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

A novel extremely halophilic archaeon, designated SAH-A6, was isolated from a sample of commercial rock salt in Ethiopia. Cells of SAH-A6 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 was not required for growth of SAH-A6 cells. On the basis of 16S rRNA gene sequence analysis, strain SAH-A6 was closely related to Halorubrum halodurans Cb34 (99.1 %), Halorubrum rubrum YC87 (98.9 %), Halorubrum aquaticum EN-2 (98.7 %), Halorubrum cibi JCM 15757 (98.4 %), Halorubrum luteum CGSA15 (97.3 %), Halorubrum lipolyticum 9-3 (97.1 %), Halorubrum tibetense 8W8 (97.1 %), Halorubrum kocurii JCM 1478 (97.1 %), Halorubrum halophilum B8 (97.0 %) and Halorubrum persicum C49 (97.0 %). Phylogenetic analysis based on the rpoB' gene sequences showed that strain SAH-A6 was closely related to Hrr. halodurans Cb34 (99.7 %), Hrr. aquaticum JCM 14031 (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 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 (=KCCM 43215=JCM 31519) represents a novel species of the genus Halorubrum, for which the name Halorubrumaethiopicum sp. nov. is proposed.