Halogranum rubrum gen. nov., sp. nov., a halophilic archaeon isolated from a marine solar saltern

Two extremely halophilic archaea, strains RO2-11^T and HO2-1, were isolated from two Chinese marine solar salterns, Rudong solar saltern and Haimen solar saltern, respectively. Cells of the two strains were polymorphic and Gram-stain-negative; colonies were red-pigmented. The two strains grew at NaCl concentrations of 2.6-4.3 M (optimum 3.9 M) and required at least 0.1 M Mg²⁺ for growth. They were able to grow over a pH range of 6.0-8.0 and a temperature range of 20-50 °C, with optimal pH of 7.5 and optimal temperature of 37 °C. The major polar lipids of strain RO2-11^T and strain HO2-1 were phosphatidylglycerol, phosphatidylglycerol phosphate methyl ester and three glycolipids, two of them chromatographically identical to S-DGD-1 and DGD-1, the third unidentified. The 16S rRNA gene sequence similarity of strain RO2-11^T and strain HO2-1 was 99.3% and highest sequence similarity with the closest relative (Haloferax larsenii) was 91.4 %. Based on the data obtained, the two isolates could not be classified in any recognized genus of the family Halobacteriaceae. Strain RO2-11^T and strain HO2-1 are thus considered to represent a novel species of a new genus within the family Halobacteriaceae, for which the name Halogranum rubrum gen. nov., sp. nov. is proposed. The type strain is RO2-11^T (=CGMCC 1.7738^T =JCM 15772^T).