Unveiling the viral dimension: The paediatric gut virome as a key modulator of gastrointestinal metabolic, and neurodevelopmental health

Table 1 Comparative landscape of the human gut bacteriome and virome

Metric	Gut bacteriome	Gut virome
Numerical abundance	1011-1012 cells per gram of feces	109-1012 particles per gram of feces (VLPs)1
Biomass contribution	Major (99.9% microbial biomass)	Minimal (< 0.1% of microbial biomass)
Universal genetic marker	Present (16S rRNA gene)	None (Requires shotgun metagenomics)
Database maturity	High (most sequences are identifiable)	Low (40%-90% “viral dark matter”)2
Identification logic	Taxonomy-based (16S) or functional	Homology-based or de novo assembly
Major constituents	Bacteria, archaea	Bacteriophages, eukaryotic viruses, archaeal viruses, and EVEs
Replication strategy	Predominantly binary fission	Lytic, lysogenic (prophages), and chronic
Pediatric trajectory	Diversity increases linearly with age	Richness often peaks in infancy and fluctuates
Study cost/complexity	Lower (standardized and high-throughput)	Higher (requires enrichment and heavy compute)

¹Numerical Paradox: While viruses often outnumber bacteria in particle count, their lack of biomass made them “invisible” to early bulk sequencing methods.

²Viral dark matter: Refers to sequences that do not align with any known reference in public databases.

EVEs: Endogenous viral elements; VLP: Virus-like particles.