Unprecedented Diversity of ssDNA Phages from the Family Detected within the Gut of a Protochordate Model Organism ().

Phages (viruses that infect bacteria) play important roles in the gut ecosystem through infection of bacterial hosts, yet the gut virome remains poorly characterized. Mammalian gut viromes are dominated by double-stranded DNA (dsDNA) phages belonging to the order and single-stranded DNA (ssDNA) phages belonging to the family . Since the relative proportion of each of these phage groups appears to correlate with age and health status in humans, it is critical to understand both ssDNA and dsDNA phages in the gut. Building upon prior research describing dsDNA viruses in the gut of , a marine invertebrate model system used to study gut microbial interactions, this study investigated ssDNA phages found in the gut. We identified 258 genomes, which were dominated by novel members of the subfamily, but also represented several proposed phylogenetic groups (Alpavirinae, Aravirinae, Group D, Parabacteroides prophages, and Pequeñovirus) and a novel group. Comparative analyses between specimens with full and cleared guts, as well as the surrounding water, indicated that retains a distinct and highly diverse community of ssDNA phages. This study significantly expands the known diversity within the family and demonstrates the promise of as a model system for investigating their role in animal health.