Unusual members of the PVC superphylum: The methanotrophic Verrucomicrobia genus Methylacidiphilum

Abstract

Aerobic methanotrophic bacteria can use methane as their sole energy source. Most known species belong to the phylum Proteobacteria. One exception is a group of thermoacidophilic methanotrophic bacteria belonging to the phylum Verrucomicrobia. Although not yet taxonomically validated, these bacteria have been described physiologically and genomically and given the tentative genus name Methylacidiphilum. They are found in geothermal environments with moderate to high temperatures (up to 65 °C) and high acidities (down to pH 1). The genetic pathways conferring a methanotrophic lifestyle in verrucomicrobial methanotrophs are similar to their proteobacterial counterparts, although rather than fixing carbon derived from methane, they are autotrophs obtaining carbon via the Calvin-Benson-Bassham cycle. Lateral gene transfer appears to have played a major role in shaping the genomes of Methylacidiphilum spp. The following chapter summarizes what we presently know about them.