Variation in the gut microbiota of monozygotic twins is mirrored in their viromes

The gut microbiome includes the virome, virus populations that far outnumber the microbiota. The virome is composed largely of bacteriophage and likely interact with, and partially shape, the microbiota. An understanding how the virome impacts human health is limited at present by a lack of basic knowledge about what determines its diversity and how it relates to the rest of the microbiome. Host genetics and environmental factors are known to drive variation in the microbiota and the virome, but these factors often co-vary and their effects are confounded. Here, we make use of monozygotic (MZ) twins to ask how gut microbiota diversity relates to virome diversity while controlling for host genotype. From 354 MZ twin pairs whose fecal microbiotas were previously characterized, we selected a set of 24 pairs with either concordant or discordant microbiotas and performed a metagenomic analysis of virus like particles isolated from the same stool. Analysis of the viromes' gene and diversity content revealed that MZ twin pairs with concordant microbiotas had more similar viromes than those with discordant microbiotas. These results show that environmentally driven variation in microbiota within MZ twins is reflected in their viromes, but the direction of the interactions remains to be clarified.