Salinibacter iranicus sp. nov. and Salinibacter luteus sp. nov., isolated from a salt lake, and emended descriptions of the genus Salinibacter and of Salinibacter ruber

Abstract

Two Gram-staining-negative, red- and orange-pigmented, non-motile, rod-shaped, extremely halophilic bacteria, designated strains CB7(T) and DGO(T), were isolated from Aran-Bidgol salt lake, Iran. Growth occurred at NaCl concentrations of between 2 and 5 M NaCl and the isolates grew optimally with 3 M NaCl. The optimum pH and temperature for growth of the two strains were pH 7.5 and 37 °C, and they were able to grow over pH and temperature ranges of pH 6-8 and 25-50 °C. The predominant fatty acids of the two isolates were C(18:1)ω7c, iso-C(15:0) and summed feature 3 (C(16:1)ω7c and/or iso-C(15:0) 2-OH). The polar lipid pattern of the two isolates consisted of diphosphatidylglycerol, phosphatidylcholine, three unidentified lipids, one unidentified aminolipid and three unidentified glycolipids. The only quinone present was menaquinone 7 (MK-7). The G+C contents of the genomic DNA of strains CB7(T) and DGO(T) were 64.8 and 65.6 mol%, respectively. 16S rRNA gene sequence analysis indicated that strains CB7(T) and DGO(T) were related to Salinibacter ruber in the phylum Bacteroidetes. Levels of 16S rRNA gene sequence similarity between strains CB7(T) and DGO(T) and Salinibacter ruber DSM 13855(T) were 93.2 and 93.6%, respectively. The two novel strains shared 98.9% 16S rRNA gene sequence similarity. DNA-DNA hybridization experiments between strains CB7(T) and DGO(T) and Salinibacter ruber DSM 13855(T) indicated levels of relatedness of 44 and 52%, respectively, while the level of relatedness between the two new isolates was 53%. Chemotaxonomic data supported the placement of strains CB7(T) and DGO(T) in the genus Salinibacter. DNA-DNA hybridization studies and biochemical and physiological characterization allowed strains CB7(T) and DGO(T) to be differentiated from Salinibacter ruber and from each other. They are therefore considered to represent two novel species of the genus Salinibacter, for which the names Salinibacter iranicus sp. nov. (type strain CB7(T)=IBRC-M 10036(T)=CGMCC 1.11003(T)) and Salinibacter luteus sp. nov. (type strain DGO(T)=IBRC-M 10423(T)=CGMCC 1.11002(T)) are proposed. Emended descriptions of the genus Salinibacter and of Salinibacter ruber are also presented.