Autochthonous Bacteriophages in the Microbial Loop Structure of Different Biotopes of Lake Baikal

This article presents the results of research into autochthonous bacteriophages, a previously unknown element in the structure of the microbial loop in the ecosystem of deep oligotrophic Lake Baikal. Transmission electron microscopy was used to study the morphological diversity of phages in the water column, surface microlayer, and benthic biofilms formed at the interface between water and geological rocks (marble, granite, mica, quartz, amphibolite, gabbro, and urtite). This article presents data on the dimensional structure of autochthonous bacteriophages, as well as their quantity, seasonal dynamics, and vertical distribution from the surface to the maximum depth (1200 m) when compared with the content of bacteria. Several morphotypes of Baikal autochthonous bacteriophages affecting Pseudomonas aeruginosa have been isolated and characterized by molecular-genetic methods. The complete genomes of giant phage PaBG from the Myoviridae family and phage MD8 from the Siphoviridae family have been determined.