Psychroflexus curvus sp. nov., Psychroflexus longus sp. nov. and Psychroflexus montanilacus sp. nov., isolated from salt lakes on the Tibetan Plateau

Abstract

Four Gram-stain-negative, catalase- and oxidase-positive, rod-shaped and non-motile strains (CAK1WT, CAK8WT, CAK57W and CCL10WT) were isolated from salt lakes in China. Comparisons based on the 16S rRNA gene sequences showed that the four strains show less than 98.9% similarity to species of the genus Psychroflexus . The phylogenetic tree reconstructed based on 16S rRNA gene sequences also showed that Psychroflexus species are the most closely related neighbours of the four strains. The sequenced draft genome sizes of strains CAK1WT, CAK8WT, CAK57W and CCL10WT were 3.01, 2.95, 3.01 and 3.04 Mbp with G+C contents of 37.3, 35.8, 37.5 and 36.6 %, respectively. The phylogenomic trees reconstructed based on the UBCG and GET_PHYLOMARKERS pipelines all demonstrated that the four strains belong to the genus Psychroflexus . The calculated pairwise orthologous average nucleotide identity based on usearch, digital DNA–DNA hybridization and average amino acid sequence identity values among strains CAK1WT, CAK8WT, CAK57W, CCL10WT and other species of the genus Psychroflexus were equal or lower than 91.1, 43.5 and 92.2%; the values between strains CAK1WT and CAK57W were 98.8, 90.2 and 99.0 %, respectively. The respiratory quinone of the four strains was MK-6. Their major fatty acids were iso-C14 : 0, C15 : 1 ω10c, iso-C15 : 0 and anteiso-C15 : 0. The major polar lipids of the four strains included phosphatidylethanolamine, an unidentified aminolipid and two kinds of unidentified lipids, and only strain CCL10WT contained diphosphatidylglycerol. Based on the above descriptions, strains CAK1WT, CAK8WT, CAK57W and CCL10WT should belong to the genus Psychroflexus and represent three independent novel species, for which the names Psychroflexus curvus sp. nov. (type strain CAK1WT=GDMCC 1.2644T=KCTC 82857T), Psychroflexus longus sp. nov. (type strain CAK8WT=GDMCC 1.2646T=KCTC 82859T) and Psychroflexus montanilacus sp. nov. (type strain CCL10WT=GDMCC 1.2631T=KCTC 82860T) are proposed.