Natronoarchaeum rubrum sp. nov., isolated from a marine solar saltern, and emended description of the genus Natronoarchaeum

Salinibaculum litoreum gen. nov., sp. nov., isolated from salted brown alga Laminaria

A novel Gram-stain-negative, aerobic and rod-shaped halophilic archaeon, designated HD8-45T, was isolated from the red brine of salted brown alga Laminaria produced at Dalian, PR China. According to the results of 16S rRNA gene and rpoB' gene sequence comparisons, strain HD8-45T showed the highest sequence similarity to the corresponding genes of Salinirussus salinus YGH44T (95.1 and 85.2 % similarities, respectively), Halovenus aranensis EB27T (91.2 and 86.0 % similarities, respectively). The low sequence similarity and the phylogeny implied the novel generic status of strain HD8-45T. Genomic relatedness analyses showed that strain HD8-45T were clearly distinguished from other species in the order Halobacteriales, with average nucleotide identity, amino acid identity and in silico DNA-DNA hybridization values not more than 75.1, 65.6 and 21.5 %. The polar lipid pattern contained phosphatidylglycerol, phosphatidylglycerol phosphate methyl ester, two major glycolipids and two minor glycolipids. The two major glycolipids and a minor glycolipid were chromatographically identical to disulfated mannosyl glucosyl diether, sulfated mannosyl glucosyl diether and mannosyl glucosyl diether, respectively. The major respiratory quinones were menaquinone MK-8 and MK-8(H2). The DNA G+C content was 62.0 mol% (Tm) and 61.9 mol% (genome). All these results showed that strain HD8-45T represents a novel species of a new genus in the order Halobacteriales, for which the name Salinibaculum litoreum gen. nov., sp. nov. is proposed. The type strain of Salinibaculum litoreum is HD8-45T (=CGMCC 1.15328T=JCM 31107T).

Natronoarchaeum persicum sp. nov., a haloarchaeon isolated from a hypersaline lake

A novel halophilic archaeon, designated strain WIIAL99T, was isolated from Lake Meyghan, a hypersaline lake in Iran. Cells of strain WIIAL99T were non-motile, catalase-positive and oxidase-negative. Strain WIIAL99T required at least 2.5 M NaCl and 0.05 M MgCl2 for growth. Optimal growth was achieved at 3.5 M NaCl and 0.1 M MgCl2. The optimum pH and temperature for growth were pH 7.0 and 37-40 °C; it was able to grow at pH 6.0-8.5 and 20-55 °C. Cells lysed in distilled water and the minimal NaCl concentration to prevent cell lysis was 8 % (w/v). The major polar lipids of strain WIIAL99T were phosphatidylglycerol, phosphatidylglycerol phosphate methyl ester, disulfated diglycosyl diether and one unidentified glycolipid. The DNA G+C content of strain WIIAL99T was 66.7 mol%. The closest relative was Natronoarchaeum rubrum JCM 17119T with 98.2 % similarity in the orthologous 16S rRNA gene sequence. Analysis of 16S rRNA and rpoB' gene sequences indicated that strain WIIAL99T is a member of the genus Natronoarchaeum in the family Halobacteriaceae and forms a distinct cluster. It was concluded that strain WIIAL99T (=IBRC-M 11062T=LMG 29814T) represents a novel species of the genus Natronoarchaeum, for which the name Natronoarchaeum persicum sp. nov. is proposed.

Systematics of haloarchaea and biotechnological potential of their hydrolytic enzymes

Halophilic archaea, also referred to as haloarchaea, dominate hypersaline environments. To survive under such extreme conditions, haloarchaea and their enzymes have evolved to function optimally in environments with high salt concentrations and, sometimes, with extreme pH and temperatures. These features make haloarchaea attractive sources of a wide variety of biotechnological products, such as hydrolytic enzymes, with numerous potential applications in biotechnology. The unique trait of haloarchaeal enzymes, haloenzymes, to sustain activity under hypersaline conditions has extended the range of already-available biocatalysts and industrial processes in which high salt concentrations inhibit the activity of regular enzymes. In addition to their halostable properties, haloenzymes can also withstand other conditions such as extreme pH and temperature. In spite of these benefits, the industrial potential of these natural catalysts remains largely unexplored, with only a few characterized extracellular hydrolases. Because of the applied impact of haloarchaea and their specific ability to live in the presence of high salt concentrations, studies on their systematics have intensified in recent years, identifying many new genera and species. This review summarizes the current status of the haloarchaeal genera and species, and discusses the properties of haloenzymes and their potential industrial applications.

Microbial diversity of the hypersaline and lithium-rich Salar de Uyuni, Bolivia

Salar de Uyuni, situated in the Southwest of the Bolivian Altiplano, is the largest salt flat on Earth. Brines of this athalassohaline hypersaline environment are rich in lithium and boron. Due to the ever- increasing commodity demand, the industrial exploitation of brines for metal recovery from the world's biggest lithium reservoir is likely to increase substantially in the near future. Studies on the composition of halophilic microbial communities in brines of the salar have not been published yet. Here we report for the first time on the prokaryotic diversity of four brine habitats across the salar. The brine is characterized by salinity values between 132 and 177 PSU, slightly acidic to near-neutral pH and lithium and boron concentrations of up to 2.0 and 1.4g/L, respectively. Community analysis was performed after sequencing the V3-V4 region of the 16S rRNA genes employing the Illumina MiSeq technology. The mothur software package was used for sequence processing and data analysis. Metagenomic analysis revealed the occurrence of an exclusively archaeal community comprising 26 halobacterial genera including only recently identified genera like Halapricum, Halorubellus and Salinarchaeum. Despite the high diversity of the halobacteria-dominated community in sample P3 (Shannon-Weaver index H'=3.12 at 3% OTU cutoff) almost 40% of the Halobacteriaceae-assigned sequences could not be classified on the genus level under stringent filtering conditions. Even if the limited taxonomic resolution of the V3-V4 region for halobacteria is considered, it seems likely to discover new, hitherto undescribed genera of the family halobacteriaceae in this particular habitat of Salar de Uyuni in future.