Methylocystis bryophila sp nov., a facultatively methanotrophic bacterium from acidic Sphagnum peat, and emended description of the genus Methylocystis (ex Whittenbury et al. 1970) Bowman et al. 1993

A novel species is proposed for two facultatively methanotrophic representatives of the genus Methylocystis, strains H2s(T) and S284, which were isolated from an acidic (pH 4.3) Sphagnum peat-bog lake (Teufelssee, Germany) and an acidic (pH 3.8) peat bog (European North Russia), respectively. Cells of strains H2sT and S284 are aerobic, Gram-negative, non-motile, curved coccoids or short rods that contain an intracytoplasmic membrane system typical of type-II methanotrophs. They possess both a soluble and a particulate methane monooxygenase (MMO); the latter is represented by two isozymes, pMMO1 and pMMO2. The preferred growth substrates are methane and methanol. In the absence of C-1 substrates, however, these methanotrophs are capable of slow growth on acetate. Atmospheric nitrogen is fixed by means of an aerotolerant nitrogenase. Strains H2sT and S284 grow between pH 4.2 and 7.6 (optimum pH 6.0-6.5) and at 8-37 degrees C (optimum 25-30 degrees C). The major fatty acids are C-18:1 omega 8c,C-18:1 omega 7c and C-16:1 omega 7c; the major quinone is Q-8. The DNA G+C content is 62.0-62.3 mol%. Strains H2s(T) and S284 share identical 16S rRNA gene sequences, which displayed 96.6-97.3 % similarity to sequences of other taxonomically characterized members of the genus Methylocystis. Therefore, strains H2s(T) and S284 are classified as members of a novel species, for which the name Methylocystis bryophila sp. nov. is proposed; strain H2s(T) (=DSM 21852(T) =VKM B-2545(T)) is the type strain.