Halorubrum aethiopicum sp. nov., an extremely halophilic archaeon isolated from commercial rock salt

A novel extremely halophilic archaeon, designated SAH-A6 T , was isolated from a sample of commercial rock salt in Ethiopia. Cells of SAH-A6 T were aerobic and pleomorphic. The strain was able to grow at concentrations of 15-30 % (w/v) NaCl (optimum 20-25 % NaCl), at pH 6.0-9.0 (optimum pH 7.0) and in a temperature range of 30-55 °C (optimum 37-45 °C). Mg 2+ was not required for growth of SAH-A6 T cells. On the basis of 16S rRNA gene sequence analysis, strain SAH-A6 T was closely related to Halorubrum halodurans Cb34 T (99.1 %), Halorubrum rubrum YC87 T (98.9 %), Halorubrum aquaticum EN-2 T (98.7 %), Halorubrum cibi JCM 15757 T (98.4 %), Halorubrum luteum CGSA15 T (97.3 %), Halorubrum lipolyticum 9-3 T (97.1 %), Halorubrum tibetense 8W8 T (97.1 %), Halorubrum kocurii JCM 1478 T (97.1 %), Halorubrum halophilum B8 T (97.0 %) and Halorubrum persicum C49 T (97.0 %). Phylogenetic analysis based on the rpoB' gene sequences showed that strain SAH-A6 T was closely related to Hrr. halodurans Cb34 T (99.7 %), Hrr. aquaticum JCM 14031 T (99.3 %) and other members of the genus Halorubrum (<99.0 %). The DNA G+C content of the strain was 68.0 mol%. DNA-DNA hybridization between strain SAH-A6 T and the most closely related members of the genus Halorubrum were below 55 %, suggesting that the new isolate constitutes a different genospecies. On the bases of chemotaxonomic, phenotypic and genotypic data, strain SAH-A6 T (=KCCM 43215 T =JCM 31519 T ) represents a novel species of the genus Halorubrum, for which the name Halorubrumaethiopicum sp. nov. is proposed.