Natrinema salaciae sp. nov., a halophilic archaeon isolated from the deep, hypersaline anoxic Lake Medee in the Eastern Mediterranean Sea

Abstract

Two halophilic archaea, strains MDB25T and MDB20, were isolated from a sample of the brine from Lake Medee, at a depth of 3050m, in the Mediterranean Sea. Cells of the organisms were Gram-negative, non-motile and pleomorphic, and colonies were red pigmented. Strains MDB25T and MDB20 showed optimum growth at 45°C, in 2.6–3.4M NaCl and at pH 7.0–8.0. The major polar lipids of the two strains were phosphatidylglycerol (PG1 and PG2), phosphatidylglycerol phosphate methyl ester (PGP-Me) and mannose-2,6-dissulfate (1→2)-glucose glycerol diether (S2-DGD). Menaquinone MK-8 and MK-8(H2) were the major respiratory quinones. The DNA G+C content of strain MDB25T was 63.0%. The strains were facultatively anaerobic but grew better under aerobic conditions, nitrate served as electron acceptor. Analysis of the almost complete 16S rRNA gene sequence indicated that the strains MDB25T and MDB20 represented a member of the genus Natrinema in the family Halobacteriaceae. Both strains formed a distinct cluster and were most closely related to Natrinema ejinorense JCM 13890T and Haloterrigena longa JCM 13562T (98.0% and 97.9% sequence similarity, respectively). Based on 16S rRNA gene sequence analysis, DNA–DNA hybridization results, physiological and biochemical characteristics we describe a new species represented by strain MDB25T (=DSM 25055T =JCM 17869T) for which we propose the name Natrinema salaciae sp. nov.