<i>Methylomonas Montana </i>sp. nov., the First Unpigmented Methanotroph of the Genus <i>Methylomonas</i>, Isolated from Mountain River Sediments

Abstract

Abstract—Aerobic methanotrophic bacteria of the genus Methylomonas inhabit a wide spectrum of habitats including freshwater bodies, river sediments, wetlands, rice paddies, landfill cover soils, and hydromorphic soils. Majority of the currently described species of this genus are represented by neutrophilic, motile, growing on methane rod-shaped bacteria, whose pigmentation varies from yellow to pink and red. This study reports characterization of a novel, unpigmented isolate of these bacteria, strain MW1T, which was obtained from sediments of the mountain river Khosta, Krasnodar region, Russia. Strain MW1T grew on methane and methanol within a temperature range of 8–37°C (optimum at 25–30°C) and at рН 5.5–7.5 (optimum at 6.3–7.0). The 16S rRNA gene sequence of strain MW1T displayed 95.48–98.47% similarity to those in earlier described Methylomonas. The closest taxonomically characterized phylogenetic relative of strain MW1T was M. fluvii EbBT, isolated from the river Elbe sediments. Complete genome sequence of strain MW1T was 4.6 Mb in size and contained three rRNA operons and about 4200 protein-encoding genes, including the gene cluster pmoCAB coding for membrane methane monooxygenase. Soluble methane monooxygenase was not encoded in the genome. The G+C DNA content was 52.4%. The average nucleotide identity of the genome of strain MW1T with those in earlier described representatives of the genus Methylomonas was 79.4–82.1%. We propose to classify this isolate as representing a novel species of the genus Methylomonas, M. montana sp. nov. Strain MW1T (=VKM 3737T = UQM 41536T) is the type strain of the newly proposed species.