Halopiger thermotolerans sp nov., a thermo-tolerant haloarchaeon isolated from commercial salt

Three thermo-tolerant halophilic archaeal strains, SR-441(T), SR-412 and SR-188, were isolated from commercial salt samples. Cells were non-motile pleomorphic rod-shaped, and stained Gram-negative. Colonies were pink-pigmented. The three strains were able to grow with 1.7-4.6 M NaCl (optimum, 2.5 M), at pH 6.5-9.0 (optimum, pH 8.0) and at 35-60 degrees C (optimum, 45 degrees C). The orthologous 16S rRNA gene sequence similarities amongst the three strains were 98.899.3%, and the level of DNA DNA relatedness was 71-74 and 72-75% (reciprocally). The closest relative was Halopiger aswanensis JCM 11628(T) with 98.6 %-99.1 % similarity in the orthologous 16S rRNA gene sequences, followed by two more Halopiger species, Halopiger xanaduensis JCM 14033(T) (98.5 %-99.1%) and Halopiger salifodinae JCM 9578(T) (95.5%95.6%). DNA DNA relatednesses between the three strains and H. aswanensis JCM 11628(T) and H. xanaduensis JCM 140331 were 61 and 54%, respectively. The polar lipids of the three novel strains were phosphatidylglycerol, phosphatidylglycerol phosphate methyl ester, and bissulfated diglycosyl archaeol-1. The most distinctive feature of the three strains was the ability to grow at 60 degrees C, while the maximum growth temperature of H. aswanensis is 55 degrees C. Based on phenotypic and phylogenetic analyses, the isolates are considered to represent a novel species of the genus Halopiger, for which the name Halopiger therm otolerans sp. nov. is proposed. The type strain is SR-441(T) (=JCM 19583(T)=KCTC 4248(T)) isolated from solar salt produced in Australia. SR-412 (=JCM 19582) and SR-188 (=JCM 19581) isolated from commercial salt samples are additional strains of the species.