The host restricted pathogens are competently dependent on their respective host for nutritional requirements. The bacterial metabolic pathways are surprisingly varied and remarkably flexible that in turn help them to successfully overcome competition and colonise their host. The metabolic adaptation plays pivotal role in bacterial pathogenesis. The understanding of host-pathogen metabolic crosstalk needs to be prioritized to decipher host-pathogen interactions. The review focuses on various aspects of host pathogen interactions that majorly involves adaptation of bacterial metabolism to counteract immune mechanisms by rectifying metabolic cues that provides pathogen the idea of different anatomical sites and the local physiology of the host. The key set of metabolites that are recognized as centre of competition between host and its pathogens are also briefly discussed. The factors that control the timely expression of virulence of bacterial pathogens is poorly understood. The perspective presented herein will facilitate us with a broader view of molecular mechanisms that modulates the expression of virulence factors in bacterial pathogens. The knowledge of crosslinked metabolic pathways of bacteria and their host will serve to develop novel potential therapeutics.

Anthropogenic activities like heavy metal pollution exert the most devastating effect on agriculture. Siderophores are small peptides capable to chelate iron and different heavy metals; thereby reduce metal toxicity. However, very little information is available about their physiology (siderophore types, effect of temperature, pH, toxic metals), and especially of their gene expression patterns. Here, we have carried out a detailed study on siderophore production dynamics along with their gene expression pattern in Enterobacter sp. DRP3. DRP3 was able to produce two different types of siderophores hydroxamate type (19.81 µg ml-1) during early stages and catecholate type (59.52 µg ml-1) later stages of its growth, especially at pH-6.8. DRP3 was able to produce similar concentrations of siderophores even under high lead concentrations. Further whole genome analysis has revealed the presence of enterobactin and aerobactin gene clusters. Quantitative real-time PCR observed a 5.02-fold and 1.90-fold overexpression of the enterobactin biosynthesis genes entC and entF, respectively, and a 3.12-fold upregulation of the aerobactin biosynthesis gene iucC in the absence of exogenously added Fe3+ by DRP3. Our study also highlighted that following root colonization DRP3 is excellent in mitigating Pb(II) stress in rice seedlings while promoting iron content and reducing lead content in plant tissue.

Siderophores are iron chelators secreted by microorganisms to scavenge iron from the environment. Natural siderophores have gained remarkable importance because their conjugates can be applied as antibiotics and diagnostic imaging agents. By utilizing the iron uptake system of microorganisms, functional molecules such as antibiotics or imaging agents can be delivered into cells. Notably, artificial siderophores have also been developed to increase stability and broaden metal chelating diversity. Various strategies, including backbone fine-tuning, artificial chelation moieties, and direct metal swapping, can be employed. Therefore, artificial siderophores can bind biorelated metals or radioactive isotopes, expanding their biological and medical applications. The aim of this review is to introduce recent advances in natural and artificial siderophore applications and highlight future challenges in this area of research.

Antibiotic resistance presents an enormous threat to human well-being due to the overconsumption and misuse of these essential drugs in recent years. A novel and intriguing path to overcoming the ever-pressing problem appears in the "Trojan horse" strategy exploiting bacteria's internalization systems and their exceptional capability to scavenge metal ions, iron in particular, from the surrounding media when evading the host organism. A promising candidate in this field is the abiogenic cation gallium─a ferric mimetic species, known to exert diverse effects, with its well-pronounced antibacterial activity attracting the attention of scientists in the past decade. In the study presented herewith, the computational chemistry methods, based on Density Functional Theory (DFT), are utilized in order to differentiate those outer factors contributing to gallium's ability to substitute the native ferric ion in the active site of the enzyme catalase. The characteristics of the surrounding media such as pH and solvent exposure, the composition of the protein shell, the nature of the metal, and different substrate molecules have been taken into account. The obtained results are interpreted in light of the experimentally reported observations and aim to contribute to deciphering this aspect of gallium's mechanism of antibacterial activity.

To study the impact of a laparoscopic niche resection on vaginal microbiota in relation to pregnancy rate.

A explorative prospective cohort study that included women with a large niche (residual myometrium ≤ 3 mm), actual wish to conceive who were scheduled for laparoscopic niche resection. Pre- and three months post-operatively, a vaginal swab was collected during the mid-luteal phase (cycle day 19 to 24). The microbiota composition was determined using 16S rDNA sequencing. Microbiota profiles were assigned to community state types (CST) based on the dominant bacterial species.

In total, 55 women completed sequential sampling. In all women, laparoscopic niche resection significantly reduced niche volume, withmean paireddifference of 1766.6 mm3 (95 % CI: 640.4 - 2892.8). CST-IV was the dominant type both pre- and post-operatively (38.2 % vs 36.4 %, respectively). In ten (18.2 %) women the dominant CST changed after surgery. Three (5.5 %) women experienced a favourable change linked to fertility, while two (3.6 %) had unfavourable change and five (9.1 %) showed neutral shift. Women with favourable change had a greater reduction in niche volume (median reduction 1067.4 mm3 (p = 0.014)). Within a year, 23 (54.8 %) women became pregnant. The highest pregnancy rate (90.0 %, n = 9) was observed in women with post-operative CST-I, while the lowest rate (38.5 %, n = 5) was seen in those with CST-III.

Laparoscopic niche resection resulted in a more than 10-fold reduction in niche volume. However, no significant changes in vaginal microbiota were observed postoperatively. Notably, women who experienced the largest reduction in niche volume also demonstrated a favourable shift in their microbiome profile, which is associated with improved fertility.Postoperatively, the highest pregnancy rate (90 %) was observed in women with Lactobacillus crispatus-dominant microbiota (p = 0.78). These results provide valuable insights into the pathophysiology of uterine niches and suggest potential therapeutic approaches for women experiencing niche-related infertility, however lager studies are needed to confirm these findings.

Community-acquired infections caused by Klebsiella pneumoniae (K. pneumoniae) have become a significant global health concern, particularly with the emergence of hypervirulent strains (hvKP). These strains are associated with severe infections, such as pyogenic liver abscesses, even in otherwise healthy individuals. Initially reported in Taiwan in the 1980s, hvKP has now spread worldwide. The pathogenicity of hvKP is attributed to an array of virulence factors that enhance its ability to colonize and evade host immune defenses. Additionally, the convergence of hypervirulence with antibiotic resistance has further complicated treatment strategies. As a member of the ESKAPE group of pathogens, K. pneumoniae exhibits high resistance to multiple antibiotics, posing a challenge for healthcare settings. This review provides a comprehensive overview of hvKP, highlighting its structural and pathogenic differences from classical K. pneumoniae strains, key virulence factors, mechanisms of antibiotic resistance, and the increasing threat of multidrug-resistant hvKP. Lastly, we discuss current treatment guidelines and emerging therapeutic strategies to combat this formidable pathogen.

Microbial metabolism and growth are tightly linked to oxygen (O2). Microbes experience fluctuating O2 levels in natural environments; however, our understanding of how cells respond to fluctuating O2 over various time scales remains limited due to challenges in observing microbial growth at single-cell resolution under controlled O2 conditions and in linking individual cell growth with the specific O2 microenvironment. We performed time-resolved microbial growth analyses at single-cell resolution under a temporally controlled O2 supply. A multilayer microfluidic device was developed, featuring a gas supply above a cultivation layer, separated by a thin membrane enabling efficient gas transfer. This platform allows microbial cultivation under constant, dynamic, and oscillating O2 conditions. Automated time-lapse microscopy and deep-learning-based image analysis provide access to spatiotemporally resolved growth data at the single-cell level. O2 switching within tens of seconds, coupled with precise microenvironment monitoring, allows us to accurately correlate cellular growth with local O2 concentrations. Growing Escherichia coli microcolonies subjected to varying O2 oscillation periods show distinct growth dynamics characterized by response and recovery phases. The comprehensive growth data and insights gained from our unique platform are a crucial step forward to systematically study cell response and adaptation to fluctuating O2 environments at single-cell resolution.

The growing threat of antibiotic resistance has made treating bacterial and fungal infections increasingly difficult. With the discovery of new antibiotics slowing down, alternative strategies are urgently needed. Siderophores, small iron-chelating molecules produced by microorganisms, play a crucial role in iron acquisition and serve as virulence factors in many pathogens. Because iron is essential for microbial survival, targeting siderophore biosynthesis and transport presents a promising approach to combating drug-resistant infections. This review explores the key genetic and biochemical mechanisms involved in siderophore production, emphasizing potential drug targets within these pathways. Three major biosynthetic routes are examined: nonribosomal peptide synthetase (NRPS)-dependent, polyketide synthase (PKS)-based, and NRPS-independent (NIS) pathways. Additionally, microbial iron uptake mechanisms and membrane-associated transport systems are discussed, providing insights into their role in sustaining pathogenic growth. Recent advances in inhibitor development have shown that blocking critical enzymes in siderophore biosynthesis can effectively impair microbial growth. By disrupting these pathways, new antimicrobial strategies can be developed, offering alternatives to traditional antibiotics and potentially reducing the risk of resistance. A deeper understanding of siderophore biosynthesis and its regulation not only reveals fundamental microbial processes but also provides a foundation for designing targeted therapeutics. Leveraging these insights could lead to novel drugs that overcome antibiotic resistance, offering new hope in the fight against persistent infections.

Human infections are greatly impacted by intestinal nematodes. These nematodes, which encompass the large roundworms, have a direct impact on human health and well-being due to their close cohabitation with the host's microorganisms. When nematodes infect a host, the microbiome composition changes, and this can impact the host's ability to control the parasites. We aimed to find out if the small intestinal roundworms produce substances that have antimicrobial properties and respond to their microbial environment, and if the immune and regulatory reactions to nematodes are altered in humans lacking gut microbes. There is no doubt that different nematodes living in the intestines can alter the balance of intestinal bacteria. Nonetheless, our knowledge about the parasite's influence on the gut microbiome remains restricted. The last two decades of study have revealed that the type of iron utilized can influence the activation of unique virulence factors. However, some roundworm proteins like P43, which makes up a large portion of the worm's excretory-secretory product, have an unknown role. This review explores how the bacterial iron regulatory network contributes to the adaptability of this opportunistic pathogen, allowing it to successfully infect nematodes in different host environments.

Shewanella are bacteria widespread in marine and brackish water environments and emergent opportunistic pathogens. Their environmental versatility depends on the ability to produce numerous iron-rich proteins, mainly multiheme c-type cytochromes. Although iron plays a vital role in the versatility of Shewanella species, very few studies exist regarding the strategies by which these bacteria scavenge iron from the environment. Siderophore-mediated iron transport is a commonly employed strategy for iron acquisition, and it was identified among Shewanella spp. over two decades ago. Shewanella species produce hydroxamate-type siderophores and iron removal from these compounds can occur in the cytoplasm via Fe(III)-siderophore reduction mediated by siderophore-interacting proteins (SIPs). The genome of Shewanella putrefaciens DSM 9451 isolated from an infected child contains representatives of the two different families of SIPs: the flavin-containing siderophore reductase (SbSIP) and the iron-sulfur cluster-containing ferric-siderophore reductase (SbFSR). Here, we report their expression, purification, and further biochemical characterization of SbSIP. The structural and functional characterization of SbSIP and comparison with the homologous SIP from Shewanella frigidimarina (SfSIP) revealed similarities between these proteins including a common binding pocket for NADH, NADPH, and siderophore substrates plus a pronounced redox-Bohr effect that ensures coupled transfer of electrons and protons in the physiological pH range. These mechanistic aspects open the door for further investigations on developing drugs that interfere with the iron metabolism of these bacteria and thereby prevent their spread.

Plant sterols (PSs) exhibit intrinsic functions such as antibacterial effects. Their effects simultaneously on both host-mediated and bacteria-mediated pathogenesis are not yet fully understood. We hypothesized that when absorptive cells, defensive cells and detoxer cells are cultured together, their convergent response to an infectious pathogen depends on the molecular mimicry between the ingested sterols and their own defensive lipids. A human triple cell co-culture model incorporating colonocytes, macrophages, and hepatocytes was established. Cocultures were stimulated with Klebsiella pneumoniae 52145 (Kp52145) in the presence of pure plant sterol (β-sitosterol, PS) for 6 h. Changes in the structural health markers of the stimulated cocultured cells and their immune response and biochemical markers of pathogenicity were determined. PS significantly inhibited the secretion of cytokines induced by Kp52145. Cell viability was higher in the Kp52145 + PS group compared to the Kp52145 alone group. PS decreased Kp52145-induced marker of pathogenicity (SOD), accompanied by reduced levels of interleukin-1β (IL-1β), interleukin-6 (IL-6), mannose binding lectin (MBL), and pentraxin 3 (PTX3) which are the mediators and enzymes associated with the inflammatory response to an infectious-inflamed milieu. PS recovered Kp52145-decreased peroxidase (POX), catalase (CAT), complement component 3 (C3), and high-density lipoprotein cholesterol (HDL-C) values. Convergence of ingested plant sterols and host eukaryotic cell-derived defensive lipids mitigates the disruptive effects of bacterial toxic effector molecules. Structural or immunological similarities (molecular mimicry) between ingested plant sterols and host defensive lipids play an important role in modulating bacterial signalling that occurs at the pathogen-host interface and in the mitigation of infection- and inflammation-driven pathological processes.

Ornithobacterium rhinotracheale (ORT) is a Gram-negative, pleomorphic rod-shaped bacterium that causes respiratory disease in the commercial poultry industry. This bacterium has been causing severe disease in chickens and turkeys since it emerged in the 1980s. In birds, increased mortality, reduced egg production, and loss in weight gain gives ORT the potential to have severe economic implications. In older birds, ORT causes more severe lesions and increases in mortality; therefore it is of particular concern in the breeder industry because infection and loss of production in breeders impact all stages of production. Despite the importance of ORT, few published studies have contributed to understanding of the diagnostics, treatment, and prevention of this disease. This review discusses the evolving landscape of ORT and summarizes an update on important issues related to ORT.

Acinetobacter baumannii is a Gram-negative opportunistic pathogen that poses a significant challenge in healthcare settings, particularly in ICUs, due to its MDR and high mortality rates, especially among critically ill coronavirus disease 2019 patients. Iron is crucial for the survival, growth and pathogenicity of A. baumannii, and the bacterium has developed multiple iron acquisition systems, including siderophore production, haem uptake and TonB-dependent transport mechanisms, to adapt to the iron-limited environment within the host. Although specific studies on A. baumannii are limited, mechanisms from other bacterial species suggest that similar iron acquisition strategies may play a key role in its virulence. Therapeutic approaches targeting these iron-dependent systems, such as the siderophore-conjugated cephalosporin cefiderocol, have shown potential in overcoming MDR A. baumannii infections. Additionally, strategies such as synthetic siderophores, TonB receptor inhibitors and iron chelators are under investigation to enhance treatment outcomes. Future research should prioritize validating these mechanisms in A. baumannii, advancing clinical trials for these therapies and exploring combination treatments to mitigate resistance and improve clinical outcomes in severely affected patients.

Hypervirulent Klebsiella pneumoniae (hvKP) is a recently emerging pathogen that causes severe community-acquired infections in immunocompetent patients, in contrast to classical K. pneumoniae, which is found in nosocomial settings. We report the case of a healthy 55-year-old woman who, following recent travel to Singapore, presented with diabetic ketoacidosis (DKA) and septic shock. She presented with fever, cough, myalgias, and confusion, imaging demonstrating bilateral cavitating pneumonia, hepatic and perinephric abscesses, and renal vein and inferior vena cava thrombosis. Whole-genome sequencing identified hvKP (ST420, K2 capsular type, rmpA, rmpA2). The patient required admission to the intensive care unit (ICU) for mechanical ventilation, broad-spectrum antibiotics, and anticoagulation, and, despite progress on a stepwise incline, irreversible cavitating lung necrosis necessitated prolonged ICU dependence (>35 days). This case is notable for hvKP's virulence, its relation to travel to endemic regions, and the impact of diabetes on susceptibility, underscoring the need for early diagnosis, targeted therapy, and scrupulous source control.

Four doses of Fe2O3 NPs suspension (10, 50, 100, and 500 mg/L) and one dose of EDTA-FeNa2 solution (10 mg/L) were foliar applied to two soybean (Glycine max) varieties (ND12 and C103) with Fusarium oxysporum. Notably, soybean disease indices were significantly reduced following foliar application of Fe2O3 NPs. At 50 mg/L Fe2O3 NPs, disease indices were reduced by 60.29 % and 43.75 % in ND12 and C103, respectively; these values were significantly better than EDTA-FeNa2, which reduced disease indices by 22.02-28.10 % compared to infected control. Furthermore, root biomass increased by 54.28 % and 42.95 %; chlorophyll a increased by 31.03 % and 43.78 %; SOD activity increased by 40.82 % and 45.59 %; and GmPAL expression increased by 16.64 and 7.23-fold with 50 mg/L Fe2O3 NPs on ND12 and C103, respectively, compared to the infected control. Importantly, the control efficiency of Fe2O3 NPs was 3-6 times higher than that of EDTA-FeNa2. Metabolomic analysis indicated that 50 mg/L Fe2O3 NPs significantly increased the metabolite content of TCA biomolecules in both soybeans; for example, citric acid increased by 102.06 % and 29.88 % compared to the infected control. The results suggest that Fe2O3 NPs mitigate root rot through multiple mechanisms, including augmentation of antioxidant enzyme activity to mitigate disease-induced oxidative stress, activation of relevant defense genes to enhance resistance, and increased levels of TCA and amino acid metabolites to provide energy for soybean response. These findings underscore the significant potential of Fe2O3 NPs in disease suppression for an environmentally friendly sustainable agriculture.

Polypharmacological approaches have significant potential for the treatment of various complex diseases, including infectious bacteria-related diseases. Actually, multitargeting agents can achieve better therapeutic effects and overcome the drawbacks of monotherapy. Although multidrug multitarget strategies have demonstrated the ability to inactivate infectious bacteria, several challenges have been pointed out. In this way, multitarget direct ligands approaches appear to be a rational and sustainable strategy to combat antibiotic resistance. By combining different pharmacophores, antibiotic hybrids stand out as a promising application in the field of bacterial infections. These new chemical entities can achieve synergistic interactions that allow to extend the spectrum of action and target multiple pathways. In addition, antibiotic hybrids can reduce the likelihood of resistance development and provide improved chemical stability. It is worth highlighting that despite the efforts of the scientific community to discover new solutions for the most complex diseases, there is a significant lack of studies on biofilm-associated infections. This review describes the different polypharmacological approaches that can be used to treat bacterial infections with a particular focus, whenever possible, on those promoted by biofilms. By exploring these innovative approaches, we aim to inspire further research and progress in the search for effective treatments for infectious bacteria-related diseases, including biofilm-related ones. SIGNIFICANCE STATEMENT: The importance of the proposed topic lies in the escalating challenge of antibiotic resistance, particularly in the context of infectious bacteria-related infections. Polypharmacological approaches, such as antibiotic hybrids, represent innovative strategies to combat bacterial infections. By targeting multiple signaling pathways, these approaches not only enhance therapeutic effect but also reduce the development of resistance while improving the drug's chemical stability. Despite the urgent need to combat bacterial infectious diseases, there is a notable research gap, in particular in biofilm-related ones. This review highlights the critical importance of exploring polypharmacological approaches with the aim of motivating further research and advances in effective treatments for infectious bacteria, including biofilm related infections.

In recent years, the research community has been interested in members of the Acinetobacter genus mainly because of their role as causative agents of nosocomial infections. However, this rich-in-species genus has been proven to play a significant role in several biotechnological processes, such as bioremediation and fermented foods production. To partially fill the lack of information on Acinetobacter's dualistic nature, in this review, based on literature data, we attempt to summarize the available information on the different roles the members of the genus play by considering their genetic constitution and metabolic properties. We analyzed reports of genetic divergence between the pathogenic and non-pathogenic species and isolates, which can be explained by their high adaptability to the different ecological niches. In turn, this adaptability could result from intrinsic genetic variability due to mechanisms of horizontal genetic transfer, as well as high mutability determined by the expression of error-prone DNA polymerases. Yet, we concluded that further studies are needed, especially whole-genome sequencing of non-pathogenic isolates, which for the moment are relatively scarce.

Stenotrophomonas maltophilia, an opportunistic pathogen, is ubiquitously distributed in the environment. In response to iron-depletion stress, S. maltophilia synthesizes the sole catecholate-type siderophore, stenobactin, for ferric iron acquisition. FepAsm, a TonB-dependent transporter (TBDT), is the sole known outer membrane receptor responsible for ferri-stenobactin uptake in S. maltophilia K279a. However, S. maltophilia KJ and its isogenic fepA mutant displayed comparable ability to utilize FeCl3 as the sole iron source for growth in iron-depleted conditions, suggesting the involvement of additional TBDT in ferri-stenobactin uptake in the KJ strain. Here, we aimed to determine additional TBDT required for ferri-stenobactin uptake and the post-TBDT ferri-stenobactin transport system in the KJ strain.

Twelve TBDTs, whose expression were significantly upregulated in 2,2'-dipyridyl-treated KJ strain, were selected as candidates for ferri-stenobactin uptake. The involvement of these selected candidates in ferri-stenobactin acquisition was investigated using deletion mutant construction and FeCl3 utilization assay. Among the 12 TBDTs tested, FepAsm, FciA, and SbaA were the TBDTs for ferri-stenobactin uptake in KJ strain. Because fciA is a member of fciTABC operon, the involvement of fciTABC operon in ferri-stenobactin uptake was also investigated. Of the fciTABC operon, fciA, fciB and fciC, but not fciT, contributed to ferri-stenobatin acquisition. SbaE is the homolog of FepD/FepG, the inner membrane transporters for ferri-enterobactin in E. coli; therefore, sbaBCDEF operon was selected as a candidate for the post-TBDT transport system of ferri-stenobactin. All proteins encoded by sbaBCDEF operon participated in ferri-stenobactin acquisition. Due to the contribution of the putative periplasmic esterase SbaB to ferri-stenobactin acquisition, FeoB, a ferrous iron inner membrane transporter, was included as a candidate and proved to be involved in ferri-stenobactin acquisition. Accordingly, contributions of feoB and sbaE to ferri-stenobactin acquisition illustrated that ferric and ferrous iron could be transported across the inner membrane via SbaE and FeoB, respectively.

FepAsm, fciABC, sbaA, sbaBCDEF, and feoB contribute to ferri-stenobatin acquisition in Stenotrophomonas maltophilia KJ.

Microorganisms acquire iron from surrounding environment through specific iron chelators known as siderophores that can be of self-origin or synthesized by neighboring microbes. The latter are termed as xenosiderophores. The acquired iron supports their growth, survival, and pathogenesis. Various microorganisms possess the ability to utilize xenosiderophores, a mechanism popularly termed as 'siderophore piracy' besides synthesizing their own siderophores. This adaptability allows microorganisms to conserve energy by reducing the load of siderogenesis. Owing to the presence of xenosiderophore transport machinery, these microbial systems can be used for targeting antibiotics-siderophore conjugates to control pathogenesis and combat antimicrobial resistance. This review outlines the significance of xenosiderophore utilization for growth, stress management and virulence. Siderogenesis and the molecular mechanism of its uptake by related organisms have been discussed vividly. It focuses on potential applications like disease diagnostics, drug delivery, and combating antibiotic resistance. In brief, this review highlights the importance of xenosiderophores projecting them beyond their role as mere iron chelators.

Pasteurella multocida infects a wide range of animals, causing hemorrhagic septicemia or infectious pneumonia. Iron is an essential nutrient for growth, colonization, and proliferation of P. multocida during infection of the host, and competition for iron ions in the host is a critical link in the pathogenesis of this pathogen. In recent years, there has been significant progress in the study of the iron uptake system of P. multocida, including its occurrence and regulatory mechanisms. In order to provide a systematic theoretical basis for the study of the molecular pathogenesis of the P. multocida iron uptake system, and generate new ideas for the investigation and development of molecular-targeted drugs and subunit vaccines against P. multocida, the mechanisms of iron uptake by transferrin receptors, heme receptors, and siderophores, and the mechanism of expression and regulation of the P. multocida iron uptake system are all described.

Iron is essential for the formation, maturation and dispersal of bacterial biofilms, playing a crucial role in the physiological and metabolic functions of bacteria as well as in the regulation of virulence. Limited availability of iron can impair the formation of robust biofilms by altering cellular motility, hydrophobicity and protein composition of the bacterial surface. In this study, the antibiofilm activity of two natural iron chelating agents, kojic acid (5-hydroxy-2-hydroxymethyl-4H-pyran-4-one) and maltol (3-hydroxy-2-methyl-4-pyrone), were investigated against Staphylococcus aureus and Pseudomonas aeruginosa. In addition, the ability of these 2-hydroxy-4-pyrone derivatives in preventing and eradicating S. aureus and P. aeruginosa biofilms through the enhancement of the efficacy of two antibiotics (tobramycin and ciprofloxacin) was explored. The iron binding capacity of the kojic acid and maltol was confirmed by their affinity for iron (III) which was found to be about 90 %, comparable to the regular chelating agent ethylenediaminetetraacetic acid (EDTA, 89 %). The antibiofilm efficacy of 2-hydroxy-4-pyrone derivatives, alone and in combination with antibiotics, was evaluated by measuring the total biomass, metabolic activity, and culturability of biofilm cells. Furthermore, their impact on the membrane integrity of S. aureus biofilm cells was investigated using flow cytometry and epifluorescence microscopy with propidium iodide staining. It was also examined the ability of 2-hydroxy-4-pyrone derivatives and 2-hydroxy-4-pyrone derivate-antibiotic dual-combinations in inhibiting the production of virulence factors (total proteases, lipases, gelatinases and siderophores) by S. aureus. Regarding biofilm formation, the results showed that 2-hydroxy-4-pyrone derivatives alone reduced the metabolic activity of S. aureus biofilm cells by over 40 %. When combined with tobramycin, a 2-log (CFU cm-2) reduction in S. aureus biofilm cells was observed. Moreover, the combination of maltol and kojic acid with ciprofloxacin prevented P. aeruginosa biomass production by 60 %, compared to 36 % with ciprofloxacin alone. In pre-established S. aureus and P. aeruginosa biofilms, selected compounds reduced the metabolic activity by over 75 %, and a 3-log (CFU cm-2) reduction in the culturability of biofilm cells was noted when kojic acid and maltol were combined with antibiotics. Moreover, 2-hydroxy-4-pyrone derivatives alone and in combination with tobramycin, damaged the cell membranes of pre-established biofilms and completely inhibited total proteases production. Despite the increasing of reactive oxygen species production caused by the cellular treatment of maltol, both 2-hydroxy-4-pyrone derivatives showed good safe profile when tested in human hepatocarcinoma (HepG2) cells. The pre-treatment of HepG2 cells with both compounds was crucial to prevent the cellular damage caused by iron (III). This study demonstrates for the first time that the selected 2-hydroxy-4-pyrone derivatives significantly enhance the antibiofilm activity of tested antibiotics against S. aureus and P. aeruginosa, highlighting their potential as antibiotic adjuvants in preventing and eradicating biofilm-related infections.

Coral reefs are hotspots of marine biodiversity, which results in the synthesis of a wide variety of compounds with unique molecular scaffolds, and bioactivities, rendering reefs an ecosystem of interest. The chemodiversity stems from the intricate relationships between inhabitants of the reef, as the chemistry produced partakes in intra- and interspecies communication, settlement, nutrient acquisition, and defense. However, the coral reefs are declining at an unprecedented rate due to climate change, pollution, and increased incidence of pathogenic diseases. Among pathogens, Vibrio spp. bacteria are key players resulting in high mortality. Thus, alternative strategies such as application of beneficial bacteria isolated from disease-resilient species are being explored to lower the burden of pathogenic species. Here, we apply coculturing of a coral-derived pathogenic species of Vibrio and beneficial bacteria and leverage recent advancements in untargeted metabolomics to discover engineerable beneficial traits. By chasing chemical change in coculture, we report Microbulbifer spp.-mediated degradation of amphibactins, produced by Vibrio spp. bacteria to sequester iron. Additional biochemical experiments revealed that the degradation occurs in the peptide backbone and requires the enzyme fraction of Microbulbifer. A reduction in iron affinity is expected due to the loss of one Fe(III) binding moiety. Therefore, we hypothesize that this degradation shapes community behaviors as it pertains to iron acquisition, a limiting nutrient in the marine environment, and survival. Furthermore, Vibrio sp. bacteria suppressed natural product synthesis by beneficial bacteria. Understanding biochemical mechanisms behind these interactions will enable engineering probiotic bacteria capable of lowering pathogenic burdens during heat waves and incidence of disease.

Bacillibactin (BB) is a microbial siderophore produced by Bacillus species. BB is biosynthesized from 2,3-dihydroxybenzoic acid (2,3-DHB), Gly, and L-Thr by nonribosomal peptide synthetase (NRPS) enzymes DhbE, DhbB, and DhbF. The biosynthetic gene cluster (dhb) is also conserved in some strains of thermophilic genera, Geobacillus, Anoxybacillus and Parageobacillus. However, the production of BB from these thermophilic bacteria has not been characterized. Here, we report in vivo and in vitro characterization of BB biosynthesis in Parageobacillus sp. KH3-4 which grows at 65 °C. We confirmed BB production in this thermophilic bacterium and the gene cluster active. In vitro enzymatic analysis revealed that 4'-phosphopantetheinyltransferase (PPTase) encoded in the same gene cluster is responsible for the post-translational maturation of carrier proteins. DhbE and DhbF showed substrate preference to 2,3-DHB and Gly and L-Thr, respectively, consistent with the chemical structure of BB. With the purified enzymes, we successfully reconstituted the NRPS assembly line in vitro. In addition, using chemically synthesized acyl-N-acetylcysteamine substrate analogues, BB analogues possessing methylbenzoyl groups instead of 2,3-DHB were detected. This study provides a new insight into secondary metabolism in thermophiles, and it expands the temperature limitation of NRPS enzymes.

In this study, we identified and analyzed a novel genomic island (GI), named pddGI-1, located on chromosome II of certain strains of the marine pathogen Photobacterium damselae subsp. damselae (Pdd). This GI shares structural similarities with other GIs found in Vibrio species, such as the Vibrio seventh pandemic island-II (VSP-II) of V. cholerae. The pddGI-1 island is a mosaic of gene blocks that encode functions related to ROS defense, anaerobic energy metabolism, and restriction-modification (RM) systems. Notably, pddGI-1 also includes a complete vibrioferrin siderophore system, enabling the bacteria to thrive in low-iron environments. Vibrioferrin was chemically identified from cell-free supernatants of Pdd RG91. Additionally, a pvsD mutant deficient in vibrioferrin biosynthesis was generated and analyzed. The results suggest that Pdd strains harbouring pddGI-1 gain a distinct growth advantage under iron-limited conditions. These findings, along with previous research, highlight the significant heterogeneity in iron assimilation systems among Pdd strains.

Antibiotics have remained the cornerstone for the treatment of bacterial infections ever since their discovery in the twentieth century. The uproar over antibiotic resistance among bacteria arising from genome plasticity and biofilm development has rendered current antibiotic therapies ineffective, urging the development of innovative therapeutic approaches. The development of antibiotic resistance among bacteria has further heightened the clinical failure of antibiotic therapy, which is often linked to its low bioavailability, side effects, and poor penetration and accumulation at the site of infection. In this review, we highlight the potential use of siderophores, antibodies, cell-penetrating peptides, antimicrobial peptides, bacteriophages, and nanoparticles to smuggle antibiotics across impermeable biological membranes to achieve therapeutically relevant concentrations of antibiotics and combat antimicrobial resistance (AMR). We will discuss the general mechanisms via which each delivery system functions and how it can be tailored to deliver antibiotics against the paradigm of mechanisms underlying antibiotic resistance.

Since the emergence of Mycobacterium tuberculosis (MBT) strains resistant to most currently used anti-tubercular drugs, there has been an urgent need to develop efficient drugs capable of modulating new therapeutic targets. Mycobacterial DNA gyrase is an enzyme that plays a crucial role in the replication and transcription of DNA in MBT. Consequently, targeting this enzyme is of particular interest in developing new drugs for the treatment of drug-resistant tuberculosis, including multidrug-resistant tuberculosis (MDR-TB) and extensively drug-resistant tuberculosis (XDR-TB).

In the present study, multiple computational tools were adopted to screen a microbial-based natural products database (NPAtlas) for potential inhibitors of the ATPase activity of MBT DNA gyrase.

Twelve hits were initially identified as the top candidates based on their docking scores (ranging from -9.491 to -10.77 kcal/mol) and binding free energies (-60.37 to -73.21 kcal/mol). Following this, computational filters, including ADME-T profiling and pharmacophore modeling, were applied to further refine the selection. As a result, three compounds 1-Hydroxy-D-788-7, Erythrin, and Pyrindolol K2 emerged as the most promising, exhibiting favorable drug-like properties. Notably, 1-Hydroxy-D-788-7, an anthracycline derivative, demonstrated superior binding affinity in molecular dynamics simulations. The RMSD values, ranging from 1.7 to 2.5 Å, alongside RMSF analysis and a detailed evaluation of the established interaction forces, revealed that 1-Hydroxy-D-788-7 was the strongest binder to Mycobacterial DNA Gyrase B. The stable binding and favorable interaction profile highlighted 1-Hydroxy-D-788-7 as a top hit. These comprehensive computational findings strongly support the potential of 1-Hydroxy-D-788-7 as an effective anti-TB lead compound, warranting further experimental validation to confirm its therapeutic efficacy.

Bacterial social interactions play crucial roles in various ecological, medical, and biotechnological contexts. However, predicting these interactions from genome sequences is notoriously difficult. Here, we developed bioinformatic tools to predict whether secreted iron-scavenging siderophores stimulate or inhibit the growth of community members. Siderophores are chemically diverse and can be stimulatory or inhibitory depending on whether bacteria have or lack corresponding uptake receptors. We focused on 1928 representative Pseudomonas genomes and developed an experimentally validated coevolution algorithm to match encoded siderophore synthetases to corresponding receptor groups. We derived community-level iron interaction networks to show that siderophore-mediated interactions differ across habitats and lifestyles. Specifically, dense networks of siderophore sharing and competition were observed among environmental and nonpathogenic species, while small, fragmented networks occurred among human-associated and pathogenic species. Together, our sequence-to-ecology approach empowers the analyses of social interactions among thousands of bacterial strains and offers opportunities for targeted intervention to microbial communities.

Antibody-recruiting molecules (ARMs) have emerged as a promising strategy for enhancing immune responses against pathogens and cancer cells. In this study, we developed a novel class of antibacterial ARMs utilizing siderophores, small iron-chelating compounds, as targeting motifs. Siderophores naturally exhibit high specificity for bacterial pathogens due to their role in iron acquisition, making them ideal candidates for selective targeting. We identified a potent ARM, GNP3, comprising MECAM, a siderophore mimetic, and 2,4-dinitrophenyl (DNP), a motif recognized by endogenous antibodies, connected via a flexible linker. GNP3 binds simultaneously to both anti-DNP antibody and the siderophore receptor, FepA, facilitating the targeted deposition of antibodies on the surface of FepA-expressing bacterial cells, such as Escherichia coli and Pseudomonas aeruginosa. This GNP3-induced opsonization promoted robust immune responses, including complement-dependent cytotoxicity (CDC) in the presence of serum and macrophage-mediated phagocytosis. Moreover, GNP3 effectively triggered CDC activity against serum-resistant uropathogenic E. coli. The results suggest that siderophore-based ARMs, by harnessing the immune defense system, represent a promising complementary approach to traditional antibiotics for overcoming recalcitrant bacterial infections.

In response to iron deficiency and other environmental stressors, cyanobacteria producing siderophores can help in ameliorating plant stress and enhancing growth physiological and biochemical processes. The objective of this work was to screen the potential of Arthrospira platensis, Pseudanabaena limnetica, Nostoc carneum, and Synechococcus mundulus for siderophore production to select the most promising isolate, then to examine the potentiality of the isolated siderophore in promoting Zea mays seedling growth in an iron-limited environment.

Data of the screening experiment illustrated that Synechococcus mundulus significantly recorded the maximum highest siderophore production (78 ± 2%) while the minimum production was recorded by Nostoc carneum (24.67 ± 0.58%). Therefore, Synechococcus mundulus was chosen for the beneficiary study and the intended agricultural application. Siderophore-type identification tests proved that Synechococcus mundulus produced hydroxamate-type. The response surface approach was successful in optimizing the conditions of siderophore production in Synechococcus mundulus with actual values for maximum biomass (387.11 mg L- 1) and siderophore production (91.84%) higher than the predicted values. The proton nuclear magnetic resonance (1H NMR) analysis data and the Fourier transformer-infrared spectrum analysis (FT-IR) signify the hydroxamate nature of Synechococcus mundulus isolated siderophore. Zea mays seedlings' growth response in the hydroponic system was significantly stimulated in response to supplementation with Synechococcus mundulus siderophore in the absence of iron compared to plants grown without iron and the positive controls. Additionally, the contents of chlorophyll a, chlorophyll b, carotenoids, total carbohydrates, and total protein were all surpassed in siderophore-treated plants, which is expected due to the increased iron content.

The results introduced in this study highlighted the significant potential of Synechococcus mundulus-derived siderophore in stimulating Zea mays physicochemical growth parameters and iron uptake. Findings of this study present novel visions of cyanobacteria producing siderophores as an ecofriendly alternative candidate to synthetic iron chelators and their role in plant stress management.

Cyclic compounds are generally preferred over linear compounds for functional studies due to their enhanced bioavailability, stability towards metabolic degradation, and selective receptor binding. This has led to a need for effective cyclization strategies for compound synthesis and hence increased interest in macrocyclization mediated by thioesterase (TE) domains, which naturally boost the chemical diversity and bioactivities of cyclic natural products. Many non-ribosomal peptide synthetase (NRPS) and polyketide synthase (PKS) derived natural products are assembled to form cyclodimeric compounds, with these molecules possessing diverse structures and biological activities. There is significant interest in identifying the biosynthetic pathways that produce such molecules given the challenge that cyclodimerization represents from a biosynthetic perspective. In the last decade, many groups have pursued the characterization of TE domains and have provided new insights into this biocatalytic machinery: however, the enzymes involved in formation of cyclodimeric compounds have proven far more elusive. In this review we focus on natural products that involve macrocyclization in their biosynthesis and chemical synthesis, with an emphasis on the function and biosynthetic investigation on the special family of TE domains responsible for forming cyclodimeric natural products. We also introduce additional macrocyclization catalysts, including butelase and the CT-mediated cyclization of peptides, alongside the formation of cyclodipeptides mediated by cyclodipeptide synthases (CDPS) and single-module NRPSs. Due to the interdisciplinary nature of biosynthetic research, we anticipate that this review will prove valuable to synthetic chemists, drug discovery groups, enzymologists, and the biosynthetic community in general, and inspire further efforts to identify and exploit these biocatalysts for the formation of novel bioactive molecules.

Iron is an essential nutrient for the growth, survival and virulence of almost all bacteria. To access iron, many bacteria produce siderophores, molecules with a high affinity for iron. Research has highlighted substantial diversity in the chemical structure of siderophores produced by bacteria, as well as remarkable variety in the molecular mechanisms involved in strategies for acquiring iron through these molecules. The metal-chelating properties of siderophores, characterized by their high affinity for iron and ability to chelate numerous other metals (albeit with lower affinity compared with iron), have also generated interest in diverse fields. Siderophores find applications in the environment, such as in bioremediation and agriculture, in which emerging and innovative strategies are being developed to address pollution and enhance nutrient availability for plants. Moreover, in medicine, siderophores could be used as a tool for novel antimicrobial therapies and medical imaging, as well as in haemochromatosis, thalassemia or cancer treatments. This Review offers insights into the diversity of siderophores, highlighting their potential applications in environmental and medical contexts.

Microbes in soil navigate interactions by recognizing kin, forming social groups, exhibiting antagonistic behavior, and engaging in competitive kin rivalry. Here, we investigated a novel phenomenon of self-growth suppression (sibling rivalry) observed in Bradyrhizobium diazoefficiens USDA 110. Swimming colonies of USDA 110 developed a distinct demarcation line and inter-colony zone when inoculated adjacent to each other. In addition to self, USDA 110 suppressed growth of other Bradyrhizobium strains and several other soil bacteria. We demonstrated that the phenomenon of sibling rivalry is due to growth suppression but not cell death. The cells in the inter-colony zone were culturable but had reduced respiratory activity, ATP levels, and motility. The observed growth suppression was due to the presence of a diffusible effector compound. This effector was labile, preventing extraction, and identification, but it is unlikely a protein or a strong acid or base. This counterintuitive phenomenon of self-growth suppression suggests a strategic adaptation for conserving energy and resources in competitive soil environments. Bradyrhizobium's utilization of antagonism including self-growth suppression likely provides a competitive advantage for long-term success in soil ecosystems.

Bacteria have a stringent response system mediated by guanosine pentaphosphate and tetraphosphate ((p)ppGpp), which suppresses the expression of genes involved in cell growth and promotes the expression of genes involved in nutrient uptake and metabolism under nutrient-limited stress. In environments with limited availability of iron, an essential trace element, bacteria generally produce and secrete siderophores to efficiently utilize water-insoluble ferric iron (Fe3+) in the environment. In Vibrio parahaemolyticus, Fur (iron-responsive repressor) and RyhB (Fur-regulated small RNA) regulate the expression of genes involved in the utilization of vibrioferrin (VF), a siderophore produced by this bacterium. In this study, we examined whether (p)ppGpp is also involved in regulating the expression of genes related to the VF utilization system. Results of the chrome azurol S plate assay revealed that the strain in which 3 (p)ppGpp synthetases were deleted (∆relA∆spoT∆relV) produced less VF than the parental strain. Growth test results showed that the growth rate of ∆relA∆spoT∆relV in an iron-limited medium was suppressed compared with that of the parental strain but was restored with the addition of VF. Furthermore, RT-quantitative (q)PCR results showed that the expression levels of pvsA (VF biosynthesis gene) and pvuA2 (ferric VF receptor gene) in ∆relA∆spoT∆relV under iron limitation were significantly reduced compared with those in the parental strain. Western blot results demonstrated that the expression level of PvuA2 in ∆relA∆spoT∆relV was lower than that in the parental strain. These results suggest that (p)ppGpp promotes the expression of genes related to VF biosynthesis and the ferric VF uptake system under iron limitation.

Bacteria secrete siderophores to sequester the scarce iron in the environments, then the iron is transported into the cell in a siderophore-complexed form, which can be released by siderophore-interacting protein (SIP). Vibrio species comprise an array of serious pathogens, whose iron releasing process by SIP remains poorly understood. Herein, we report the high-resolution (1.2 Å) structure of Vibrio anguillarum SIP (VaSIP) in complex with FAD, representing the first structure of Vibrio SIP. VaSIP consists of a FAD-bound β-barrel domain and a Rossmann-fold domain connected by a linker, like other subgroup I SIPs. FAD is bound to the inter-domain cavity by aromatic stacking and hydrogen bonding interactions. Structural comparison indicated a modified NAD(P)H-binding motif (DxTA-EVL-GE) for subgroup I SIPs. The putative siderophore-binding pocket of VaSIP contains three lysines to form the basic triad to bind siderophore. Phylogenetic analysis shows Vibrio SIPs are mainly divided into two clades, represented by VaSIP and Vibrio cholerae ViuB, respectively. Interestingly, the two clades adopt distinct siderophore-binding basic triads, suggesting functional divergence among Vibrio SIPs. Our results shed light on the structural and phylogenetic characteristics of Vibrio SIPs, providing molecular basis for understanding Vibrio iron metabolism and designing anti-Vibrio drugs.

Dysfunction of the intestinal barrier is a prevalent phenomenon observed across a spectrum of diseases, encompassing conditions such as mesenteric artery dissection, inflammatory bowel disease, cirrhosis, and sepsis. In these pathological states, the integrity of the intestinal barrier, which normally serves to regulate the selective passage of substances between the gut lumen and the bloodstream, becomes compromised. This compromised barrier function can lead to a range of adverse consequences, including increased permeability to harmful substances, the translocation of bacteria and their products into systemic circulation, and heightened inflammatory responses within the gut and beyond. Understanding the mechanisms underlying intestinal barrier dysfunction in these diverse disease contexts is crucial for the development of targeted therapeutic interventions aimed at restoring barrier integrity and ameliorating disease progression. Lipocalin-2 (LCN2) expression is significantly upregulated during episodes of intestinal inflammation, making it a pivotal indicator for gauging the extent of such inflammatory processes. Notably, however, LCN2 derived from distinct cellular sources, whether intestinal epithelial cells or immune cells, exhibits notably divergent functional characteristics. Furthermore, the multifaceted nature of LCN2 is underscored by its varying roles across different diseases, sometimes even demonstrating contradictory effects.

Interspecies interactions involving direct competition via bacteriocin production play a vital role in shaping ecological dynamics within microbial ecosystems. For instance, the ribosomally produced siderophore bacteriocins, known as class IIb microcins, affect the colonization of host-associated pathogenic Enterobacteriaceae species. Notably, to date, only five of these antimicrobials have been identified, all derived from specific Escherichia coli and Klebsiella pneumoniae strains. We hypothesized that class IIb microcin production extends beyond these specific compounds and organisms. With a customized informatics-driven approach, screening bacterial genomes in public databases with BLAST and manual curation, we have discovered 12 previously unknown class IIb microcins in seven additional Enterobacteriaceae species, encompassing phytopathogens and environmental isolates. We introduce three novel clades of microcins (MccW, MccX, and MccZ), while also identifying eight new variants of the five known class IIb microcins. To validate their antimicrobial potential, we heterologously expressed these microcins in E. coli and demonstrated efficacy against a variety of bacterial isolates, including plant pathogens from the genera Brenneria, Gibbsiella, and Rahnella. Two newly discovered microcins exhibit activity against Gram-negative ESKAPE pathogens, i.e., Acinetobacter baumannii or Pseudomonas aeruginosa, providing the first evidence that class IIb microcins can target bacteria outside of the Enterobacteriaceae family. This study underscores that class IIb microcin genes are more prevalent in the microbial world than previously recognized and that synthetic hybrid microcins can be a viable tool to target clinically relevant drug-resistant pathogens. Our findings hold significant promise for the development of innovative engineered live biotherapeutic products tailored to combat these resilient bacteria.

In the search for iron, an essential element in many biochemical processes, microorganisms biosynthesise dedicated chelators, known as siderophores, to sequester iron from their environment and actively transport the siderophore complex into the cell. This process has been implicated in bacterial pathogenesis and exploited through siderophore-antibiotic conjugates as a method for selective antibiotic delivery. Here we review this Trojan-horse approach including design considerations and potential in diagnostics and infection imaging.

The resistance mechanism of Gram-negative bacteria to the siderophore antibiotic cefiderocol is primarily attributed to carbapenemase and siderophore uptake pathways; however, specific factors and their relationships remain to be fully elucidated. Here, we constructed cefiderocol-resistant Klebsiella pneumoniae (CRKP) strains carrying different carbapenemases and knocked out siderophore genes to investigate the roles of various carbapenemases and siderophores in the development of cefiderocol resistance. Antimicrobial susceptibility testing revealed that both blaNDM and blaKPC significantly increased the minimum inhibitory concentration (MIC) of Klebsiella pneumoniae (KP) to cefiderocol, while blaOXA-48 showed a modest increase. Notably, KP expressing NDM exhibited a higher cefiderocol MIC compared to KP expressing KPC, although expression of NDM alone did not induce cefiderocol resistance. Laboratory evolutionary experiments demonstrated that combining pNDM with mutations in the siderophore uptake receptor gene cirA and pKPC with a mutation in the two-component system gene envZ led to KP reaching a high level of cefiderocol resistance. Although combining pOXA with mutations in the two-component system gene baeS did not induce cefiderocol resistance, it significantly reduced susceptibility. Moreover, siderophores could influence the development of cefiderocol resistance. Strains deficient in enterobactin exhibited increased susceptibility to cefiderocol, while deficiencies in yersiniabactin and salmochelin showed no significant alterations. In conclusion, carbapenemase gene expression facilitates cefiderocol resistance, but its presence alone is insufficient. Cefiderocol resistance in CRKP typically involves abnormal expression of certain genes and other factors, such as mutations in siderophore uptake receptor genes and two-component system genes. The enterobactin siderophore synthesis gene entB may also contribute to resistance.

Mycobacterium tuberculosis (Mtb), the causative agent of tuberculosis (TB), faces iron scarcity within the host due to immune defenses. This review explores the importance of iron for Mtb and its strategies to overcome iron restriction. We discuss how the host limits iron as an innate immune response and how Mtb utilizes various iron acquisition systems, particularly the siderophore-mediated pathway. The review illustrates the structure and biosynthesis of mycobactin, a key siderophore in Mtb, and the regulation of its production. We explore the potential of targeting siderophore biosynthesis and uptake as a novel therapeutic approach for TB. Finally, we summarize current knowledge on Mtb's iron acquisition and highlight promising directions for future research to exploit this pathway for developing new TB interventions.

Iron is an essential micronutrient for almost every living organism, namely pathogenic bacteria. In an infection scenario, host-pathogen competitive relationships for the element are present and Fe withholding is a well known response of the host. Also, bacterial resistance is a major concern that can compromise public health and the WHO underlines an urgent need to search for new pharmaceutical ingredients or strategies to fight opportunistic bacteria. Iron metabolism, and in particular, deprivation is a strategy that currently constitutes another option to fight bacterial infection. In this work we report the synthesis of a new hexadentate chelator with enhanced hydrophilicity (MRHT) and the improved synthesis of two other chelators. The affinity towards charged and non-charged phospholipid bilayers was evaluated for three hexadentate chelators: MRHT, CP256 and RH8b using NMR and EPR spectroscopies. The results revealed that these structures, bearing 3,4-HPO units have a high affinity towards the hydrophilic region of the phospholipid bilayer. From the three hexadentate chelators, MRHT stood out, especially for liposomes with a charged surface, suggesting that this molecule could more efficiently compete with natural siderophores, creating an iron gradient near bacteria organisms.

To adapt to low-iron environments, many bacteria produce siderophores, low molecular weight iron chelators that are secreted into the environment where they bind ferric iron. The production of siderophore uptake systems then allows retrieval of the iron-complexed siderophore into the cell, where the metal ion can be used for structural and catalytic roles in many proteins. While many siderophores are produced by the activity of a family of large modular nonribosomal peptide synthetase (NRPS) enzymes, a second class of siderophores are produced by an alternate pathway. These so-called NRPS-independent siderophores (NIS) are biosynthesized through a shared catalytic step that is performed by an NIS synthetase. These enzymes catalyze the formation of an amide linkage between a carboxylate and an amine or, more rarely, form an ester with a hydroxyl substrate. Here we describe the discovery and biochemical studies of diverse NIS synthetases from different siderophore pathways to provide insight into their substrate specificity and catalytic mechanism. The structures of a small number of family members are additionally described that correlates the functional work with the enzyme structure. While the field has come a long way since it was described as a "long-overlooked" family in 2009, there remains much to discover in this large and important enzyme family.

Orangutans (Pongo abelii), as endemic primates of Indonesia, are characterized by a predominantly arboreal lifestyle. Klebsiella pneumoniae (K. pneumonia) and other Gram-negative bacteria are present in the Indigenous flora of many mammals, including orangutans. This study aimed to investigate the antibiotic resistance and virulence profile of K. pneumonia isolated from wild Sumatran orangutans.

This study investigated 10 fecal samples from wild Sumatran orangutans from the Gunung Leuser National Park, Aceh, Indonesia. Biochemical and molecular identification of K. pneumoniae using the RNA polymerase subunit b gene and detection of virulence-associated genes. In addition, molecular detection of antibiotic resistance genes was performed to characterize the resistance mechanisms in the isolates.

K. pneumonia was detected in 6 out of 10 fecal samples from wild Sumatran orangutans. The virulence genes mrkD and entB were detected in all (100%) of the isolates, whereas wabG was identified in 83.33% of the strains. Antibiotic susceptibility testing against K. pneumoniae revealed that three isolates were susceptible to streptomycin (S) and nalidixic acid (NA), while all six isolates were susceptible to chloramphenicol and ciprofloxacin. One isolate demonstrated intermediate resistance to NA, while the remaining two exhibited intermediate resistance to S. Six isolates were resistant to ampicillin, tetracycline, and erythromycin, indicating multidrug resistance. Furthermore, antibiotic resistance genes were detected in the isolates with the following prevalence: bla TEM gene (six isolates; 100%), bla SHV (six isolates; 100%), bla CTX-M gene (four isolates; 66.67%), and tetA gene (four isolates; 66.67%).

This study revealed the virulence and resistance profile of K. pneumoniae bacterium isolated from wild Sumatran orangutans, which is essential for formulating effective conservation and healthcare strategies.

Acinetobacter baumannii-a multidrug-resistant (MDR) pathogen that causes, for example, skin and soft tissue wounds; urinary tract infections; pneumonia; bacteremia; and endocarditis, particularly due to its ability to form robust biofilms-poses a significant challenge in clinical settings. This structure protects the bacteria from immune responses and antibiotic treatments, making infections difficult to eradicate. Given the rise in antibiotic resistance, alternative therapeutic approaches are urgently needed. Bacteriophage-based strategies have emerged as a promising solution for combating A. baumannii biofilms. Phages, which are viruses that specifically infect bacteria, offer a targeted and effective means of disrupting biofilm and lysing bacterial cells. This review explores the current advancements in bacteriophage therapy, focusing on its potential for treating A. baumannii biofilm-related infections. We described the mechanisms by which phages interact with biofilms, the challenges in phage therapy implementation, and the strategies being developed to enhance its efficacy (phage cocktails, engineered phages, combination therapies with antibiotics). Understanding the role of bacteriophages in both biofilm disruption and in inhibition of its forming could pave the way for innovative treatments in combating MDR A. baumannii infections as well as the prevention of their development.

The evolution of hypervirulent and carbapenem-resistant Klebsiella pneumoniae can be categorized into three main patterns: the evolution of KL1/KL2-hvKp strains into CR-hvKp, the evolution of carbapenem-resistant K. pneumoniae (CRKp) strains into hv-CRKp, and the acquisition of hybrid plasmids carrying carbapenem resistance and virulence genes by classical K. pneumoniae (cKp). These strains are characterized by multi-drug resistance, high virulence, and high infectivity. Currently, there are no effective methods for treating and surveillance this pathogen. In addition, the continuous horizontal transfer and clonal spread of these bacteria under the pressure of hospital antibiotics have led to the emergence of more drug-resistant strains. This review discusses the evolution and distribution characteristics of hypervirulent and carbapenem-resistant K. pneumoniae, the mechanisms of carbapenem resistance and hypervirulence, risk factors for susceptibility, infection syndromes, treatment regimens, real-time surveillance and preventive control measures. It also outlines the resistance mechanisms of antimicrobial drugs used to treat this pathogen, providing insights for developing new drugs, combination therapies, and a "One Health" approach. Narrowing the scope of surveillance but intensifying implementation efforts is a viable solution. Monitoring of strains can be focused primarily on hospitals and urban wastewater treatment plants.