A novel, orange-pigmented, halophilic archaeon, strain DC8T, was isolated from Urmia salt lake in north-west Iran. The cells of strain DC8T were non-motile and pleomorphic, from small rods to triangular or disc shaped. The novel strain needed at least 2.5 M NaCl and 0.02 M MgCl2 for growth. Optimal growth was achieved at 4.0 M NaCl and 0.1 M MgCl2. The optimum pH and temperature for growth were pH 7.5 and 45 8C, respectively, and it was able to grow over a pH range of 7.0 to 8.5 and a temperature range of 25 to 55 8C. Analysis of the 16S rRNA gene sequence showed that strain DC8T was a member of the family Halobacteriaceae; however, its similarity was as low as 90.1 %, 89.3% and 89.1% to the most closely related haloarchaeal taxa, including type species of members of the genera Halosimplex, Halobaculum and Halomicrobium, respectively. The G+C content of its DNA was 68.1 mol%. Polar lipid analyses revealed that strain DC8T contained phosphatidylglycerol, phosphatidylglycerol phosphate methyl ester, phosphatidylglycerol sulfate and phosphatidic acid. One unknown phospholipid, two major glycolipids and one minor glycolipid were also detected. The only quinone present was MK-8 (II-H2). The physiological, biochemical and phylogenetic differences between strain DC8T and other extremely halophilic archaeal genera with validly published names supported that this strain represents a novel species of a new genus within the family Halobacteriaceae, for which the name Halosiccatus urmianus gen. nov., sp. nov. is proposed. The type strain is strain DC8T (5IBRC-M 10911T5CECT 8793T).

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