Halosimplex pelagicum sp. nov. and Halosimplex rubrum sp. nov., isolated from salted brown alga Laminaria, and emended description of the genus Halosimplex

Abstract

Two halophilic archaeal strains, R2T and R27T, were isolated from the brown alga Laminaria produced at Dalian, Liaoning Province, China. Both had pleomorphic cells that lysed in distilled water, stained Gram-negative and formed red-pigmented colonies. They grew optimally at 42 °C, pH 7.0 and in the presence of 3.1–3.4 M NaCl and 0.03–0.5 M Mg2+. The major polar lipids of the two strains were phosphatidylglycerol (PG), phosphatidylglycerol phosphate methyl ester (PGP-Me) and four major glycolipids chromatographically identical to those of Halosimplex carlsbadense JCM 11222T. 16S rRNA gene analysis revealed that each strain had two dissimilar 16S rRNA genes and both strains were phylogenetically related to Halosimplex carlsbadense JCM 11222T (92.7–98.8 % similarities). The rpoB′ gene similarities between strains R2T and R27T and between these strains and Halosimplex carlsbadense JCM 11222T were 95.7 %, 96.1 % and 95.8 %, respectively. The DNA G+C contents of strains R2T and R27T were 62.5 mol% and 64.0 mol%, respectively. The DNA–DNA hybridization values between strains R2T and R27T and between the two strains and Halosimplex carlsbadense JCM 11222T were 43 %, 52 % and 47 %, respectively. It was concluded that strain R2T ( = CGMCC 1.10586T = JCM 17263T) and strain R27T ( = CGMCC 1.10591T = JCM 17268T) represent two novel species of the genus Halosimplex , for which the names Halosimplex pelagicum sp. nov. and Halosimplex rubrum sp. nov. are proposed. An emended description of the genus Halosimplex is also presented.