Halorientalis persicus sp. nov., an extremely halophilic archaeon isolated from a salt lake and emended description of the genus Halorientalis.

An extremely halophilic archaeon, strain D108(T), was isolated from a brine sample of Aran-Bidgol salt lake in Iran. The novel strain was cream-pigmented, motile, pleomorphic rod-shaped and required at least 2.5 M NaCl but not MgCl2 for growth. Optimal growth was achieved with 4.3 M NaCl and 0.1 M MgCl2. The optimum pH and temperature for growth were pH 7.5 and 40 °C, respectively, and the strain was able to grow over a pH range of 6.5 to 9.0, and a temperature range of 30 to 50 °C. Phylogenetic analysis based on 16S rRNA gene sequence comparisons revealed that strain D108(T) clustered with the type strain of the sole species of the genus Halorientalis, Halorientalis regularis TNN28(T), with a sequence similarity of 98.8 %. The polar lipid pattern of strain D108(T) consisted of phosphatidylglycerol, phosphatidylglycerol phosphate methyl ester, one phosphoglycolipid and two glycolipids. The only quinone present was MK-8(II-H2). The DNA G+C content of strain D108(T) was 62.8 mol%. DNA-DNA hybridization studies (45 % with Halorientalis regularis IBRC-M 10760(T)), as well as biochemical and physiological characterization, allowed strain D108(T) to be differentiated from Halorientalis regularis. A novel species of the genus Halorientalis, Halorientalis persicus sp. nov., is therefore proposed to accommodate this strain. The type strain is D108(T) ( = IBRC-M 10043(T) = CECT 8375(T)). An emended description of the genus Halorientalis is also proposed.