Haloplanus

Abstract: The Dead Sea, on the border between Israel and Jordan, currently contains around 348 g salt L−1. Divalent cations (Mg2+, Ca2+) dominate over monovalent cations (Na+, K+), while Cl− and Br− are the main anions. The pH of the Sea is about 6. The water balance of the lake is negative, having dropped over 1 m year−1 over the past decade. The water is supersaturated with Na+, with massive quantities of halite precipitating to the bottom of the lake. Biological monitoring since 1980 has indicated that blooms of the unicellular green alga Dunaliella and halophilic Archaea of the family Halobacteriaceae only develop following significant dilution of the upper water layers in the lake after very rainy winters. Such events occurred in 1980, and even more dramatically in 1992, when up to 3.5 × 107 Archaea mL−1 in the diluted upper 5–10 m of the water column coloured the lake red. Species isolated from the lake include Haloferax volcanii, Haloarcula marismortui, Halorubrum sodomense and Halobaculum gomorrense. Dunaliella was no longer observed in the lake after 1996, with prokaryote numbers remaining low. To characterize the residual microbial community in the lake, biomass was collected in February 2007 for environmental genomic analyses. The results were compared with the metagenome of microbial bloom material collected in 1992. The 16S rRNA archaeal phylotypes recovered from the 2007 sample were diverse, with phylotypes distantly related to the genera Halorhabdus, Haloplanus, Natronomonas and others. Halorhabdus sp. also was recovered in culture. The 1992 bloom sample was very homogeneous, however, with a single cluster remotely related to Halobacterium salinarum. These results illustrate that the microbial communities are dynamic, even in one of the most extreme environments on Earth, and exhibit strong shifts in species composition as conditions for life become increasingly adverse.

Abstract: An extremely halophilic archaeon, strain RO5-8T, was isolated from a disused marine solar saltern in China. The cells were pleomorphic and flat. In static liquid medium, cells floated to the surface. Strain RO5-8T stained Gram-negative and colonies were pink-pigmented. It was able to grow at 30–50 °C (optimum 40 °C), at 2.6–4.3 M NaCl (optimum 3.1 M NaCl), at 0.03–0.5 M MgCl2 (optimum 0.03 M MgCl2) and at pH 5.5–7.5 (optimum pH 6.0–6.5). Cells lysed in distilled water and the minimal NaCl concentration to prevent cell lysis was 12 % (w/v). The major polar lipids of strain RO5-8T were phosphatidylglycerol, phosphatidylglycerol phosphate methyl ester, phosphatidylglycerol sulfate and one major glycolipid chromatographically identical to the sulfated mannosyl glucosyl diether S-DGD-1. On the basis of 16S rRNA gene sequence analysis, strain RO5-8T was closely related to three strains of Haloplanus natans with similarities of 97.3–97.6 %. The DNA G+C content of strain RO5-8T was 62.1 mol%. The DNA–DNA hybridization value between strain RO5-8T and Haloplanus natans JCM 14081T was 51.6 %. It was concluded that strain RO5-8T represents a novel species of the genus Haloplanus, for which the name Haloplanus vescus sp. nov. is proposed. The type strain is RO5-8T (=CGMCC 1.8712T =JCM 16055T).

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.

Abstract: Halophilic archaeal strain TBN37T was isolated from Taibei marine solar saltern near Lianyungang city of Jiangsu province, China. Cells were pleomorphic, flat and contained gas vesicles. Cells of strain TBN37T stained Gram-negative and the colonies were pink-pigmented. The strain was able to grow at 25–50 °C (optimum, 37–40 °C), with 1.4–5.1 M NaCl (optimum, 2.1 M NaCl), with 0–1.0 M MgCl2 (optimum, 0.01 M MgCl2) and at pH 6.0–9.0 (optimum, pH 7.5). Cells lysed in distilled water and the minimal NaCl concentration to prevent cell lysis was 8 % (w/v). The major polar lipids of strain TBN37T were phosphatidylglycerol, phosphatidylglycerol phosphate methyl ester, phosphatidylglycerol sulfate and one major glycolipid chromatographically identical to sulfated mannosyl glucosyl diether (S-DGD-1). On the basis of 16S rRNA gene sequence analysis, strain TBN37T was closely related to Haloplanus natans and Haloplanus vescus, with the same similarity of 97.4 %. The DNA G+C content of strain TBN37T is 64.1 mol%. DNA–DNA hybridization values between strain TBN37T and Haloplanus natans JCM 14081T and between strain TBN37T and Haloplanus vescus RO5-8T were 37.6 % and 42.1 %, respectively. It was concluded that strain TBN37T represents a novel species of the genus Haloplanus, for which the name Haloplanus aerogenes sp. nov. is proposed. The type strain is TBN37T ( = CGMCC 1.10124T = JCM 16430T).