Haloplanus litoreus sp. nov. and Haloplanus ruber sp. nov., from a marine solar saltern and an aquaculture farm, respectively

Abstract

Two halophilic archaea, strains GX21(T) and R35(T), were isolated from a marine solar saltern and an aquaculture farm in China, respectively. Cells of the two strains were observed to be pleomorphic, flat, to contain gas vesicles, stain Gram-negative and produce red-pigmented colonies. Strain GX21(T) was found to be able to grow at 25-50 °C (optimum 37 °C), at 2.6-4.8 M NaCl (optimum 3.4 M NaCl), at 0.05-1.0 M MgCl2 (optimum 0.1 M MgCl2) and at pH 6.0-8.5 (optimum pH 6.5) while strain R35(T) was found to be able to grow at 25-45 °C (optimum 37 °C), at 2.1-4.8 M NaCl (optimum 3.1 M NaCl), at 0-0.7 M MgCl2 (optimum 0.03 M MgCl2) and at pH 5.5-9.5 (optimum pH 6.5-7.0). The cells of both isolates were observed to lyse in distilled water. The minimum NaCl concentrations that prevented cell lysis were determined to be 15 % (w/v) for strain GX21(T) and 12 % (w/v) for strain R35(T). The major polar lipids of the two strains were identified as phosphatidylglycerol, phosphatidylglycerol phosphate methyl ester, phosphatidylglycerol sulfate, one major glycolipid and a minor lipid chromatographically identical to sulfated mannosyl glucosyl diether and mannosyl glucosyl diether, respectively. 16S rRNA gene sequence analysis revealed that strains GX21(T) and R35(T) show 97.1 % sequence similarity to each other and are closely related to Haloplanus aerogenes TBN37(T) (96.8 and 95.8 %), Haloplanus vescus RO5-8(T) (96.7 and 96.1 %), Haloplanus salinus YGH66(T) (96.4 and 95.8 %) and Haloplanus natans JCM 14081(T) (96.3 and 95.4 %). The rpoB' gene similarity between strains GX21(T) and R35(T) is 90.5 % and show 88.5-90.8 % similarity to the Haloplanus species with validly published names. The DNA G+C content of strain GX21(T) and R35(T) were determined to be 65.8 and 66.0 mol%, respectively. The DNA-DNA hybridization values between strain GX21(T) and strain R35(T), and the two strains with the Haloplanus species with validly published names, showed less than 50 % DNA-DNA relatedness. It was concluded that strain GX21(T) (=CGMCC 1.10456(T) = JCM 17092(T)) and strain R35(T) (=CGMCC 1.10594 (T) = JCM 17271(T)) represent two new species of Haloplanus, for which the names Haloplanus litoreus sp. nov. and Haloplanus ruber sp. nov. are proposed.