Methylomonas paludis sp. nov., the first acid-tolerant member of the genus Methylomoas, from an acidic wetland

An aerobic methanotrophic bacterium was isolated from an acidic (pH 3.9) Sphagnum peat bog in north-eastern Russia and designated strain MG30T. Cells of this strain are Gram-negative, pale-pink-pigmented, non-motile, thick rods that are covered by large polysaccharide capsules and contain an intracytoplasmic membrane system typical of type I methanotrophs. They possess a particulate methane monooxygenase enzyme (pMMO) and utilize only methane and methanol. Carbon is assimilated via the ribulose-monophosphate pathway; nitrogen is fixed via an oxygen-sensitive nitrogenase. Strain MG30T grows in a pH range of 3.8-7.3 (optimum pH 5.8-6.4) and at temperatures between 8 and 30°C (optimum 20-25°C). The major cellular fatty acids are C16:1ω5t, C16:1ω8c, C16:1ω7c, and C14:0; the DNA G+C content is 48.5 mol%. The isolate belongs to the family Methylococcaceae of the class Gammaproteobacteria and displays 94.7-96.9% 16S rRNA gene sequence similarity to members of the genus Methylomonas. However, strain MG30T differs from all taxonomically characterized members of this genus by the absence of motility, the ability to grow in acidic conditions, and low DNA G+C content. Therefore, we propose to classify this strain as a novel, acid-tolerant species of the genus Methylomonas, Methylomonas paludis sp. nov. Strain MG30T (=DSM 24973T = VKM B-2745T) is the type strain.

Draft Genomes of Gammaproteobacterial Methanotrophs Isolated from Terrestrial Ecosystems

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