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

A Gram-stain negative, alkaliphilic and halotolerant bacterium, designated CCL18T, 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 CCL18T belongs to the genus Pelagibacterium, with its two closest neighbours being Pelagibacterium halotolerans B2T (96.6 %, 16S rRNA gene sequence similarity) and Pelagibacterium luteolum 1_C16_27T (96.1 %). The predominant respiratory quinone of strain CCL18T 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 CCL18T and P. halotolerans B2T and 24.6 % relatedness to P. luteolum 1_C16_27T. Based on phylogenetic analysis, DNA-DNA hybridization and a range of physiological and biochemical characteristics, strain CCL18T was clearly distinguishable from the other strains of the genus Pelagibacterium. It was evident that strain CCL18T 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 CCL18T (=CGMCC 1.16231T=KCTC 62030T).