Halovarius luteus gen. nov., sp nov., an extremely halophilic archaeon from a salt lake

An extremely halophilic archaeon, strain DA50(T), was isolated from a brine sample of Urmia lake, a hypersaline environment in north-west Iran. Strain DA50(T) was orange-pigmented, motile, pleomorphic and required at least 2.5 M NaCl but not MgCl2 for growth. Optimal growth was achieved at 4.0 M NaCl and 0.3 M MgCl2. The optimum pH and temperature for growth were pH 7.0 and 45 degrees C, while it was able to grow over a pH range of 6.5-8.0 and a temperature range of 25-50 degrees C. Analysis of 16S rRNA gene sequences revealed that strain DA50(T) is a member of the family Halobacteriaceae, showing a low level of similarity with other members of this family. Highest similarities, 94.4, 94.0 and 93.9 %, were obtained with the 16S rRNA gene sequences of the type strains of Natrialba aegyptia, Halobiforma lacisalsi and Halovivax asiaticus, respectively. Polar lipid analyses revealed that strain DA50(T) contains phosphatidylglycerol and phosphatidylglycerol phosphate methyl ester. Four unidentified glycolipids and two minor phospholipids were also observed. The only quinone present was MK-8(II-H-2). The G+C content of its DNA was 62.3 mol%. On the basis of the data obtained, the new isolate could not be classified in any recognized genus. Strain DA50(T) is thus considered to represent a novel species of a new genus within the family Halobacteriaceae, order Halobacteriales, for which the name Halovarius luteus gen. nov., sp. nov. is proposed. The type strain of Halovarius luteus is DA50(T) (=IBRC-M 10912(T)=CECT 8510(T)).