Halarchaeum salinum sp. nov., a moderately acidophilic haloarchaeon isolated from commercial sea salt

Three halophilic archaeal strains, MH1-34-1T, MH1-16-1 and MH1-224-5 were isolated from commercial salt samples produced from seawater in Indonesia, the Philippines and Japan, respectively. Cells of the three strains were pleomorphic and stained Gram-negative. Strain MH1-34-1T was orange–red pigmented, while MH1-16-1 and MH1-224-5 were pink-pigmented. Strain MH1-34-1T was able to grow at 12–30 % (w/v) NaCl (with optimum at 18 % NaCl, w/v) at pH 4.5–7.2 (optimum, pH 5.2–5.5) and at 15–45 °C (optimum, 42 °C). Strains MH1-16-1 and MH1-224-5 grew in slightly different ranges. These strains required at least 1 mM Mg2+ for growth. The 16S rRNA gene sequences of strains MH1-34-1T, MH1-16-1 and MH1-224-5 were almost identical (99.8–99.9 % similarities), and the closest relative was Halarchaeum acidiphilum MH-1-52-1T with 98.4 % similarities. The DNA G+C contents of MH1-34-1T, MH1-16-1 and MH1-224-5 were 59.3, 60.8 and 61.0 mol%, respectively. The level of DNA–DNA relatedness amongst the three strains was 90–91 %, while that between each of the three strains and Halarchaeum acidiphilum MH1-52-1T was 51–55 %. Based on the phenotypic, genotypic and phylogenetic analyses, it is proposed that the isolates should represent a novel species of the genus Halarchaeum, for which the name Halarchaeum salinum sp. nov. is proposed. The type strain is MH1-34-1T ( = JCM 16330T = CECT 7574T).