Halovivax cerinus sp. nov., an extremely halophilic archaeon from a hypersaline lake

Abstract

An extremely halophilic archaeon, strain IC35(T), was isolated from a mud sample of the Aran-Bidgol salt lake in Iran. The novel strain was cream, non-motile, rod-shaped and required at least 2.5 M NaCl, but not MgCl2, for growth. Optimal growth was achieved with 3.4 M NaCl and 0.1 M MgCl2. The optimum pH and temperature for growth were pH 7.0 (grew over a pH range of 6.5-9.0) and 40 °C (grew over a temperature range of 30-50 °C), respectively. Analysis of 16S rRNA gene sequences revealed that strain IC35(T) clustered with species of the genus Halovivax, with sequence similarities of 97.3%, 96.6% and 96.3%, respectively, to Halovivax limisalsi IC38(T), Halovivax asiaticus EJ-46(T) and Halovivax ruber XH-70(T). The rpoB' gene similarities between the novel strain and Halovivax limisalsi IBRC-M 10022(T), Halovivax ruber JCM 13892(T) and Halovivax asiaticus JCM 14624(T) were 90.2 %, 90.2% and 89.9%, respectively. The polar lipid pattern of strain IC35(T) consisted of phosphatidylglycerol and phosphatidylglycerol phosphate methyl ester; six unknown glycolipids and two minor phospholipids were also observed. The only quinone present was MK-8 (II-H2). The G+C content of the genomic DNA was 63.2 mol%. DNA-DNA hybridization studies (29% hybridization with Halovivax limisalsi IBRC-M 10022(T)), as well as biochemical and physiological characterization, allowed strain IC35(T) to be differentiated from other species of the genus Halovivax. A novel species, Halovivax cerinus sp. nov., is therefore proposed to accommodate this strain. The type strain is IC35(T) ( = IBRC-M 10256(T) = KCTC 4050(T)).