Methylocystis silviterrae sp.nov., a high-affinity methanotrophic bacterium isolated from the boreal forest soil.

Abstract

A novel species is proposed for a high-affinity methanotrophic representative of the genus Methylocystis. Strain FST was isolated from a weakly acidic (pH 5.3) mixed forest soil of the southern Moscow area. Cells of FST are aerobic, Gram-negative, non-motile, curved coccoids or short rods that contain an intracytoplasmic membrane system typical of type-II methanotrophs. Only methane and methanol are used as carbon sources. FST grew at a temperature range of 4-37 °C (optimum 25-30 °C) and a pH range of 4.5 to 7.5 (optimum pH 6.0-6.5). The major fatty acids were C18 : 1ω8c, C18 : 1ω7c and C18 : 0; the major quinone as Q-8. FST displays 16S rRNA gene sequences similarity to other taxonomically recognized members of the genus Methylocystis, with Methylocystis hirsuta CSC1T (99.6 % similarity) and Methylocystis rosea SV97T (99.3 % similarity) as its closest relatives. The genome comprises 3.85 Mbp and has a DNA G+C content of 62.6 mol%. Genomic analyses and DNA-DNA relatedness with genome-sequenced members of the genus Methylocystis demonstrated that FST could be separated from its closest relatives. FST possesses two particulate methane monooxygenases (pMMO): low-affinity pMMO1 and high-affinity pMMO2. In laboratory experiments, it was demonstrated that FST might oxidize methane at atmospheric concentration. The genome contained various genes for nitrogen fixation, polyhydroxybutyrate synthesis, antibiotic resistance and detoxification of arsenic, cyanide and mercury. On the basis of genotypic, phenotypic and chemotaxonomic characteristics, it is proposed that the isolate represents a novel species, Methylocystis silviterrae sp. nov. The type strain is FST (=KCTC 82935T=VKM B-3535T).