Resumo

The genera Natrinema and Haloterrigena comprise several species that seem to be intermixed phylogenetically and may represent only one genus. These organisms have been isolated from a variety of hypersaline environments such as high salt fish sauce, salt terns and hypersaline lakes. Two halophilic archaea, strains MDB25^T and MDB20, were isolated from a sample of the brine from Medee Lake, at a depth of 3050 meters, in the Mediterranean Sea. Sample was collected during the R/V Urania cruise MIDDLE09 in September 2009. Cells of the organisms were Gram-negative, non-motile and pleomorphic, and colonies were red pigmented. Strains MDB25^T and MDB20 showed optimum growth at 45 ºC, in 2.6-3.4 M NaCl and at pH 7.0-8.0. The organisms were oxidase and catalase positive. 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 MDB25^T 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 MDB25 ^T 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 13890^T and Haloterrigena longa JCM 13562^T (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 MDB25^T (=DSM 25055^T =JCM 17869^T) for which we propose the name Natrinema salaciae sp. nov.