Mammalian Uteri Contain a Diverse Virome: Insights from Healthy Mares

The Earth’s estimated 10 ³¹ virions, primarily phages, significantly impact microbial ecosystems. Despite their abundance, viromes remain relatively understudied. This is especially the case in domestic animals. Although recent studies have described the presence of a dynamic commensal microbiome in mammalian uteri, no studies have attempted to characterize the commensal virome in a mammalian uterus. In this study we have established for the first time the presence of a sparse, but diverse native virome in the equine uterus. The resulting virome database consists of 513 non-redundant viral genomes (>2 kb). Taxonomic annotations revealed a diverse virome dominated by Gammaretrovirus, Mamastrovirus, Sapovirus and Rosenblumvirus. Notably, 75% of the assembled genomes represented novel species. The phylogenetic tree unveiled distinct clades suggesting unexplored viral diversity with the uterine environment. Furthermore, bacterial hosts for equine uterine phages were predicted, aligning with previous studies’ findings. Most notably, the study identified antibiotic resistance genes within the virome, hinting at potential gene transfer mechanisms between bacteria and viruses. This study establishes the first uterine virome of any mammal, shedding light on a previously unexplored domain. The findings highlight the potential for phage therapy in reproductive infectious diseases and the importance of understanding the maternal gestational environment. Moreover, the study underscores the need for further studies to expand the uterine viromes, paving the way to deeper understanding of uterine microbiome and its implications for animal and human health.