Methylomonas

Methylomonas is a genus of aerobic, Gram-negative methane-oxidizing bacteria in the family Methylococcaceae, order Methylococcales, class Gammaproteobacteria, phylum Proteobacteria. The type species is Methylomonas methanica.

Cells are typically small, rod-shaped, and occur singly or in pairs. Like other methanotrophs, they possess internal membrane structures associated with methane oxidation and are generally non-sporulating.

Methylomonas species oxidize methane as their sole carbon and energy source, converting methane to methanol via methane monooxygenase. Carbon is assimilated mainly through the ribulose monophosphate (RuMP) pathway. Most strains harbor the copper-dependent particulate methane monooxygenase (pMMO) encoded by the pmoCAB operon; some strains can express a soluble MMO (sMMO) under copper-limited conditions.

They are found in diverse aerobic environments where methane is available, including soils, wetlands and rice paddies, lake and river sediments, and engineered systems such as wastewater treatment plants and methanotrophic bioreactors.

Several species have sequenced genomes, revealing operons for methane oxidation (pmoCAB) and methanol oxidation (mxaFI), along with pathways for formaldehyde assimilation via RuMP. 16S rRNA gene analyses place Methylomonas among the Type I methanotrophs within Gammaproteobacteria.

Methylomonas and other methanotrophs are studied for methane mitigation and bioconversion of methane to biomass or value-added products. They also serve as model organisms for the study of methane oxidation and carbon fixation in aerobic bacteria.