Methylocella tundrae sp nov., a novel methanotrophic bacterium from acidic tundra peatlands

A novel species, Methylocella tundrae, is proposed for three methanotrophic strains (T4(T), TCh1 and TY1) isolated from acidic Sphagnum tundra peatlands. These strains are aerobic, Gram-negative, non-motile, dinitrogen-fixing rods that possess a soluble methane monooxygenase and utilize the serine pathway for carbon assimilation. Strains T4(T), TCh1 and TY1 are moderately aciclophilic organisms capable of growth between pH 4.2 and 7.5 (optimum 5.5-6.0) and between 5 and 30 degreesC (optimum 15 degreesC). The major phospholipid fatty acid is 18:1omega7c. The DNA G + C content of strain T4(T) is 63.3 mol%. The three strains possess almost identical 16S rRNA gene sequences and are most closely related to two previously identified species of Methylocella, Methylocella palustris (97% similarity) and Methylocella silvestris (97.5% similarity). DNA-DNA hybridization values of strain T4(T) with Methylocella palustris K-T and Methylocella silvestris BL2(T) were respectively 27 and 36%. Thus, the tundra strains represent a novel species, for which the name Methylocella tundrae sp. nov. is proposed. Strain T4(T) (=DSM 15673(T) = NCIMB 13949(T)) is the type strain.