Me.thy.lo.mo'nas. N.L. pref. methylo‐ pertaining to the methyl radical; L. fem. n. monas unit; N.L. fem. n. Methylomonas methyl monad or methyl unit.

Proteobacteria / Gammaproteobacteria / Methylococcales / Methylococcaceae / Methylomonas

Straight or slightly curved rods 0.5-1.1 × 0.5-4.0 µm, occurring singly, in pairs, or in short chains. Some species form a polysaccharide‐containing cyst that is desiccation sensitive. Some species are motile by means of a single polar flagellum. Gram‐negative. Most species have a strictly aerobic respiratory metabolism, with oxygen as the electron acceptor. Obligate utilizers of methane and methanol for carbon and energy. No growth occurs on carbon–carbon‐bonded compounds. Some members of the genus can couple denitrification and methane oxidation. Fix formaldehyde by the ribulose monophosphate pathway. Ribulose‐1,5‐diphosphate carboxylase activity is absent. Some species fix atmospheric nitrogen via an oxygen‐sensitive nitrogenase. Some species form red, pink, and orange carotenoid non‐water‐soluble pigments. Mesophilic, growing between 10 and 40°C, optimal growth temperatures 25-30°C. Nonhalophilic. Some species are nonhalotolerant. Major fatty acids include C_14:0, C_16:1 ω8c_, C_16:1 ω7c_, C_16:1 ω6c_, C_16:1 ω5c_, C_16:1 ω5t, and C_16:0. 18-Methyleneubiquinone‐8 (MQ-8) is the predominant lipoquinone. Main polar lipids are phosphatidylglycerol and phosphatidylethanolamine. Habitat: Isolated from sediments of freshwater lakes and rivers, wetland muds, activated sludge and wastewater, coal mine drainage waters, and groundwater.

DNA G +C content (mol%): 47-59 (T_m, HPLC, genome sequences).

Type species: Methylomonas methanica Whittenbury and Krieg 1984b, 355^VP (Effective publication: Whittenbury and Krieg 1984a, 260.)