Diversity and Phylogeny of Described Aerobic Methanotrophs

Abstract

Aerobic methanotrophs are metabolically unique bacteria that are able to utilize methane as a sole source of energy. They occur in a wide range of habitats where both methane and oxygen are available. Nearly all methanotrophic bacteria that are now isolated in pure cultures belong to the phylum Proteobacteria, while only a limited number of strains represent the Verrucomicrobia. Proteobacterial methanotrophs affiliate with the classes Gammaproteobacteria (type I methanotrophs) and Alphaproteobacteria (type II methanotrophs) and belong to 23 genera and 56 species with validly published names. Several described methanotrophic representatives of the Gammaproteobacteria are not yet obtained in pure cultures and have a “Candidatus” status. Cultivation-independent studies indicate the existence of several further groups of methanotrophic bacteria that have not yet been obtained in culture. However, the currently cultivated strains cover a surprisingly broad range of methanotrophs detected in various environments by molecular approaches. This chapter offers an overview of the currently described methanotroph diversity and the major groups of methanotrophic bacteria that have so far eluded isolation efforts.