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

Abstract

A Gram-stain negative, alkaliphilic and halotolerant bacterium, designated CCL18^T, 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^T belongs to the genus Pelagibacterium, with its two closest neighbours being Pelagibacterium halotolerans B2^T (96.6 %, 16S rRNA gene sequence similarity) and Pelagibacterium luteolum 1_C16_27^T (96.1 %). The predominant respiratory quinone of strain CCL18^T 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^T and P. halotolerans B2^T and 24.6 % relatedness to P. luteolum 1_C16_27^T. Based on phylogenetic analysis, DNA-DNA hybridization and a range of physiological and biochemical characteristics, strain CCL18^T was clearly distinguishable from the other strains of the genus Pelagibacterium. It was evident that strain CCL18^T 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^T (=CGMCC 1.16231^T=KCTC 62030^T).