Glycoside Hydrolases of the Obligate Methanotroph <i>Methyloferula stellata</i>: an Unusual Evolutionary Strategy not Involving Distant Lateral Transfers

Abstract

Abstract—The genome of the obligately methanotrophic bacterium Methyloferula stellata AR4 encodes thirty glycoside hydrolases. The closest homologues for most of these proteins belong to other members of the class Alphaproteobacteria. Two exceptions are represented by the genes encoding glycoside hydrolases of the families GH39 and GH65, which presumably appeared in M. stellata AR4 due to the lateral transfer from distantly related bacteria. This work was devoted to the study of the evolutionary history of these two genes. In the case of a member of the GH65 family of glycoside hydrolases, this scenario was not confirmed. Kojibiose phosphorylase encoded by this gene is common among Alphaproteobacteria. The suggested lateral transfer of the corresponding gene had an opposite direction, into one of the evolutionary lineages of the class Betaproteobacteria. The potential glycoside hydrolase of the GH39 family was shown to be the only one which gene is not of proteobacterial origin. The role of lateral transfers in the evolution of glycoside hydrolases and their homologues in methanotrophs and other bacteria is discussed.