Methylosarcina lacus sp. nov., a methanotroph from Lake Washington, Seattle, USA, and emended description of the genus Methylosarcina.

An obligately methanotrophic bacterial strain, LW14T, isolated from the sediment of Lake Washington, Seattle, USA, is described taxonomically. The isolate is an aerobic, Gram-negative, non-motile bacterium capable of growth on methane, and possesses type I intracytoplasmic membranes (i.e. it is a type I methanotroph). The strain possesses particulate methane monooxygenase (MMO) and has no soluble MMO. Formaldehyde is assimilated via the ribulose monophosphate cycle. The isolate grows within a pH range of 4-8, with the optimum between pH 5.5 and 6.5. The cellular fatty acid profile is dominated by C(16 : )omega18c, C(16 : 1)omega7c and C(16 : 1)omega5t fatty acids. The DNA G+C content is 53.3+/-0.4 mol%. On the basis of sequence analysis of the 16S rRNA gene, isolate LW14T is related most closely to representatives of the genus Methylosarcina. However, DNA-DNA hybridization analysis reveals only a distant relationship between isolate LW14T and the previously described Methylosarcina species. On the basis of its phenotypic and genotypic characteristics, LW14T represents a novel species of the genus Methylosarcina, for which the name Methylosarcina lacus sp. nov. is proposed, with LW14T (=ATCC BAA-1047T=JCM 13284T) as the type strain.