Pelagibacterium montanilacus sp. nov., an alkaliphilic bacterium isolated from Lake Cuochuolong on the Tibetan Plateau.

A Gram-stain negative, alkaliphilic and halotolerant bacterium, designated CCL18, was isolated from Lake Cuochuolong on the Tibetan Plateau. The strain was aerobic, short rod-shaped, catalase- and oxidase-positive, and motile by means of several polar flagella. Phylogenetic analysis based on 16S rRNA gene sequencing indicated that strain CCL18 belongs to the genus Pelagibacterium, with its two closest neighbours being Pelagibacterium halotolerans B2 (96.6 %, 16S rRNA gene sequence similarity) and Pelagibacterium luteolum 1_C16_27 (96.1 %). The predominant respiratory quinone of strain CCL18 was Q-10, with Q-9 as a minor component. The major fatty acids were C18 : 1ω6c/C18 : 1ω7c (60.4 %), C19 : 0cyclo ω8c (8.1 %) and C18 : 0 (6.8 %). The polar lipids included phosphatidylglycerol, diphosphatidylglycerol, seven kinds of unidentified lipids and three kinds of glycolipids. The DNA G+C content was 60.1 mol%. DNA-DNA hybridization showed 35.2 % relatedness between strain CCL18 and P. halotolerans B2 and 24.6 % relatedness to P. luteolum 1_C16_27. Based on phylogenetic analysis, DNA-DNA hybridization and a range of physiological and biochemical characteristics, strain CCL18 was clearly distinguishable from the other strains of the genus Pelagibacterium. It was evident that strain CCL18 could be classified as a novel species of the genus Pelagibacterium, for which the name Pelagibacterium montanilacus sp. nov. is proposed. The type strain is CCL18 (=CGMCC 1.16231=KCTC 62030).