Comparison of gut viromes across captive mammals reveals extensive genetic diversity in bacteriophage dark matter and mammalian viruses.

Comprehensive characterization of mammalian gut viromes is essential for early detection of commensal and potentially zoonotic viruses and for reducing the risk of cross-species transmission. Viral metagenomics was applied to profile gut viral communities from zoo mammals maintained across multiple zoological institutions in China. Viral communities differed markedly among host dietary guilds, with herbivores exhibiting the highest viral species diversity. In total, 1 027 viral sequences representing five major viral groups were recovered, including multiple mammal-associated astroviruses, picornaviruses, and parvoviruses with potential infectivity. Phylogenetic reconstruction based on viral hallmark genes demonstrated extensive genomic diversification across recovered lineages. Hosts for most microviruses were predicted to belong to the bacterial family Bacteroidaceae. In addition, 10 previously unreported crAss-like phages were identified in mammalian samples and showed close evolutionary relationships with proposed crAssphages from the human gut virome. Antibiotic resistance genes identified in the mammalian gut viromes primarily belonged to tetracyclines. These findings substantially expand current understanding of viral community structure in captive animals in China and provide a foundation for proactive surveillance frameworks targeting emerging mammalian viruses with zoonotic potential.