CNRS, LIEC, Université de Lorraine, F-54000 Nancy, France; (C.C.); (J.F.L.D.)
| | - Alain Lozniewski
- SIMPA, Université de Lorraine, F-54000 Nancy, France; (J.C.); (L.C.); (A.L.); (J.-P.F.); (C.A.)
- CHRU de Nancy, Service de Microbiologie, F-54000 Nancy, France
| | - Jean-Pol Frippiat
- SIMPA, Université de Lorraine, F-54000 Nancy, France; (J.C.); (L.C.); (A.L.); (J.-P.F.); (C.A.)
| | - Corentine Alauzet
- SIMPA, Université de Lorraine, F-54000 Nancy, France; (J.C.); (L.C.); (A.L.); (J.-P.F.); (C.A.)
- CHRU de Nancy, Service de Microbiologie, F-54000 Nancy, France
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14
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Kirsch JM, Brzozowski RS, Faith D, Round JL, Secor PR, Duerkop BA. Bacteriophage-Bacteria Interactions in the Gut: From Invertebrates to Mammals. Annu Rev Virol 2021; 8:95-113. [PMID: 34255542 DOI: 10.1146/annurev-virology-091919-101238] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Bacteria and their viruses (bacteriophages or phages) interact antagonistically and beneficially in polymicrobial communities such as the guts of animals. These interactions are multifaceted and are influenced by environmental conditions. In this review, we discuss phage-bacteria interactions as they relate to the complex environment of the gut. Within the mammalian and invertebrate guts, phages and bacteria engage in diverse interactions including genetic coexistence through lysogeny, and phages directly modulate microbiota composition and the immune system with consequences that are becoming recognized as potential drivers of health and disease. With greater depth of understanding of phage-bacteria interactions in the gut and the outcomes, future phage therapies become possible. Expected final online publication date for the Annual Review of Virology, Volume 8 is September 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
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Affiliation(s)
- Joshua M Kirsch
- Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, Colorado 80045, USA;
| | - Robert S Brzozowski
- Division of Biological Sciences, University of Montana, Missoula, Montana 59812, USA;
| | - Dominick Faith
- Division of Biological Sciences, University of Montana, Missoula, Montana 59812, USA;
| | - June L Round
- Department of Pathology, Division of Microbiology and Immunology, University of Utah School of Medicine, Salt Lake City, Utah 84113, USA;
| | - Patrick R Secor
- Division of Biological Sciences, University of Montana, Missoula, Montana 59812, USA;
| | - Breck A Duerkop
- Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, Colorado 80045, USA;
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15
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Campbell DE, Ly LK, Ridlon JM, Hsiao A, Whitaker RJ, Degnan PH. Infection with Bacteroides Phage BV01 Alters the Host Transcriptome and Bile Acid Metabolism in a Common Human Gut Microbe. Cell Rep 2021; 32:108142. [PMID: 32937127 PMCID: PMC8354205 DOI: 10.1016/j.celrep.2020.108142] [Citation(s) in RCA: 42] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2020] [Revised: 07/07/2020] [Accepted: 08/21/2020] [Indexed: 12/16/2022] Open
Abstract
Gut-associated phages are hypothesized to alter the abundance and activity of their bacterial hosts, contributing to human health and disease. Although temperate phages constitute a significant fraction of the gut virome, the effects of lysogenic infection are underexplored. We report that the temperate phage, Bacteroides phage BV01, broadly alters its host's transcriptome, the prominent human gut symbiont Bacteroides vulgatus. This alteration occurs through phage-induced repression of a tryptophan-rich sensory protein (TspO) and represses bile acid deconjugation. Because microbially modified bile acids are important signals for the mammalian host, this is a mechanism by which a phage may influence mammalian phenotypes. Furthermore, BV01 and its relatives in the proposed phage family Salyersviridae are ubiquitous in human gut metagenomes, infecting a broad range of Bacteroides hosts. These results demonstrate the complexity of phage-bacteria-mammal relationships and emphasize a need to better understand the role of temperate phages in the gut microbiome.
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Affiliation(s)
| | - Lindsey K Ly
- Division of Nutritional Sciences, University of Illinois, Urbana, IL 61801, USA; Department of Animal Sciences, University of Illinois, Urbana, IL 61801, USA
| | - Jason M Ridlon
- Division of Nutritional Sciences, University of Illinois, Urbana, IL 61801, USA; Department of Animal Sciences, University of Illinois, Urbana, IL 61801, USA; Carl R. Woese Institute for Genomic Biology, University of Illinois, Urbana, IL 61801, USA
| | - Ansel Hsiao
- Department of Microbiology and Plant Pathology, University of California, Riverside, Riverside, CA 92521, USA
| | - Rachel J Whitaker
- Department of Microbiology, University of Illinois, Urbana, IL 61801, USA; Carl R. Woese Institute for Genomic Biology, University of Illinois, Urbana, IL 61801, USA
| | - Patrick H Degnan
- Department of Microbiology and Plant Pathology, University of California, Riverside, Riverside, CA 92521, USA.
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16
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Affiliation(s)
- Hannah C. Carrow
- Department of Pathology, University of California San Diego, La Jolla, California, United States of America
| | - Lakshmi E. Batachari
- Department of Pathology, University of California San Diego, La Jolla, California, United States of America
| | - Hiutung Chu
- Department of Pathology, University of California San Diego, La Jolla, California, United States of America
- Chiba University-UC San Diego Center for Mucosal Immunology, Allergy, and Vaccine, La Jolla, California, United States of America
- Humans and the Microbiome Program, CIFAR, Toronto, Ontario, Canada
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17
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Yekani M, Baghi HB, Naghili B, Vahed SZ, Sóki J, Memar MY. To resist and persist: Important factors in the pathogenesis of Bacteroides fragilis. Microb Pathog 2020; 149:104506. [PMID: 32950639 DOI: 10.1016/j.micpath.2020.104506] [Citation(s) in RCA: 42] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2020] [Revised: 07/15/2020] [Accepted: 09/15/2020] [Indexed: 02/07/2023]
Abstract
Bacteroides fragilis is a most frequent anaerobic pathogen isolated from human infections, particularly found in the abdominal cavity. Different factors contribute to the pathogenesis and persistence of B. fragilis at infection sites. The knowledge of the virulence factors can provide applicable information for finding alternative options for the antibiotic therapy and treatment of B. fragilis caused infections. Herein, a comprehensive review of the important B. fragilis virulence factors was prepared. In addition to B. fragilis toxin (BFT) and its potential role in the diarrhea and cancer development, some other important virulence factors and characteristics of B. fragilis are described including capsular polysaccharides, iron acquisition, resistance to antimicrobial agents, and survival during the prolonged oxidative stress, quorum sensing, and secretion systems.
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Affiliation(s)
- Mina Yekani
- Department of Microbiology, Faculty of Medicine, Kashan University of Medical Sciences, Kashan, Iran; Student Research Committee,Kashan University of Medical Sciences, Kashan, Iran
| | - Hossein Bannazadeh Baghi
- Infectious and Tropical Diseases Research Center, Tabriz University of Medical Sciences, Tabriz, Iran; Immunology Research Center, Tabriz University of Medical Sciences, Tabriz, Iran
| | - Behrooz Naghili
- Infectious and Tropical Diseases Research Center, Tabriz University of Medical Sciences, Tabriz, Iran
| | | | - József Sóki
- Institute of Clinical Microbiology, Faculty of Medicine, University of Szeged, Szeged, Hungary.
| | - Mohammad Yousef Memar
- Infectious and Tropical Diseases Research Center, Tabriz University of Medical Sciences, Tabriz, Iran; Microbiology Department, School of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran; Students' Research Committee, Tabriz University of Medical Sciences, Tabriz, Iran.
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18
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Porter NT, Hryckowian AJ, Merrill BD, Fuentes JJ, Gardner JO, Glowacki RWP, Singh S, Crawford RD, Snitkin ES, Sonnenburg JL, Martens EC. Phase-variable capsular polysaccharides and lipoproteins modify bacteriophage susceptibility in Bacteroides thetaiotaomicron. Nat Microbiol 2020; 5:1170-1181. [PMID: 32601452 PMCID: PMC7482406 DOI: 10.1038/s41564-020-0746-5] [Citation(s) in RCA: 83] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2019] [Accepted: 05/27/2020] [Indexed: 12/22/2022]
Abstract
A variety of cell surface structures dictate interactions between bacteria and their environment, including their viruses (bacteriophages). Members of the human gut Bacteroidetes characteristically produce several phase-variable capsular polysaccharides (CPSs), but their contributions to bacteriophage interactions are unknown. To begin to understand how CPSs have an impact on Bacteroides-phage interactions, we isolated 71 Bacteroides thetaiotaomicron-infecting bacteriophages from two locations in the United States. Using B. thetaiotaomicron strains that express defined subsets of CPSs, we show that CPSs dictate host tropism for these phages and that expression of non-permissive CPS variants is selected under phage predation, enabling survival. In the absence of CPSs, B. thetaiotaomicron escapes bacteriophage predation by altering expression of eight distinct phase-variable lipoproteins. When constitutively expressed, one of these lipoproteins promotes resistance to multiple bacteriophages. Our results reveal important roles for Bacteroides CPSs and other cell surface structures that allow these bacteria to persist under bacteriophage predation, and hold important implications for using bacteriophages therapeutically to target gut symbionts.
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Affiliation(s)
- Nathan T Porter
- Department of Microbiology and Immunology, University of Michigan, Ann Arbor, MI, USA
| | - Andrew J Hryckowian
- Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, CA, USA.
| | - Bryan D Merrill
- Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, CA, USA
| | - Jaime J Fuentes
- Department of Microbiology and Immunology, University of Michigan, Ann Arbor, MI, USA
| | - Jackson O Gardner
- Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, CA, USA
| | - Robert W P Glowacki
- Department of Microbiology and Immunology, University of Michigan, Ann Arbor, MI, USA
| | - Shaleni Singh
- Department of Microbiology and Immunology, University of Michigan, Ann Arbor, MI, USA
| | - Ryan D Crawford
- Department of Computational Medicine and Bioinformatics, University of Michigan, Ann Arbor, MI, USA
| | - Evan S Snitkin
- Department of Microbiology and Immunology, University of Michigan, Ann Arbor, MI, USA
| | - Justin L Sonnenburg
- Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, CA, USA
| | - Eric C Martens
- Department of Microbiology and Immunology, University of Michigan, Ann Arbor, MI, USA.
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19
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Comprehensive analysis of chromosomal mobile genetic elements in the gut microbiome reveals phylum-level niche-adaptive gene pools. PLoS One 2019; 14:e0223680. [PMID: 31830054 PMCID: PMC6907783 DOI: 10.1371/journal.pone.0223680] [Citation(s) in RCA: 51] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2019] [Accepted: 09/25/2019] [Indexed: 12/16/2022] Open
Abstract
Mobile genetic elements (MGEs) drive extensive horizontal transfer in the gut microbiome. This transfer could benefit human health by conferring new metabolic capabilities to commensal microbes, or it could threaten human health by spreading antibiotic resistance genes to pathogens. Despite their biological importance and medical relevance, MGEs from the gut microbiome have not been systematically characterized. Here, we present a comprehensive analysis of chromosomal MGEs in the gut microbiome using a method that enables the identification of the mobilizable unit of MGEs. We curated a database of 5,219 putative MGEs encompassing seven MGE classes called ImmeDB. We observed that many MGEs carry genes that could confer an adaptive advantage to the gut environment including gene families involved in antibiotic resistance, bile salt detoxification, mucus degradation, capsular polysaccharide biosynthesis, polysaccharide utilization, and sporulation. We find that antibiotic resistance genes are more likely to be spread by conjugation via integrative conjugative elements or integrative mobilizable elements than transduction via prophages. Horizontal transfer of MGEs is extensive within phyla but rare across phyla, supporting phylum level niche-adaptive gene pools in the gut microbiome. ImmeDB will be a valuable resource for future studies on the gut microbiome and MGE communities.
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20
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Sydenham TV, Overballe-Petersen S, Hasman H, Wexler H, Kemp M, Justesen US. Complete hybrid genome assembly of clinical multidrug-resistant Bacteroides fragilis isolates enables comprehensive identification of antimicrobial-resistance genes and plasmids. Microb Genom 2019; 5:e000312. [PMID: 31697231 PMCID: PMC6927303 DOI: 10.1099/mgen.0.000312] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2019] [Accepted: 10/17/2019] [Indexed: 02/06/2023] Open
Abstract
Bacteroides fragilis constitutes a significant part of the normal human gut microbiota and can also act as an opportunistic pathogen. Antimicrobial resistance (AMR) and the prevalence of AMR genes are increasing, and prediction of antimicrobial susceptibility based on sequence information could support targeted antimicrobial therapy in a clinical setting. Complete identification of insertion sequence (IS) elements carrying promoter sequences upstream of resistance genes is necessary for prediction of AMR. However, de novo assemblies from short reads alone are often fractured due to repeat regions and the presence of multiple copies of identical IS elements. Identification of plasmids in clinical isolates can aid in the surveillance of the dissemination of AMR, and comprehensive sequence databases support microbiome and metagenomic studies. We tested several short-read, hybrid and long-lead assembly pipelines by assembling the type strain B. fragilis CCUG4856T (=ATCC25285=NCTC9343) with Illumina short reads and long reads generated by Oxford Nanopore Technologies (ONT) MinION sequencing. Hybrid assembly with Unicycler, using quality filtered Illumina reads and Filtlong filtered and Canu-corrected ONT reads, produced the assembly of highest quality. This approach was then applied to six clinical multidrug-resistant B. fragilis isolates and, with minimal manual finishing of chromosomal assemblies of three isolates, complete, circular assemblies of all isolates were produced. Eleven circular, putative plasmids were identified in the six assemblies, of which only three corresponded to a known cultured Bacteroides plasmid. Complete IS elements could be identified upstream of AMR genes; however, there was not complete correlation between the absence of IS elements and antimicrobial susceptibility. As our knowledge on factors that increase expression of resistance genes in the absence of IS elements is limited, further research is needed prior to implementing AMR prediction for B. fragilis from whole-genome sequencing.
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Affiliation(s)
- Thomas V. Sydenham
- Research Unit of Clinical Microbiology, Department of Clinical Research, University of Southern Denmark, Odense, Denmark
- Department of Clinical Microbiology, Odense University Hospital, Odense, Denmark
- Department of Clinical Microbiology, Lillebaelt Hospital, Vejle, Denmark
| | | | - Henrik Hasman
- Bacteria, Parasites and Fungi, Statens Serum Institut, Copenhagen, Denmark
| | - Hannah Wexler
- GLAVA Health Care System and David Geffen School of Medicine, UCLA (University of California, Los Angeles), Los Angeles, CA, USA
| | - Michael Kemp
- Research Unit of Clinical Microbiology, Department of Clinical Research, University of Southern Denmark, Odense, Denmark
- Department of Clinical Microbiology, Odense University Hospital, Odense, Denmark
| | - Ulrik S. Justesen
- Research Unit of Clinical Microbiology, Department of Clinical Research, University of Southern Denmark, Odense, Denmark
- Department of Clinical Microbiology, Odense University Hospital, Odense, Denmark
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21
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Husain F, Tang K, Veeranagouda Y, Boente R, Patrick S, Blakely G, Wexler HM. Novel large-scale chromosomal transfer in Bacteroides fragilis contributes to its pan-genome and rapid environmental adaptation. Microb Genom 2019; 3. [PMID: 29208130 PMCID: PMC5729914 DOI: 10.1099/mgen.0.000136] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Bacteroides fragilis, an important component of the human gastrointestinal microbiota, can cause lethal extra-intestinal infection upon escape from the gastrointestinal tract. We demonstrated transfer and recombination of large chromosomal segments from B. fragilis HMW615, a multidrug resistant clinical isolate, to B. fragilis 638R. In one example, the transfer of a segment of ~435 Kb/356 genes replaced ~413 Kb/326 genes of the B. fragilis 638R chromosome. In addition to transfer of antibiotic resistance genes, these transfers (1) replaced complete divergent polysaccharide biosynthesis loci; (2) replaced DNA inversion-controlled intergenic shufflons (that control expression of genes encoding starch utilization system outer membrane proteins) with more complex, divergent shufflons; and (3) introduced additional intergenic shufflons encoding divergent Type 1 restriction/modification systems. Conjugative transposon-like genes within a transferred segment and within a putative integrative conjugative element (ICE5) ~45 kb downstream from the transferred segment both encode proteins that may be involved in the observed transfer. These data indicate that chromosomal transfer is a driver of antigenic diversity and nutrient adaptation in Bacteroides that (1) contributes to the dissemination of the extensive B. fragilis pan-genome, (2) allows rapid adaptation to a changing environment and (3) can confer pathogenic characteristics to host symbionts.
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Affiliation(s)
- Fasahath Husain
- Brentwood Biomedical Research Institute, Los Angeles, CA, USA
| | | | | | | | | | | | - Hannah M. Wexler
- Research, GLAVAHCS, 11301 Wilshire Blvd., 691/151J Bldg. 115, Room 312, Los Angeles, CA, USA
- *Correspondence: Hannah M. Wexler,
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22
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Neumann G, Wall R, Rangel I, Marques TM, Repsilber D. Qualitative modelling of the interplay of inflammatory status and butyrate in the human gut: a hypotheses about robust bi-stability. BMC SYSTEMS BIOLOGY 2018; 12:144. [PMID: 30558589 PMCID: PMC6296070 DOI: 10.1186/s12918-018-0667-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/27/2018] [Accepted: 11/21/2018] [Indexed: 02/10/2023]
Abstract
Background Gut microbiota interacts with the human gut in multiple ways. Microbiota composition is altered in inflamed gut conditions. Likewise, certain microbial fermentation products as well as the lipopolysaccharides of the outer membrane are examples of microbial products with opposing influences on gut epithelium inflammation status. This system of intricate interactions is known to play a core role in human gut inflammatory diseases. Here, we present and analyse a simplified model of bidirectional interaction between the microbiota and the host: in focus is butyrate as an example for a bacterial fermentation product with anti-inflammatory properties. Results We build a dynamical model based on an existing model of inflammatory regulation in gut epithelial cells. Our model introduces both butyrate as a bacterial product which counteracts inflammation, as well as bacterial LPS as a pro-inflammatory bacterial product. Moreover, we propose an extension of this model that also includes a feedback interaction towards bacterial composition. The analysis of these dynamical models shows robust bi-stability driven by butyrate concentrations in the gut. The extended model hints towards a further possible enforcement of the observed bi-stability via alteration of gut bacterial composition. A theoretical perspective on the stability of the described switch-like character is discussed. Conclusions Interpreting the results of this qualitative model allows formulating hypotheses about the switch-like character of inflammatory regulation in the gut epithelium, involving bacterial products as constitutive parts of the system. We also speculate about possible explanations for observed bimodal distributions in bacterial compositions in the human gut. The switch-like behaviour of the system proved to be mostly independent of parameter choices. Further implications of the qualitative character of our modeling approach for the robustness of the proposed hypotheses are discussed, as well as the pronounced role of butyrate compared to other inflammatory regulators, especially LPS, NF- κB and cytokines. Electronic supplementary material The online version of this article (10.1186/s12918-018-0667-6) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Gunter Neumann
- School of Medical Health (MV), Örebro University, Örebro, 70182, Sweden
| | - Rebecca Wall
- School of Medical Health (MV), Örebro University, Örebro, 70182, Sweden
| | - Ignacio Rangel
- School of Medical Health (MV), Örebro University, Örebro, 70182, Sweden
| | - Tatiana M Marques
- School of Medical Health (MV), Örebro University, Örebro, 70182, Sweden
| | - Dirk Repsilber
- School of Medical Health (MV), Örebro University, Örebro, 70182, Sweden.
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23
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Stewart L, D M Edgar J, Blakely G, Patrick S. Antigenic mimicry of ubiquitin by the gut bacterium Bacteroides fragilis: a potential link with autoimmune disease. Clin Exp Immunol 2018; 194:153-165. [PMID: 30076785 PMCID: PMC6194340 DOI: 10.1111/cei.13195] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2018] [Revised: 07/18/2018] [Accepted: 07/28/2018] [Indexed: 01/09/2023] Open
Abstract
Ubiquitin is highly conserved across eukaryotes and is essential for normal eukaryotic cell function. The bacterium Bacteroides fragilis is a member of the normal human gut microbiota, and the only bacterium known to encode a homologue of eukaryotic ubiquitin. The B. fragilis gene sequence indicates a past horizontal gene transfer event from a eukaryotic source. It encodes a protein (BfUbb) with 63% identity to human ubiquitin which is exported from the bacterial cell. The aim of this study was (i) to determine if there was antigenic cross‐reactivity between B. fragilis ubiquitin and human ubiquitin and (ii) to determine if humans produced antibodies to BfUbb. Molecular model comparisons of BfUbb and human ubiquitin predicted a high level (99·8% confidence) of structural similarity. Linear epitope mapping identified epitopes in BfUbb and human ubiquitin that cross‐react. BfUbb also has epitope(s) that do not cross‐react with human ubiquitin. The reaction of human serum (n = 474) to BfUbb and human ubiquitin from the following four groups of subjects was compared by enzyme‐linked immunosorbent assay (ELISA): (1) newly autoantibody‐positive patients, (2) allergen‐specific immunoglobulin (Ig)E‐negative patients, (3) ulcerative colitis patients and (4) healthy volunteers. We show that the immune system of some individuals has been exposed to BfUbb which has resulted in the generation of IgG antibodies. Serum from patients referred for first‐time testing to an immunology laboratory for autoimmune disease are more likely to have a high level of antibodies to BfUbb than healthy volunteers. Molecular mimicry of human ubiquitin by BfUbb could be a trigger for autoimmune disease.
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Affiliation(s)
- L Stewart
- School School of Biological Sciences, Queen's University Belfast, Belfast, UK
| | - J D M Edgar
- Regional Immunology Laboratory, Belfast Health and Social Care Trust, Belfast, UK.,The Wellcome-Wolfson Institute for Experimental Medicine, Queen's University Belfast, Belfast, UK
| | - G Blakely
- School of Biological Sciences, University of Edinburgh, Edinburgh, UK
| | - S Patrick
- School of Biological Sciences, University of Edinburgh, Edinburgh, UK.,The Wellcome-Wolfson Institute for Experimental Medicine, Queen's University Belfast, Belfast, UK
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Costea PI, Coelho LP, Sunagawa S, Munch R, Huerta-Cepas J, Forslund K, Hildebrand F, Kushugulova A, Zeller G, Bork P. Subspecies in the global human gut microbiome. Mol Syst Biol 2017; 13:960. [PMID: 29242367 PMCID: PMC5740502 DOI: 10.15252/msb.20177589] [Citation(s) in RCA: 86] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2017] [Revised: 11/24/2017] [Accepted: 11/29/2017] [Indexed: 02/06/2023] Open
Abstract
Population genomics of prokaryotes has been studied in depth in only a small number of primarily pathogenic bacteria, as genome sequences of isolates of diverse origin are lacking for most species. Here, we conducted a large-scale survey of population structure in prevalent human gut microbial species, sampled from their natural environment, with a culture-independent metagenomic approach. We examined the variation landscape of 71 species in 2,144 human fecal metagenomes and found that in 44 of these, accounting for 72% of the total assigned microbial abundance, single-nucleotide variation clearly indicates the existence of sub-populations (here termed subspecies). A single subspecies (per species) usually dominates within each host, as expected from ecological theory. At the global scale, geographic distributions of subspecies differ between phyla, with Firmicutes subspecies being significantly more geographically restricted. To investigate the functional significance of the delineated subspecies, we identified genes that consistently distinguish them in a manner that is independent of reference genomes. We further associated these subspecies-specific genes with properties of the microbial community and the host. For example, two of the three Eubacterium rectale subspecies consistently harbor an accessory pro-inflammatory flagellum operon that is associated with lower gut community diversity, higher host BMI, and higher blood fasting insulin levels. Using an additional 676 human oral samples, we further demonstrate the existence of niche specialized subspecies in the different parts of the oral cavity. Taken together, we provide evidence for subspecies in the majority of abundant gut prokaryotes, leading to a better functional and ecological understanding of the human gut microbiome in conjunction with its host.
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Affiliation(s)
- Paul I Costea
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Luis Pedro Coelho
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Shinichi Sunagawa
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany
- Department of Biology, Institute of Microbiology, ETH Zurich, Zurich, Switzerland
| | - Robin Munch
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Jaime Huerta-Cepas
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Kristoffer Forslund
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Falk Hildebrand
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | | | - Georg Zeller
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Peer Bork
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany
- Max-Delbrück-Centre for Molecular Medicine, Berlin, Germany
- Molecular Medicine Partnership Unit, Heidelberg, Germany
- Department of Bioinformatics, Biocenter, University of Würzburg, Würzburg, Germany
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Tajkarimi M, Wexler HM. CRISPR-Cas Systems in Bacteroides fragilis, an Important Pathobiont in the Human Gut Microbiome. Front Microbiol 2017; 8:2234. [PMID: 29218031 PMCID: PMC5704556 DOI: 10.3389/fmicb.2017.02234] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2017] [Accepted: 10/31/2017] [Indexed: 12/29/2022] Open
Abstract
Background: While CRISPR-Cas systems have been identified in bacteria from a wide variety of ecological niches, there are no studies to describe CRISPR-Cas elements in Bacteroides species, the most prevalent anaerobic bacteria in the lower intestinal tract. Microbes of the genus Bacteroides make up ~25% of the total gut microbiome. Bacteroides fragilis comprises only 2% of the total Bacteroides in the gut, yet causes of >70% of Bacteroides infections. The factors causing it to transition from benign resident of the gut microbiome to virulent pathogen are not well understood, but a combination of horizontal gene transfer (HGT) of virulence genes and differential transcription of endogenous genes are clearly involved. The CRISPR-Cas system is a multi-functional system described in prokaryotes that may be involved in control both of HGT and of gene regulation. Results: Clustered regularly interspaced short palindromic repeats (CRISPR) elements in all strains of B. fragilis (n = 109) with publically available genomes were identified. Three different CRISPR-Cas types, corresponding most closely to Type IB, Type IIIB, and Type IIC, were identified. Thirty-five strains had two CRISPR-Cas types, and three strains included all three CRISPR-Cas types in their respective genomes. The cas1 gene in the Type IIIB system encoded a reverse-transcriptase/Cas1 fusion protein rarely found in prokaryotes. We identified a short CRISPR (3 DR) with no associated cas genes present in most of the isolates; these CRISPRs were found immediately upstream of a hipA/hipB operon and we speculate that this element may be involved in regulation of this operon related to formation of persister cells during antimicrobial exposure. Also, blood isolates of B. fragilis did not have Type IIC CRISPR-Cas systems and had atypical Type IIIB CRISPR-Cas systems that were lacking adjacent cas genes. Conclusions: This is the first systematic report of CRISPR-Cas systems in a wide range of B. fragilis strains from a variety of sources. There are four apparent CRISPR-Cas systems in B. fragilis-three systems have adjacent cas genes. Understanding CRISPR/Cas function in B. fragilis will elucidate their role in gene expression, DNA repair and ability to survive exposure to antibiotics. Also, based on their unique CRISPR-Cas arrays, their phylogenetic clustering and their virulence potential, we are proposing that blood isolates of B. fragilis be viewed a separate subgroup.
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Affiliation(s)
- Mehrdad Tajkarimi
- Brentwood Biomedical Research Institute, Los Angeles, CA, United States
| | - Hannah M. Wexler
- Brentwood Biomedical Research Institute, Los Angeles, CA, United States
- University of California, Los Angeles, Los Angeles, CA, United States
- GLAVA Health Care System, Los Angeles, CA, United States
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Porter NT, Canales P, Peterson DA, Martens EC. A Subset of Polysaccharide Capsules in the Human Symbiont Bacteroides thetaiotaomicron Promote Increased Competitive Fitness in the Mouse Gut. Cell Host Microbe 2017; 22:494-506.e8. [PMID: 28966055 PMCID: PMC5830307 DOI: 10.1016/j.chom.2017.08.020] [Citation(s) in RCA: 73] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2017] [Revised: 05/25/2017] [Accepted: 08/29/2017] [Indexed: 02/08/2023]
Abstract
Capsular polysaccharides (CPSs) play multiple roles in protecting bacteria from host and environmental factors, and many commensal bacteria can produce multiple capsule types. To better understand the roles of different CPSs in competitive intestinal colonization, we individually expressed the eight different capsules of the human gut symbiont Bacteroides thetaiotaomicron. Certain CPSs were most advantageous in vivo, and increased anti-CPS immunoglobulin A correlated with increased fitness of a strain expressing one particular capsule, CPS5, suggesting that it promotes avoidance of adaptive immunity. A strain with the ability to switch between multiple capsules was more competitive than those expressing any single capsule except CPS5. After antibiotic perturbation, only the wild-type, capsule-switching strain remained in the gut, shifting to prominent expression of CPS5 only in mice with intact adaptive immunity. These data suggest that different capsules equip mutualistic gut bacteria with the ability to thrive in various niches, including those influenced by immune responses and antibiotic perturbations.
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Affiliation(s)
- Nathan T Porter
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI 48109, USA
| | - Pablo Canales
- Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Daniel A Peterson
- Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Eric C Martens
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI 48109, USA.
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27
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Abstract
The human intestine harbors a dense microbial ecosystem (microbiota) that is different between individuals, dynamic over time, and critical for aspects of health and disease. Dietary polysaccharides directly shape the microbiota because of a gap in human digestive physiology, which is equipped to assimilate only proteins, lipids, simple sugars, and starch, leaving nonstarch polysaccharides as major nutrients reaching the microbiota. A mutualistic role of gut microbes is to digest dietary complex carbohydrates, liberating host-absorbable energy via fermentation products. Emerging data indicate that polysaccharides play extensive roles in host-gut microbiota symbiosis beyond dietary polysaccharide digestion, including microbial interactions with endogenous host glycans and the importance of microbial polysaccharides. In this review, we consider multiple mechanisms through which polysaccharides mediate aspects of host-microbe symbiosis in the gut, including some affecting health. As host and microbial metabolic pathways are intimately connected with diet, we highlight the potential to manipulate this system for health.
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Affiliation(s)
- Nathan T Porter
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan 48109;
| | - Eric C Martens
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan 48109;
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28
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Akhi MT, Ghotaslou R, Alizadeh N, Yekani M, Beheshtirouy S, Asgharzadeh M, Pirzadeh T, Memar MY. nim gene-independent metronidazole-resistant Bacteroides fragilis in surgical site infections. GMS HYGIENE AND INFECTION CONTROL 2017; 12:Doc13. [PMID: 28840093 PMCID: PMC5564006 DOI: 10.3205/dgkh000298] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Background:Bacteroides fragilis is the most common anaerobic pathogen isolated from surgical site infections (SSIs). Metronidazole resistance is increasing and the mechanisms of resistance are not clear in some isolates. The aim of the present study was to investigate the metronidazole susceptibility prevalence, and detect nim genes in B. fragilis isolates from SSIs. Methods: This study included 100 surgery patients with signs and symptoms indicative of SSIs. Syringe aspiration of the infected site was used to collect specimens. All specimens were cultured on BBA (Brucella blood agar), KVLB (kanamycin-vancomycin laked blood), and BBE (Bacteroides bile esculin) agar. The MIC (minimum inhibitory concentration) of metronidazole was determined by the agar dilution method according to the Clinical and Laboratory Standard Institute (CLSI). Then the PCR method was used to determine the presence of the nim gene. Results: In the present study, 26 B. fragilis were isolated from 100 SSIs specimens. Eight isolates were metronidazole resistant; the metronidazole MIC was 32 µg/mL for 7 isolates and 64 µg/mL for one isolate. All isolates were nim gene negative. Conclusion: The emergence of metronidazole-resistant B. fragilis limits the application of this drug for treatment and prophylaxis of SSIs. Thus, rapid identification of metronidazole-resistant B. fragilis is essential to restrict inappropriate, superfluous administration. In spite of various metronidazole resistance mechanisms other than that depending on the nim gene, detection of nim by PCR is unsuitable for identifying resistant isolates. Therefore, phenotypic methods are better to screen for and identify metronidazole-resistant B. fragilis.
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Affiliation(s)
- Mohammad Taghi Akhi
- Research Center of Infectious and Tropical Disease, Tabriz University of Medical Sciences, Tabriz, Iran.,Department of Bacteriology and Virology, School of Medicine, Tabriz University of Medical Sciences, Iran
| | - Reza Ghotaslou
- Department of Bacteriology and Virology, School of Medicine, Tabriz University of Medical Sciences, Iran
| | - Naser Alizadeh
- Department of Bacteriology and Virology, School of Medicine, Tabriz University of Medical Sciences, Iran
| | - Mina Yekani
- Department of Bacteriology and Virology, School of Medicine, Tabriz University of Medical Sciences, Iran
| | - Samad Beheshtirouy
- Cardiothoracic Department, Tabriz University of Medical Sciences, Tabriz, Iran
| | | | - Tahereh Pirzadeh
- Department of Bacteriology and Virology, School of Medicine, Tabriz University of Medical Sciences, Iran
| | - Mohammad Yousef Memar
- Research Center of Infectious and Tropical Disease, Tabriz University of Medical Sciences, Tabriz, Iran.,Department of Bacteriology and Virology, School of Medicine, Tabriz University of Medical Sciences, Iran
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Rocha ER, Krykunivsky AS. Anaerobic utilization of Fe(III)-xenosiderophores among Bacteroides species and the distinct assimilation of Fe(III)-ferrichrome by Bacteroides fragilis within the genus. Microbiologyopen 2017; 6:e00479. [PMID: 28397401 PMCID: PMC5552952 DOI: 10.1002/mbo3.479] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2017] [Revised: 02/24/2017] [Accepted: 03/07/2017] [Indexed: 01/01/2023] Open
Abstract
In this study, we show that Bacteroides species utilize Fe(III)-xenosiderophores as the only source of exogenous iron to support growth under iron-limiting conditions in vitro anaerobically. Bacteroides fragilis was the only species able to utilize Fe(III)-ferrichrome while Bacteroides vulgatus ATCC 8482 and Bacteroides thetaiotaomicron VPI 5482 were able to utilize both Fe(III)-enterobactin and Fe(III)-salmochelin S4 as the only source of iron in a dose-dependent manner. We have investigated the way B. fragilis assimilates Fe(III)-ferrichrome as initial model to understand the utilization of xenosiderophores in anaerobes. B. fragilis contains two outer membrane TonB-dependent transporters (TBDTs), FchA1 and FchA2, which are homologues to Escherichia coli ferrichrome transporter FhuA. The disruption of fchA1 gene had only partial growth defect on Fe(III)-ferrichrome while the fchA2 mutant had no growth defect compared to the parent strain. The genetic complementation of fchA1 gene restored growth to parent strain levels indicating that it plays a role in Fe(III)-ferrichrome assimilation though we cannot rule out some functional overlap in transport systems as B. fragilis contains abundant TBDTs whose functions are yet not understood. However, the growth of B. fragilis on Fe(III)-ferrichrome was abolished in a feoAB mutant indicating that Fe(III)-ferrichrome transported into the periplasmic space was reduced in the periplasm releasing ferrous iron prior to transport through the FeoAB transport system. Moreover, the release of iron from the ferrichrome may be linked to the thiol redox system as the trxB deletion mutant was also unable to grow in the presence of Fe(III)-ferrichrome. The genetic complementation of feoAB and trxB mutants completely restored growth on Fe(III)-ferrichrome. Taken together, these findings show that Bacteroides species have developed mechanisms to utilize ferric iron bound to xenosiderophores under anaerobic growth conditions though the regulation and role in the biology of Bacteroides in the anaerobic intestinal environment remain to be understood.
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Affiliation(s)
- Edson R. Rocha
- Department of Microbiology and ImmunologyBrody School of MedicineEast Carolina UniversityGreenvilleNC
| | - Anna S. Krykunivsky
- Department of Microbiology and ImmunologyBrody School of MedicineEast Carolina UniversityGreenvilleNC
- Intern from the Undergraduate Research Internship Placement ProgramUniversity of the West of England (UWE)BristolUK
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30
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Bacteria-Bacteriophage Coevolution in the Human Gut: Implications for Microbial Diversity and Functionality. Trends Microbiol 2017; 25:614-623. [PMID: 28342597 DOI: 10.1016/j.tim.2017.02.012] [Citation(s) in RCA: 71] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2016] [Revised: 02/15/2017] [Accepted: 02/24/2017] [Indexed: 02/08/2023]
Abstract
Antagonistic coevolution (AC) between bacteria and bacteriophages plays a key role in driving and maintaining microbial diversity. Consequently, AC is predicted to affect all levels of biological organisation, from the individual to ecosystem scales. Nonetheless, we know nothing about bacteria-bacteriophage AC in perhaps the most important and clinically relevant microbial ecosystem known to humankind - the human gut microbiome. In this opinion piece I review current research on bacteria-phage AC in in vitro and natural populations of microbes. I then examine the evidence and discuss the potential role of AC in driving observed patterns of intra- and interindividual variation in the gut microbiome together with detailing the potential functional consequences of such AC-driven microbial variation for human health and disease.
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31
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Abstract
A 2-year longitudinal microbiome study of 22 patients who underwent colectomy with an ileal pouch anal anastomosis detected significant increases in distinct populations of Bacteroides during 9 of 11 patient visits that coincided with inflammation (pouchitis). Oligotyping and metagenomic short-read annotation identified Bacteroides populations that occurred in early samples, bloomed during inflammation, and reappeared after antibiotic treatment. Targeted cultivation of Bacteroides isolates from the same individual at multiple time points and from several patients detected subtle genomic changes, including the identification of rapidly evolving genomic elements that differentiate isogenic strains of Bacteroides fragilis from the mucosa versus lumen. Each patient harbored Bacteroides spp. that are closely related to commonly occurring clinical isolates, including Bacteroides ovatus, B. thetaiotaomicron, B. vulgatus, and B. fragilis, which contained unique loci in different patients for synthesis of capsular polysaccharides. The presence of unique Bacteroides capsular polysaccharide loci within different hosts and between the lumen and mucosa may represent adaptations to stimulate, suppress, and evade host-specific immune responses at different microsites of the ileal pouch. This longitudinal study provides an opportunity to describe shifts in the microbiomes of individual patients who suffer from ulcerative colitis (UC) prior to and following inflammation. Pouchitis serves as a model for UC with a predictable incidence of disease onset and enables prospective longitudinal investigations of UC etiology prior to inflammation. Because of insufficient criteria for predicting which patients will develop UC or pouchitis, the interpretation of cross-sectional study designs suffers from lack of information about the microbiome structure and host gene expression patterns that directly correlate with the onset of disease. Our unique longitudinal study design allows each patient to serve as their own control, providing information about the state of the microbiome and host prior to and during the course of disease. Of significance to the broader community, this study identifies microbial strains that may have genetic elements that trigger the onset of disease in susceptible hosts.
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32
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van Houte S, Buckling A, Westra ER. Evolutionary Ecology of Prokaryotic Immune Mechanisms. Microbiol Mol Biol Rev 2016; 80:745-63. [PMID: 27412881 PMCID: PMC4981670 DOI: 10.1128/mmbr.00011-16] [Citation(s) in RCA: 170] [Impact Index Per Article: 18.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Bacteria have a range of distinct immune strategies that provide protection against bacteriophage (phage) infections. While much has been learned about the mechanism of action of these defense strategies, it is less clear why such diversity in defense strategies has evolved. In this review, we discuss the short- and long-term costs and benefits of the different resistance strategies and, hence, the ecological conditions that are likely to favor the different strategies alone and in combination. Finally, we discuss some of the broader consequences, beyond resistance to phage and other genetic elements, resulting from the operation of different immune strategies.
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Affiliation(s)
- Stineke van Houte
- ESI and CEC, Department of Biosciences, University of Exeter, Exeter, United Kingdom
| | - Angus Buckling
- ESI and CEC, Department of Biosciences, University of Exeter, Exeter, United Kingdom
| | - Edze R Westra
- ESI and CEC, Department of Biosciences, University of Exeter, Exeter, United Kingdom
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33
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The interplay between microbiota and inflammation: lessons from peritonitis and sepsis. Clin Transl Immunology 2016; 5:e90. [PMID: 27525063 PMCID: PMC4973320 DOI: 10.1038/cti.2016.32] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2016] [Revised: 04/13/2016] [Accepted: 04/14/2016] [Indexed: 12/22/2022] Open
Abstract
Mammals harbor a complex gut-associated microbiota, comprising bacteria that provide immunological, metabolic and neurological benefits to the host, and contribute to their well-being. However, dysregulation of the microbiota composition, known as dysbiosis, along with the associated mucosal immune response have a key role in the pathogenesis of many inflammatory diseases, including inflammatory bowel diseases (IBDs), type 1 and type 2 diabetes, asthma, multiple sclerosis, among others. In addition, outside the gut lumen, bacteria from microbiota are the causative agent of peritoneal inflammation, abdominal sepsis and systemic sepsis. Critical care interventions during sepsis by antibiotics induce dysbiosis and present acute and long-term poor prognosis. In this review, we discuss immunomodulatory effects of the microbial molecules and products, highlighting the role of Bacteroides fragilis, a human commensal with ambiguous interactions with the host. Moreover, we also address the impact of antibiotic treatment in sepsis outcome and discuss new insights for microbiota modulation.
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Grylak-Mielnicka A, Bidnenko V, Bardowski J, Bidnenko E. Transcription termination factor Rho: a hub linking diverse physiological processes in bacteria. Microbiology (Reading) 2016; 162:433-447. [DOI: 10.1099/mic.0.000244] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Affiliation(s)
- Aleksandra Grylak-Mielnicka
- Micalis Institute, INRA, AgroParisTech, Université Paris-Saclay, 78350 Jouy-en-Josas, France
- Institute of Biochemistry and Biophysics PAS, 02-106 Warsaw, Poland
| | - Vladimir Bidnenko
- Micalis Institute, INRA, AgroParisTech, Université Paris-Saclay, 78350 Jouy-en-Josas, France
| | - Jacek Bardowski
- Institute of Biochemistry and Biophysics PAS, 02-106 Warsaw, Poland
| | - Elena Bidnenko
- Micalis Institute, INRA, AgroParisTech, Université Paris-Saclay, 78350 Jouy-en-Josas, France
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Kinjo Y, Saitoh S, Tokuda G. An Efficient Strategy Developed for Next-Generation Sequencing of Endosymbiont Genomes Performed Using Crude DNA Isolated from Host Tissues: A Case Study of Blattabacterium cuenoti Inhabiting the Fat Bodies of Cockroaches. Microbes Environ 2015; 30:208-20. [PMID: 26156552 PMCID: PMC4567559 DOI: 10.1264/jsme2.me14153] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Whole-genome sequencing has emerged as one of the most effective means to elucidate the biological roles and molecular features of obligate intracellular symbionts (endosymbionts). However, the de novo assembly of an endosymbiont genome remains a challenge when host and/or mitochondrial DNA sequences are present in a dataset and hinder the assembly of the genome. By focusing on the traits of genome evolution in endosymbionts, we herein developed and investigated a genome-assembly strategy that consisted of two consecutive procedures: the selection of endosymbiont contigs from an output obtained from a de novo assembly performed using a TBLASTX search against a reference genome, named TBLASTX Contig Selection and Filtering (TCSF), and the iterative reassembling of the genome from reads mapped on the selected contigs, named Iterative Mapping and ReAssembling (IMRA), to merge the contigs. In order to validate this approach, we sequenced two strains of the cockroach endosymbiont Blattabacterium cuenoti and applied this strategy to the datasets. TCSF was determined to be highly accurate and sensitive in contig selection even when the genome of a distantly related free-living bacterium was used as a reference genome. Furthermore, the use of IMRA markedly improved sequence assemblies: the genomic sequence of an endosymbiont was almost completed from a dataset containing only 3% of the sequences of the endosymbiont’s genome. The efficiency of our strategy may facilitate further studies on endosymbionts.
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Affiliation(s)
- Yukihiro Kinjo
- Tropical Biosphere Research Center, University of the Ryukyus
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Complete Genome Sequence of an Enterotoxigenic Bacteroides fragilis Clinical Isolate. GENOME ANNOUNCEMENTS 2015; 3:3/3/e00450-15. [PMID: 25953165 PMCID: PMC4424316 DOI: 10.1128/genomea.00450-15] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Here we present the complete genome sequence of Bacteroides fragilis isolate BOB25. It is an enterotoxigenic isolate that was obtained from a stool sample of a patient with dysbiosis.
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Ngo A, Fong KT, Cox DL, Chen X, Fisher AJ. Structures of Bacteroides fragilis uridine 5'-diphosphate-N-acetylglucosamine (UDP-GlcNAc) acyltransferase (BfLpxA). ACTA CRYSTALLOGRAPHICA. SECTION D, BIOLOGICAL CRYSTALLOGRAPHY 2015; 71:1068-76. [PMID: 25945572 PMCID: PMC4427197 DOI: 10.1107/s1399004715003326] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/10/2015] [Accepted: 02/16/2015] [Indexed: 11/11/2022]
Abstract
Uridine 5'-diphosphate-N-acetylglucosamine (UDP-GlcNAc) acyltransferase (LpxA) catalyzes a reversible reaction for adding an O-acyl group to the GlcNAc in UDP-GlcNAc in the first step of lipid A biosynthesis. Lipid A constitutes a major component of lipopolysaccharides, also referred to as endotoxins, which form the outer monolayer of the outer membrane of Gram-negative bacteria. Ligand-free and UDP-GlcNAc-bound crystal structures of LpxA from Bacteroides fragilis NCTC 9343, the most common pathogenic bacteria found in abdominal abscesses, have been determined and are presented here. The enzyme crystallizes in a cubic space group, with the crystallographic threefold axis generating the biological functional homotrimer and with each monomer forming a nine-rung left-handed β-helical (LβH) fold in the N-terminus followed by an α-helical motif in the C-terminus. The structure is highly similar to LpxA from other organisms. Yet, despite sharing a similar LβH structure with LpxAs from Escherichia coli and others, previously unseen calcium ions are observed on the threefold axis in B. fragilis LpxA to help stabilize the trimeric assembly.
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Affiliation(s)
- Alice Ngo
- Department of Chemistry, University of California, One Shields Avenue, Davis, CA 95616, USA
| | - Kai T. Fong
- Department of Chemistry, University of California, One Shields Avenue, Davis, CA 95616, USA
| | - Daniel L. Cox
- Department of Physics, University of California, One Shields Avenue, Davis, CA 95616, USA
| | - Xi Chen
- Department of Chemistry, University of California, One Shields Avenue, Davis, CA 95616, USA
| | - Andrew J. Fisher
- Department of Chemistry, University of California, One Shields Avenue, Davis, CA 95616, USA
- Department of Molecular and Cellular Biology, University of California, One Shields Avenue, Davis, CA 95616, USA
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Veeranagouda Y, Husain F, Tenorio EL, Wexler HM. Identification of genes required for the survival of B. fragilis using massive parallel sequencing of a saturated transposon mutant library. BMC Genomics 2014; 15:429. [PMID: 24899126 PMCID: PMC4072883 DOI: 10.1186/1471-2164-15-429] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2014] [Accepted: 05/27/2014] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Bacteroides fragilis is a Gram-negative anaerobe that is normally a human gut commensal; it comprises a small percentage of the gut Bacteroides but is the most frequently isolated Bacteroides from human infections. Identification of the essential genes necessary for the survival of B. fragilis provides novel information which can be exploited for the treatment of bacterial infections. RESULTS Massive parallel sequencing of saturated transposon mutant libraries (two mutant pools of approximately 50,000 mutants each) was used to determine the essential genes for the growth of B. fragilis 638R on nutrient rich medium. Among the 4326 protein coding genes, 550 genes (12.7%) were found to be essential for the survival of B. fragilis 638R. Of the 550 essential genes, only 367 genes were assigned to a Cluster of Orthologous Genes, and about 290 genes had Kyoto Encyclopedia of Genes and Genomes orthologous members. Interestingly, genes with hypothetical functions accounted for 41.3% of essential genes (227 genes), indicating that the functions of a significant percentage of the genes used by B. fragilis 638R are still unknown. Global transcriptome analysis using RNA-Seq indicated that most of the essential genes (92%) are, in fact, transcribed in B. fragilis 638R including most of those coding for hypothetical proteins. Three hundred fifty of the 550 essential genes of B. fragilis 638R are present in Database of Essential Genes. 10.02 and 31% of those are genes included as essential genes for nine species (including Gram-positive pathogenic bacteria). CONCLUSIONS The essential gene data described in this investigation provides a valuable resource to study gene function and pathways involved in B. fragilis survival. Thorough examination of the B. fragilis-specific essential genes and genes that are shared between divergent organisms opens new research avenues that will lead to enhanced understanding of survival strategies used by bacteria in different microniches and under different stress situations.
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Galvão BPGV, Weber BW, Rafudeen MS, Ferreira EO, Patrick S, Abratt VR. Identification of a collagen type I adhesin of Bacteroides fragilis. PLoS One 2014; 9:e91141. [PMID: 24618940 PMCID: PMC3949742 DOI: 10.1371/journal.pone.0091141] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2013] [Accepted: 02/07/2014] [Indexed: 01/26/2023] Open
Abstract
Bacteroides fragilis is an opportunistic pathogen which can cause life threatening infections in humans and animals. The ability to adhere to components of the extracellular matrix, including collagen, is related to bacterial host colonisation. Collagen Far Western analysis of the B. fragilis outer membrane protein (OMP) fraction revealed the presence two collagen adhesin bands of ∼ 31 and ∼ 34 kDa. The collagen adhesins in the OMP fraction were separated and isolated by two-dimensional SDS-PAGE and also purified by collagen affinity chromatography. The collagen binding proteins isolated by both these independent methods were subjected to tandem mass spectroscopy for peptide identification and matched to a single hypothetical protein encoded by B. fragilis NCTC 9343 (BF0586), conserved in YCH46 (BF0662) and 638R (BF0633) and which is designated in this study as cbp1 (collagen binding protein). Functionality of the protein was confirmed by targeted insertional mutagenesis of the cbp1 gene in B. fragilis GSH18 which resulted in the specific loss of both the ∼ 31 kDa and the ∼ 34 kDa adhesin bands. Purified his-tagged Cbp1, expressed in a B. fragilis wild-type and a glycosylation deficient mutant, confirmed that the cbp1 gene encoded the observed collagen adhesin, and showed that the 34 kDa band represents a glycosylated version of the ∼ 31 kDa protein. Glycosylation did not appear to be required for binding collagen. This study is the first to report the presence of collagen type I adhesin proteins in B. fragilis and to functionally identify a gene encoding a collagen binding protein.
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Affiliation(s)
| | - Brandon W. Weber
- Structural Biology Research Unit, Division of Medical Biochemistry, Department of Clinical Laboratory Sciences, University of Cape Town, Observatory, Western Cape, South Africa
| | - Mohamed S. Rafudeen
- Department of Molecular and Cell Biology, University of Cape Town, Cape Town, RSA
| | - Eliane O. Ferreira
- Departamento de Microbiologia Médica, UFRJ, Instituto de Microbiologia Prof. Paulo de Góes, Ilha do Fundão, Rio de Janeiro, Brazil
- Universidade Federal do Rio de Janeiro - Polo Xerém, Duque de Caxias, Rio de Janeiro, Brazil
| | - Sheila Patrick
- Centre for Infection and Immunity, School of Medicine, Dentistry and Biomedical Sciences, Queen's University Belfast, Belfast, United Kingdom
| | - Valerie R. Abratt
- Department of Molecular and Cell Biology, University of Cape Town, Cape Town, RSA
- * E-mail:
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40
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Insights into the ropy phenotype of the exopolysaccharide-producing strain Bifidobacterium animalis subsp. lactis A1dOxR. Appl Environ Microbiol 2013; 79:3870-4. [PMID: 23584772 DOI: 10.1128/aem.00633-13] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The proteome of the ropy strain Bifidobacterium animalis subsp. lactis A1dOxR, compared to that of its nonropy isogenic strain, showed an overproduction of a protein involved in rhamnose biosynthesis. Results were confirmed by gene expression analysis, and this fact agreed with the high rhamnose content of the ropy exopolysaccharide.
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41
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Sóki J. Extended role for insertion sequence elements in the antibiotic resistance of Bacteroides. World J Clin Infect Dis 2013; 3:1-12. [DOI: 10.5495/wjcid.v3.i1.1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/13/2012] [Revised: 12/04/2012] [Accepted: 12/17/2012] [Indexed: 02/06/2023] Open
Abstract
The Bacteroides species are important micro-organisms, both in the normal physiology of the intestines and as frequent opportunistic anaerobic pathogens, with a deeply-rooted phylogenetic origin endowing them with some interesting biological features. Their prevalence in anaerobic clinical specimens is around 60%-80%, and they display the most numerous and highest rates of antibiotic resistance among all pathogenic anaerobes. In these antibiotic resistance mechanisms there is a noteworthy role for the insertion sequence (IS) elements, which are usually regarded as representatives of ‘selfish’ genes; the IS elements of Bacteroides are usually capable of up-regulating the antibiotic resistance genes. These include the cepA (penicillin and cephalosporin), cfxA (cephamycin), cfiA (carbapenem), nim (metronidazole) and ermF (clindamycin) resistance genes. This is achieved by outward-oriented promoter sequences on the ISs. Although some representatives are well characterized, e.g., the resistance gene-IS element pairs in certain resistant strains, open questions remain in this field concerning a better understanding of the molecular biology of the antibiotic resistance mechanisms of Bacteroides, which will have clinical implications.
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42
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Wakimoto S, Nakayama-Imaohji H, Ichimura M, Morita H, Hirakawa H, Hayashi T, Yasutomo K, Kuwahara T. PhoB regulates the survival of Bacteroides fragilis in peritoneal abscesses. PLoS One 2013; 8:e53829. [PMID: 23342014 PMCID: PMC3547664 DOI: 10.1371/journal.pone.0053829] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2012] [Accepted: 12/03/2012] [Indexed: 12/22/2022] Open
Abstract
In response to phosphate limitation, bacteria employ the Pho regulon, a specific regulatory network for phosphate acquisition. The two-component signal transduction system of PhoRB plays a crucial role in the induction of Pho regulon genes, leading to the adaptation to phosphate starvation. Herein, we identified the PhoRB system in Bacteroides fragilis, a commensal gut bacterium, and evaluated its role in gut colonization and survival in peritoneal abscesses. BF1575 and BF1576 encoded PhoR (sensor histidine kinase) and PhoB (response regulator) in the sequenced B. fragilis strain YCH46, respectively. Transcriptome analysis revealed that deletion of phoB affected the expression of 585 genes (more than 4-fold change) in B. fragilis, which included genes for stress response (chaperons and heat shock proteins), virulence (capsular polysaccharide biosynthesis) and phosphate metabolism. Deletion of phoB reduced the ability of the bacterium to persist in peritoneal abscesses induced by an intra-abdominal challenge of B. fragilis. Furthermore, PhoB was necessary for survival of this anaerobe in peritoneal abscesses but not for in vitro growth in rich media or in intestinal colonization. These results indicate that PhoB plays an important role in the survival of B. fragilis under stressful extraintestinal conditions.
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Affiliation(s)
- Shin Wakimoto
- Department of Immunology and Parasitology, Institute of Health Biosciences, The University of Tokushima Graduate School, Tokushima, Japan
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Letzel AC, Pidot SJ, Hertweck C. A genomic approach to the cryptic secondary metabolome of the anaerobic world. Nat Prod Rep 2012; 30:392-428. [PMID: 23263685 DOI: 10.1039/c2np20103h] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
A total of 211 complete and published genomes from anaerobic bacteria are analysed for the presence of secondary metabolite biosynthesis gene clusters, in particular those tentatively coding for polyketide synthases (PKS) and non-ribosomal peptide synthetases (NRPS). We investigate the distribution of these gene clusters according to bacterial phylogeny and, if known, correlate these to the type of metabolic pathways they encode. The potential of anaerobes as secondary metabolite producers is highlighted.
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Affiliation(s)
- Anne-Catrin Letzel
- Leibniz Institute for Natural Product Research and Infection Biology HKI, Beutenbergstr. 11a, Jena, 07745, Germany
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Huang X, Zhao Y, Dai Y, Wu G, Shao Z, Zeng Q, liu Z. Cloning and biochemical characterization of a glucosidase from a marine bacterium Aeromonas sp. HC11e-3. World J Microbiol Biotechnol 2012; 28:3337-44. [DOI: 10.1007/s11274-012-1145-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2012] [Accepted: 08/02/2012] [Indexed: 11/30/2022]
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Discerning the role of Bacteroides fragilis in celiac disease pathogenesis. Appl Environ Microbiol 2012; 78:6507-15. [PMID: 22773639 DOI: 10.1128/aem.00563-12] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Celiac disease (CD) is associated with intestinal dysbiosis, which can theoretically lead to dysfunctions in host-microbe interactions and contribute to the disease. In the present study, possible differences in Bacteroides spp. and their pathogenic features between CD patients and controls were investigated. Bacteroides clones (n = 274) were isolated, identified, and screened for the presence of the virulence genes (bft and mpII) coding for metalloproteases. The proteolytic activity of selected Bacteroides fragilis strains was evaluated by zymography and, after gastrointestinal digestion of gliadin, by high-pressure liquid chromatography/electrospray ionization/tandem mass spectrometry. The effects of B. fragilis strains on Caco-2 cell culture permeability and inflammatory response to digested gliadin were determined. B. fragilis was more frequently identified in CD patients than in healthy controls, in contrast to Bacteroides ovatus. B. fragilis clones carrying virulence genes coding for metalloproteases were more abundant in CD patients than in controls. B. fragilis strains, representing the isolated clones and carrying metalloprotease genes, showed gelatinase activity and exerted the strongest adverse effects on the integrity of the Caco-2 cell monolayer. All B. fragilis strains also showed gliadin-hydrolyzing activity, and some of them generated immunogenic peptides that preserved or increased inflammatory cytokine production (tumor necrosis factor alpha) and showed increased ability to permeate through Caco-2 cell cultures. These findings suggest that increased abundance of B. fragilis strains with metalloprotease activities could play a role in CD pathogenesis, although further in vivo studies are required to support this hypothesis.
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Veeranagouda Y, Husain F, Wexler HM. Transposon mutagenesis of the anaerobic commensal, Bacteroides fragilis, using the EZ::TN5 transposome. FEMS Microbiol Lett 2012; 333:94-100. [PMID: 22639975 DOI: 10.1111/j.1574-6968.2012.02602.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2012] [Revised: 04/24/2012] [Accepted: 05/23/2012] [Indexed: 01/24/2023] Open
Abstract
Genetic analysis of Bacteroides fragilis (BF) is hindered because of the lack of efficient transposon mutagenesis methods. Here, we describe a simple method for transposon mutagenesis using EZ::TN5, a commercially available system that we optimized for use in BF638R. The modified EZ::TN5 transposon contains an Escherichia coli conditional origin of replication, a kanamycin resistance gene for E. coli, an erythromycin resistance gene for BF , and 19 basepair transposase recognition sequences on either ends. Electroporation of the transposome (transposon-transposase complex) into BF638R yielded 3.2 ± 0.35 × 10(3) CFU μg(-1) of transposon DNA. Modification of the transposon by the BF638R restriction/modification system increased transposition efficiency sixfold. Electroporation of the EZ::TN5 transposome results in a single-copy insertion of the transposon evenly distributed across the genome of BF638R and can be used to construct a BF638R transposon library. The transposon was also effective in mutating a BF clinical isolate and a strain of the related species, Bacteroides thetaiotaomicron. The EZ::TN5-based mutagenesis described here is more efficient than other transposon mutagenesis approaches previously reported for BF.
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Affiliation(s)
- Yaligara Veeranagouda
- GLAVAHCS, Los Angeles, CA, USA; UCLA School of Medicine, Los Angeles, CA 90073, USA.
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47
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In celebration of Sydney M. Finegold, M.D.: Bacteroides fragilis in the colon: The good & the bad. Anaerobe 2012; 18:192-6. [DOI: 10.1016/j.anaerobe.2012.01.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2011] [Revised: 01/16/2012] [Accepted: 01/18/2012] [Indexed: 11/19/2022]
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48
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Yother J. Capsules ofStreptococcus pneumoniaeand Other Bacteria: Paradigms for Polysaccharide Biosynthesis and Regulation. Annu Rev Microbiol 2011; 65:563-81. [DOI: 10.1146/annurev.micro.62.081307.162944] [Citation(s) in RCA: 222] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Janet Yother
- Department of Microbiology, University of Alabama, Birmingham, Alabama 35294-2170;
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Mother-to-child transmission of and multiple-strain colonization by Bacteroides fragilis in a cohort of mothers and their children. Appl Environ Microbiol 2011; 77:8318-24. [PMID: 21965394 DOI: 10.1128/aem.05293-11] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Bacteroides fragilis represents an early infant colonizer with important host interactions. Our knowledge about the diversity, transmission, and persistence of this bacterium, however, is limited. Here, we addressed these questions using a combination of multilocus sequence typing (MLST) and variable-number tandem repeat (VNTR) sequence analyses. We used both culture-dependent and -independent typing. We genotyped B. fragilis in fecal samples from a cohort of 93 mothers and their children, with samples taken from the mothers and from the children at the ages 1 to 10 days, 4 months, 1 year, and 2 years. By MLST we found two main B. fragilis groups, which we denoted clades A and B. Direct typing of stool samples using the icd gene revealed seven sequence types, five within clade A and two within clade B. A single clade A sequence type, however, represented 79% of all the sequences. This sequence type was further subtyped using VNTR. VNTR subtyping revealed 16 different VNTR types. Based on the distribution patterns of these, we show mother-to-child transmission and multiple-strain colonization. We argue that negative host selection promotes the coexistence of multiple strains. The significance of our findings is that we have started unraveling the transmission and persistence patterns of one of the most important human gut colonizers.
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50
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Patrick S, Jobling KL, O'Connor D, Thacker Z, Dryden DTF, Blakely GW. A unique homologue of the eukaryotic protein-modifier ubiquitin present in the bacterium Bacteroides fragilis, a predominant resident of the human gastrointestinal tract. MICROBIOLOGY-SGM 2011; 157:3071-3078. [PMID: 21885481 PMCID: PMC3352274 DOI: 10.1099/mic.0.049940-0] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
In the complete genome sequences of Bacteroides fragilis NCTC9343 and 638R, we have discovered a gene, ubb, the product of which has 63 % identity to human ubiquitin and cross-reacts with antibodies raised against bovine ubiquitin. The sequence of ubb is closest in identity (76 %) to the ubiquitin gene from a migratory grasshopper entomopoxvirus, suggesting acquisition by inter-kingdom horizontal gene transfer. We have screened clinical isolates of B. fragilis from diverse geographical regions and found that ubb is present in some, but not all, strains. The gene is transcribed and the mRNA is translated in B. fragilis, but deletion of ubb did not have a detrimental effect on growth. BfUbb has a predicted signal sequence; both full-length and processed forms were detected in whole-cell extracts, while the processed form was found in concentrated culture supernatants. Purified recombinant BfUbb inhibited in vitro ubiquitination and was able to covalently bind the human E1 activating enzyme, suggesting it could act as a suicide substrate in vivo. B. fragilis is one of the predominant members of the normal human gastrointestinal microbiota with estimates of up to >1011 cells per g faeces by culture. These data indicate that the gastro-intestinal tract of some individuals could contain a significant amount of aberrant ubiquitin with the potential to inappropriately activate the host immune system and/or interfere with eukaryotic ubiquitin activity. This discovery could have profound implications in relation to our understanding of human diseases such as inflammatory bowel and autoimmune diseases.
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Affiliation(s)
- Sheila Patrick
- Centre for Infection and Immunity, School of Medicine, Dentistry and Biomedical Sciences, Queen's University Belfast, Medical Biology Centre, Belfast BT9 7BL, UK
| | - Kelly L Jobling
- Institute of Cell Biology, University of Edinburgh, Darwin Building, The Kings Buildings, Edinburgh EH9 3JR, UK
| | - Danny O'Connor
- Centre for Infection and Immunity, School of Medicine, Dentistry and Biomedical Sciences, Queen's University Belfast, Medical Biology Centre, Belfast BT9 7BL, UK
| | - Zubin Thacker
- Institute of Cell Biology, University of Edinburgh, Darwin Building, The Kings Buildings, Edinburgh EH9 3JR, UK
| | - David T F Dryden
- EaStChem School of Chemistry, University of Edinburgh, The Kings Buildings, Edinburgh EH9 3JJ, UK
| | - Garry W Blakely
- Institute of Cell Biology, University of Edinburgh, Darwin Building, The Kings Buildings, Edinburgh EH9 3JR, UK
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