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

A novel extremely halophilic archaeon, designated SAH-A6T, was isolated from a sample of commercial rock salt in Ethiopia. Cells of SAH-A6T 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). Mg2+ was not required for growth of SAH-A6T cells. On the basis of 16S rRNA gene sequence analysis, strain SAH-A6T was closely related to Halorubrum halodurans Cb34T (99.1 %), Halorubrum rubrum YC87T (98.9 %), Halorubrum aquaticum EN-2T (98.7 %), Halorubrum cibi JCM 15757T (98.4 %), Halorubrum luteum CGSA15T (97.3 %), Halorubrum lipolyticum 9-3T (97.1 %), Halorubrum tibetense 8W8T (97.1 %), Halorubrum kocurii JCM 1478T (97.1 %), Halorubrum halophilum B8T (97.0 %) and Halorubrum persicum C49T (97.0 %). Phylogenetic analysis based on the rpoB' gene sequences showed that strain SAH-A6T was closely related to Hrr. halodurans Cb34T (99.7 %), Hrr. aquaticum JCM 14031T (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-A6T 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-A6T (=KCCM 43215T=JCM 31519T) represents a novel species of the genus Halorubrum, for which the name Halorubrumaethiopicum sp. nov. is proposed.