The interconnectedness of bacteriophages and profages

Profages have been evolving together with their bacterial hosts for many years. Due to this proximity, a number of profages are integrated into the regulatory network of their host. This review presents the ways in which profages, which are phage genomes integrated into the genomes of their hosts, affect the behavior and virulence of bacteria. The main section presents the life cycle of phages: lytic, lysogenic, chronic infection, pseudolysogeny. The mechanism of induction of profages and the factors influencing it are presented. 51 of the 82 such genomes published to date carry profages, and they contain 230 putative recognizable profages. Profages can make up up to 10–20 % of the bacterial genome and make the main contribution to the differences between bacteria within the species. Moderate phages, which are involved in lysogenesis, carry out horizontal gene transfer. This review presents data from domestic and international scientific literature showing the important role of profages in the composition of the intestinal microbiota.