Halorubrum laminariae sp. nov., isolated from the brine of salted brown alga Laminaria.

Abstract

Two halophilic archaeal strains, R60(T) and R61, were isolated from the brine of salted brown alga Laminaria. Cells of the two strains were observed to be rod-shaped, stain Gram-negative and to lyse in distilled water. Strain R60(T) was found to contain gas vacuoles and to produce pink-pigmented colonies, while strain R61 lacked gas vacuoles and produces red-pigmented colonies. Both strains were found to be able to grow at 20-50°C (optimum 30°C), at 1.7-4.8M NaCl (optimum 2.6-3.1M NaCl), at 0-1.0M MgCl2 (optimum 0.005-0.1M MgCl2) and at pH 6.0-9.5 (optimum pH 7.0). The major polar lipids were identified as phosphatidylglycerol, phosphatidylglycerol phosphate methyl ester, phosphatidylglycerol sulfate and one major glycolipid chromatographically identical to a sulfated mannosyl glucosyl diether produced by Halorubrum members of the Halobacteriaceae. The 16S rRNA gene sequences of the two strains were 99.9% identical, showing 94.6-98.0% similarity to those of members of the genus Halorubrum. The EF-2 gene similarity between strains R60(T) and R60 was 100 % and showed 84.6-94.5 % similarity to those of members of the genus Halorubrum. The DNA G+C contents of the two strains were determined to be 63.0mol%. The DNA-DNA hybridization value between strain R60(T) and strain R61 was 92% and the two strains showed low DNA-DNA relatedness with the most related members of Halorubrum. The phenotypic, chemotaxonomic and phylogenetic properties suggest that strain R60(T) (=CGMCC 1.12689(T)=JCM 30040(T)) and strain R61 (=CGMCC 1.12696) represent a novel species of the genus Halorubrum, for which the name Halorubrum laminariae sp. nov. is proposed.