Novel Bacteriophages Infecting Contain Diversity Generating Retroelement.

Intestinal phages are abundant and important components of gut microbiota, yet the isolated and characterized representatives that infect abundant gut bacteria are sparse. Here we describe the isolation of human intestinal phages infecting . is one of the most common bacterial groups in the global human gut microbiota; however, to date not many specific phages are known. Phages isolated in this study belong to a novel viral genus, Bacuni, within the family. Their genomes encode diversity-generating retroelements (DGR), which were shown in other bacteriophages to promote phage adaptation to rapidly changing environmental conditions and to broaden their host range. Three isolated phages showed 99.83% genome identity but one of them infected a distinct strain. The tropism of Bacuni phages appeared to be dependent on the interplay of DGR mediated sequence variations of gene encoding putative phage fimbrial tip proteins and mutations in host genes coding for outer-membrane proteins. We found prophages with up to 85% amino acid similarity over two-thirds of the Bacuni phage genome in the and sp. genomes. Despite the abundance of within the human microbiome, we found Bacuni phages only in a limited subset of published gut metagenomes.