Methylocapsa palsarum sp nov., a methanotroph isolated from a subArctic discontinuous permafrost ecosystem

An aerobic methanotrophic bacterium was isolated from a collapsed palsa soil in northern Norway and designated strain NE2(T). Cells of this strain were Gram-stain-negative, non-motile, non-pigmented, slightly curved thick rods that multiplied by normal cell division. The cells possessed a particulate methane monooxygenase enzyme (pMMO) and utilized methane and methanol. Strain NE2(T) grew in a wide pH range of 4.1-8.0 (optimum pH 5.2-6.5) at temperatures between 6 and 32 degrees C (optimum 18-25 degrees C), and was capable of atmospheric nitrogen fixation under reduced oxygen tension. The major cellular fatty acids were C-18 :1 omega 7c, C-16 : (0) and C-16 (: 1)omega 7c, and the DNA G+C content was 61.7 mol%. The isolate belonged to the family Beijerinckiaceae of the class Alphaproteobacteria and was most closely related to the facultative methanotroph Methylocapsa aurea KYG(T) (98.3 % 16S rRNA gene sequence similarity and 84 % PmoA sequence identity). However, strain NE2(T) differed from Methylocapsa aurea KYG(T) by cell morphology, the absence of pigmentation, inability to grow on acetate, broader pH growth range, and higher tolerance to NaCl. Therefore, strain NE2(T) represents a novel species of the genus Methylocapsa, for which we propose the name Methylocapsa palsarum sp. nov. The type strain is NE2(T) (=LMG 28715(T)=VKM B-2945(T)).