Halorubrum halophilum sp. nov., an extremely halophilic archaeon isolated from a salt-fermented seafood

A novel, red-pigmented, pleomorphic and short rod-shaped haloarchaeon, designated B8^T, was isolated from a salt-fermented seafood. Strain B8^T was found to be able to grow at 20–45 °C, in the presence of 15–30 % (w/v) NaCl and at pH 7.0–9.0. The optimum requirements were found to be a temperature range of 35–40 °C, pH 8.0 and the presence of 25 % NaCl. The cells of strain B8^T were observed to be Gram-staining negative and lysed in distilled water. Anaerobic growth did not occur in the presence of nitrate, l-arginine, dimethyl sulfoxide or trimethylamine N-oxide. The catalase and oxidase activities were found to be positive and nitrate was reduced in aerobic conditions. Tween 20, 40 and 80 were found to be hydrolyzed, whereas casein, gelatin and starch were not hydrolyzed. Indole or H₂S was not formed and urease activity was not detected. A phylogenetic analysis based on the 16S rRNA gene sequences indicated that strain B8^T is most closely related to members of the genus Halorubrum in the family Halobacteriaceae. Strain B8^T was found to have three 16S rRNA genes, rrnA, rrnB and rrnC; similarities between the 16S rRNA gene sequences are 99.0–99.8 %. Strain B8^T shared 99.0 % 16S rRNA gene sequence similarity with Halorubrum (Hrr.) lipolyticum JCM 13559^T and Hrr. saccharovorum DSM 1137^T, 98.8 % with Hrr. kocurii JCM 14978^T, 98.3 % with Hrr. lacusprofundi DSM 5036^T, 98.0 % with Hrr. arcis JCM 13916^T, 97.7 % with Hrr. aidingense JCM 13560^T and 97.0 % with Hrr. aquaticum JCM 14031^T, as well as 93.7–96.5 % with other type strains in the genus Halorubrum. The RNA polymerase subunit B′ gene sequence similarity of strain B8^T with Hrr. kocurii JCM 14978^T is 97.2 % and lower with other members of the genus Halorubrum. DNA–DNA hybridization experiments showed that strain B8^T shared equal or lower than 50 % relatedness with reference species in the genus Halorubrum. The genomic DNA G+C content of strain B8^T was determined to be 64.6 mol%. The major isoprenoid quinone of strain B8^T was identified as menaquinone-8 and the major polar lipids as phosphatidylglycerol, phosphatidylglycerol phosphate methyl ester, phosphatidylglycerol sulfate, sulfated mannosyl glucosyl diether and an unidentified phospholipid. Based on this polyphasic taxonomic study, strain B8^T is considered to represent a new species in the genus Halorubrum, for which the name Hrr. halophilum sp. nov. is proposed. The type strain is B8^T (=JCM 18963^T = CECT 8278^T).