Lytic Enzymes Encoded in the Genome of Methyloraptor flagellatus S20T

Methyloraptor flagellatus S20T is a recently described facultatively methylotrophic representative of the alphaproteobacterial family Ancalomicrobiaceae, which was isolated from a methane-fed bioreactor with methanotrophs of the genus Methylococcus. These methylotrophs are capable of attaching to methanotrophic cells and breaking the integrity of their cell walls, presumably to feed on methanol, the first product of methane oxidation. In this study, we analyzed the genetic determinants that define the ability of Methyloraptor flagellatus S20T to lyse the cell wall of its prey. The whole genome sequence analysis of strain S20T resulted in the identification of genes encoding potential lytic enzymes from the GH19, GH23, GH102, and GH103 families of glycoside hydrolases. The search for phylogenetically close experimentally characterized homologues of these enzymes identified GH19_1 subfamily lysozymes from several phages. GH19_1 subfamily proteins were also revealed in Methyloraptor-related methylotrophic bacteria of the species Prosthecodimorpha hirschii, which often occur in close association with methanotrophic bacteria, as well as in other described representatives of the Ancalomicrobiaceae. The presence of GH19_1 subfamily lysozymes in members of this family indicates their likely widespread participation in interactions with other bacteria.