Halorubrum kocurii sp. nov., an archaeon isolated from a saline lake

Roseomonas populi sp. nov., an acetate-degrading bacteria isolated from the stem of Populus tomentosa

Strain CN29T, isolated from the stem of 5- to 6-year-old Populus tomentosa in Shandong, China, was characterized using a polyphasic taxonomic approach. Cells of CN29T were Gram-stain negative, aerobic, nonspore-forming, and nonmotile coccoid. Growth occurred at 20-37 °C, pH 4.0-9.0 (optimum, pH 6.0), and with 0-1% NaCl (optimum, 1%). Phylogenetic analysis based on the 16S rRNA gene sequence indicated that strain CN29T was closely related to members of the genus Roseomonas and closest to Roseomonas pecuniae N75T (96.6%). This classification was further supported by phylogenetic analysis using additional core genes. The average nucleotide identity and digital DNA‒DNA hybridization values between strain CN29T and Roseomonas populi CN29T were 82.7% and 27.8%, respectively. The genome size of strain CN29T was 5.87 Mb, with a G + C content of 70.9%. The major cellular fatty acids included summed feature 8 (C18:1 ω7c/C18:1 ω6c), C19:0 cyclo ω8c and C16:0. The major respiratory quinone was Q-10. The polar lipids were phosphatidylcholine, aminolipid, phosphatidylglycerol, and diphosphatidylglycerol. Strain CN29T can utilize acetate as a carbon source for growth and metabolism. Additionally, it contains acid phosphatase (2-naphthyl phosphate), which catalyzes the hydrolysis of phosphoric monoesters. The CN29T strain contains several genes, including maeB, gdhB, and cysJ, involved in carbon, nitrogen, and sulfur cycling. These findings suggest that the strain may actively participate in ecosystem cycling, leading to soil improvement and promoting the growth of poplar trees. Based on the phylogenetic, phenotypic, and genotypic characteristics, strain CN29T is concluded to represent a novel species of the genus Roseomonas, for which the name Roseomonas populi sp. nov. is proposed. The type strain is CN29T (= JCM 35579T = GDMCC 1.3267T).

The Osmoprotectant Switch of Potassium to Compatible Solutes in an Extremely Halophilic Archaea Halorubrum kocurii 2020YC7

The main osmoadaptive mechanisms of extremely halophilic archaea include the “salt-in” strategy and the “compatible solutes” strategy. Here we report the osmoadaptive mechanism of an extremely halophilic archaea H. kocurii 2020YC7, isolated from a high salt environment sample. Genomic data revealed that strain 2020YC7 harbors genes trkA, trkH, kch for K⁺ uptake, kefB for K⁺ output, treS for trehalose production from polysaccharide, and betaine/carnitine/choline transporter family gene for glycine betaine uptake. Strain 2020YC7 could accumulate 8.17 to 28.67 μmol/mg protein K⁺ in a defined medium, with its content increasing along with the increasing salinity from 100 to 200 g/L. When exogenous glycine betaine was added, glycine betaine functioned as the primary osmotic solute between 200 and 250 g/L NaCl, which was accumulated up to 15.27 mg/mg protein in 2020YC7 cells. RT-qPCR results completely confirmed these results. Notably, the concentrations of intracellular trehalose decreased from 5.26 to 2.61 mg/mg protein as the NaCl increased from 50 to 250 g/L. In combination with this result, the transcript level of gene treS, which catalyzes the production of trehalose from polysaccharide, was significantly up-regulated at 50–100 g/L NaCl. Therefore, trehalose does not act as an osmotic solute at high NaCl concentrations (more than 100 g/L) but at relatively low NaCl concentrations (50–100 g/L). And we propose that the degradation of cell wall polysaccharide, as a source of trehalose in a low-salt environment, may be one of the reasons for the obligate halophilic characteristics of strain 2020YC7.

Halalkalirubrum salinum gen. nov., sp. nov., a halophilic archaeon isolated from a saline lake

A novel extremely halophilic archaeon, strain N1521^T, was isolated from a saline lake in Tibet, China. Cells of the strain were pleomorphic and Gram-stain-negative. It produced red pigments. Growth was observed at 4-42 °C (optimum, 37 °C), pH 7.0-10.5 (optimum, 8.0-9.5), NaCl 11%-25% (optimum, 15%) and in the presence of 0-0.1 M MgCl₂ (optimum, 0.05 M) in aerobic conditions. The minimum NaCl concentration that prevented cell lysis was 2% (w/v). The major polar lipids of strain N1521^T were phosphatidylglycerol sulfate, phosphatidylglycerol phosphate methyl ester, phosphatidylglycerol and an unidentified glycolipid. The DNA G + C content was 58.37 mol%. According to 16S rRNA gene sequence comparisons, strain N1521^T revealed the highest sequence similarity to Haloprofundus halophilus NK23^T (91.38%) and Halogranum amylolyticum TNN58^T (91.00%), and low sequence similarities (< 91%) with other genera in the order Haloferacales. Phylogenetic analysis based on the 16S rRNA gene and rpoB' gene sequence showed that strain N1521^T was distinct from the members of the order Haloferacales. The digital DNA-DNA hybridization, average nucleotide identity and average amino acid identity values calculated from whole genome-sequence comparison between strain N1521^T and the members of the order Haloferacales were in the ranges of 15.1-18.2%, 68.8-73.0%, and 58.4-63.9%, respectively. Phylogenetic tree reconstructions based on the whole-genome sequences revealed that strain N1521^T was closer to the members of the family Halorubraceae. Based on the data obtained, strain N1521^T is thus considered to represent a novel species of a new genus within the family Halorubraceae, for which the name Halalkalirubrum salinum gen. nov., sp. nov. is proposed. The type strain is N1521^T (= CGMCC 1.16693 = JCM 33785).

Halorubrum amylolyticum sp. nov., a novel halophilic archaeon isolated from a salt mine

A pleomorphic and non-motile halophilic archaeon forming light-red pigmented colonies, strain ZC67^T, was isolated from the Yuanyongjing Salt Mine, Yunnan, China. Based on similarity search and phylogenetic analysis of the 16S rRNA gene sequence, strain ZC67^T belongs to the genus Halorubrum and is closely related to the species of Halorubrum (Hrr.) saccharovorum JCM 8865^T, Hrr. persicum C49^T, Hrr. halophilum B8^T, Hrr. lipolyticum 9-3^T, Hrr. salsamenti Y69^T and Hrr. depositum Y78^T with 16S rRNA gene sequence similarities of 99.0%, 98.7%, 98.5%, 98.4%, 98.1% and 97.7%, respectively. The values of average nucleotide identity (ANI) and average amino-acid identity (AAI) between strain ZC67^T and its close relatives were less than 90.5% and 89.3%, respectively. In silico DNA-DNA hybridization (DDH) analysis showed that DNA-DNA relatedness between strain ZC67^T and its relatives is less than 45%. Values of ANI, AAI and in silico DDH were clearly below the thresholds used for the delineation of a new species. The major polar lipids of strain ZC67^T were similar to other neutrophilic members in the genus Halorubrum containing phosphatidylglycerol, phosphatidylglycerolphosphate methyl ester, phosphatidylglycerol sulfate and sulfated mannosyl-glucosyl-glycerol diether-1. The DNA G+C content was determined to be 66.3 mol% (based on the draft genome). Combined with other diagnostic characteristics, e.g. phenotypic and chemotaxonomic differences, strain ZC67^T is concluded to represent a novel species in the genus Halorubrum, for which the name Halorubrum amylolyticum sp. nov. is proposed. The type strain is ZC67^T (=CGMCC 1.15718^T = JCM 31850^T).

Halorubrum salsamenti sp. nov., a Novel Halophilic Archaeon Isolated from a Brine of Salt Mine

A non-motile, spherical or oval extremely halophilic archaeon, strain Y69^T, was isolated from a brine of the Yunnan salt mine, China. Colonies on JCM 168 agar plate were round (1-2 mm in diameter), moist, and orange-pigmented. Phylogenetic analysis of the almost-complete 16S rRNA gene sequence showed that the isolate belonged to the species of the genus Halorubrum, with a close relationship to Halorubrum aidingense 31-hong^T (98.5%), Halorubrum lacusprofundi ATCC 49239^T (98.2%), and Halorubrum kocurii BG-1^T (98.0%). The major polar lipids of strain Y69^T were phosphatidylglycerol phosphate methyl ester, phosphatidylglycerol sulfate and a sulfated diglycosyl diether. Strain Y69^T grew in 15-30% (w/v) NaCl. The temperature and pH ranges for growth were 25-50 °C and 6.5-9.0, respectively. Optimal growth occurred at 20% (w/v) NaCl, 42 °C, and pH 8.0. Mg²⁺ was required for growth. The DNA G+C content was determined to be 65.1 mol% by the thermal denaturation method. DNA-DNA hybridization values between strain Y69^T and the closely related species were lower than 70%. Based on the data presented in this study, strain Y69^T represents a novel species for which the name Halorubrum salsamenti sp. nov. is proposed. The type of the strain is Y69^T (=CGMCC 1.15455^T = JCM 31270^T).

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.

Haloparvum sedimenti gen. nov., sp. nov., a member of the family Haloferacaceae

Two extremely halophilic archaeal strains, DYS4T and Y2, were isolated from rock salt of the Jiangcheng Salt Mine, Yunnan province, China. Cells of the two strains were non-motile, pleomorphic rods and Gram-stain-negative. The cells produced light red-pigmented colonies. Strains DYS4T and Y2 required 2.6-3.4 M NaCl, pH 7.5- 8.0 and 42 ºC in aerobic conditions for optimal growth. Mg2+ was required for growth. The major polar lipids of both strains were phosphatidylglycerol, phosphatidylglycerol phosphate methyl ester, phosphatidylglycerol sulfate and sulfated mannosyl glucosyl diether. An unidentified minor glycolipid spot was present for strains DYS4T and Y2, which differentiates them from the closely related species of the genera Halorubrum and Halopenitus. The lipid core of the glycolipid was sn-2,3-diphytanylglycerol (C20C20). The sequence similarity of the 16S rRNA gene demonstrated that the closest relatives of strains DYS4T and Y2 were Halorubrum aidingense 31-hongT (94.1 % and 93.6 % 16S rRNA gene sequence similarity to DYS4T and Y2, respectively) and Halopenitus salinus SKJ47T (93.4% and 93.1%). Phylogenetic analysis of the 16S rRNA gene and the rpoB' gene revealed that strains DYS4T and Y2 formed an independent lineage closely related to the genera Halorubrum and Halopenitus. The DNA G+C contents of strains DYS4T and Y2 were 68.2 and 67.0 mol%, respectively. The DNA-DNA relatedness value between strains DYS4T and Y2 was 90.0 ± 0.5%, while that between strain DYS4T and other closest relatives was less than 26 % (19 ± 0.7 % for Halorubrum aidingense 31-hongT and 25 ± 0.3% for Halopenitus salinus SKJ47T). The phenotypic, chemotaxonomic and phylogenetic properties suggest that strains DYS4T and Y2 (=CGMCC 1.15000=JCM 30892) represent a novel species of a new genus within the family Haloferacaceae, for which the name Haloparvum sedimenti gen. nov., sp. nov. is proposed. The type strain of the type species is DYS4T (=CGMCC 1.14998T=JCM 30891T).

Halorubrum yunnanense sp. nov., isolated from a subterranean salt mine

Two halophilic archaeal strains, Q85T and Q86, were isolated from a subterranean salt mine in Yunnan, China. Cells were rod-shaped, Gram-stain-negative and motile. Colonies were red, smooth, convex and round (1.0–2.0 mm in diameter). The orthologous 16S rRNA and rpoB′ gene sequences of these two strains were almost identical (99.5 and 99.7 % similarities). Their closest relatives were Halorubrum kocurii BG-1T (98.0–98.1 % 16S rRNA gene sequence similarity), Halorubrum aidingense 31-hongT (97.6–97.7 %) and Halorubrum lipolyticum 9-3T (97.5–97.6 %). The level of DNA–DNA relatedness between strains Q85T and Q86 was 90 %, while that between Q85T and other related Halorubrum strains was less than 30 % (29 % for H. kocurii BG-1T, 25 % for H. aidingense 31-hongT and 22 % for H. lipolyticum 9-3T). Optimal growth of the two novel strains was observed with 20 % (w/v) NaCl and at 42–45 °C under aerobic conditions, with a slight difference in optimum Mg2+ concentration (0.7 M for Q85T, 0.5 M for Q86) and a notable difference in optimum pH (pH 7.5 for Q85T, pH 6.6 for Q86). Anaerobic growth occurred with nitrate, but not with l-arginine or DMSO. The major polar lipids of the two strains were identical, including phosphatidylglycerol, phosphatidylglycerol phosphate methyl ester, phosphatidylglycerol sulfate and sulfated diglycosyl diether, which are the major lipids of the genus Halorubrum. The G+C contents of strains Q85T and Q86 were 66.3 and 66.8 %, respectively. Based on the phenotypic, chemotaxonomic and phylogenetic properties of strains Q85T and Q86, a novel species, Halorubrum yunnanense sp. nov., is proposed. The type strain is Q85T ( = CGMCC 1.15057T = JCM 30665T).

Halorubrum halodurans sp. nov., an extremely halophilic archaeon isolated from a hypersaline lake

Two extremely halophilic archaea, strains Cb34T and C170, belonging to the genus Halorubrum, were isolated from the brine of the hypersaline lake Aran-Bidgol in Iran. Cells of the two strains were motile, pleomorphic rods, stained Gram-variable and produced red-pigmented colonies. Strains Cb34T and C170 required 25 % (w/v) salts, pH 7.0 and 37 °C for optimal growth under aerobic conditions; 0.3 M Mg2+ was required. Cells of both isolates were lysed in distilled water and hypotonic treatment with < 10 % NaCl provoked cell lysis. Phylogenetic analysis based on 16S rRNA gene sequence similarities showed that these two strains were closely related to Halorubrum cibi B31T (98.8 %) and other members of the genus Halorubrum. In addition, studies based on the rpoB' gene revealed that strains Cb34T and C170 are placed among the species of Halorubrum and are closely related to Halorubrum cibi B31T, with rpoB' gene sequence similarity less than or equal to 95.7 %. The polar lipid patterns of both strains consisted of phosphatidylglycerol, phosphatidylglycerol phosphate methyl ester, phosphatidylglycerol sulfate and sulfated mannosyl glucosyl diether. The DNA G+C content was 62.1-62.4 mol%. DNA-DNA hybridization studies confirmed that strains Cb34T and C170 constitute a distinct species. Data obtained in this study show that the two strains represent a novel species, for which the name Halorubrum halodurans sp. nov. is proposed. The type strain is Cb34T ( = CECT 8745T = IBRC-M 10233T).

Halorubrum rutilum sp. nov. isolated from a marine solar saltern

A halophilic archaeal strain, YJ-18-S1(T), was isolated from Yangjiang marine solar saltern, Guangxi Province, China. Cells were pleomorphic, stained Gram-negative and formed red-pigmented colonies on agar plates. Strain YJ-18-S1(T) was able to grow at 20-55 °C (optimum 37 °C), at 0.9-4.8 M NaCl (optimum 2.6 M NaCl), at 0.005-1.0 M MgCl2 (optimum 0.3 MgCl2) and at pH 5.5-8.5 (optimum pH 7.0). The cells were lysed in distilled water, and the minimal NaCl concentration to prevent cell lysis was found to be 5 % (w/v). The major polar lipids of the strain were phosphatidic acid, phosphatidylglycerol, phosphatidylglycerol phosphate methyl ester, phosphatidylglycerol sulfate and sulfated mannosyl glucosyl diether. The 16S rRNA gene and rpoB' gene of strain YJ-18-S1(T) were phylogenetically related to the corresponding genes of Halorubrum members (94.3-98.0 and 86.7-96.1 % similarities, respectively). The DNA G+C content of strain YJ-18-S1(T) was 66.2 mol%. The phenotypic, chemotaxonomic and phylogenetic properties suggested that strain YJ-18-S1(T) (=CGMCC 1.12554(T) = JCM 30030(T)) represents a new species of Halorubrum, for which the name Halorubrum rutilum sp. nov. is proposed.

Halorubrum persicum sp. nov., an extremely halophilic archaeon isolated from sediment of a hypersaline lake

An extremely halophilic archaeon belonging to the genus Halorubrum, strain C49T, was isolated from sediment of the hypersaline lake Aran-Bidgol in Iran. Phylogenetic analysis based on 16S rRNA gene sequence similarities showed that strain C49T was closely related to Halorubrum saccharovorum JCM 8865T (99.5 %) and other species of the genus Halorubrum. Studies based on multilocus sequence analysis revealed that strain C49T is placed among the species of Halorubrum; the strain constituted a defined branch in comparison with the type strains of species of Halorubrum, while the 16S rRNA gene sequence divergence could not define the status of the newly isolated strain. For optimum growth, strain C49T required 20 % (w/v) salts at pH 7.0 and 37 °C under aerobic conditions. Mg2+ was not required. The cells were pleomorphic rods, motile and stained Gram-variable. Colonies of the strain were pink. Hypotonic treatment with <12 % NaCl provoked cell lysis. The polar lipid pattern of strain C49T consisted of phosphatidylglycerol, phosphatidylglycerol phosphate methyl ester derived from both C20C20 and C20C25 archaeol, phosphatidylglycerol sulfate and sulfated mannosyl glucosyl diether. The DNA G+C content was 64.2 mol%. DNA-DNA hybridization studies and average nucleotide identity confirmed that strain C49T constitutes a distinct genospecies. Data obtained in this study show that strain C49T represents a novel species, for which the name Halorubrum persicum sp. nov. is proposed. The type strain is C49T ( = IBRC-M 10232T = JCM 30541T).

Evolutionary aspects of lipoxygenases and genetic diversity of human leukotriene signaling

Leukotrienes are pro-inflammatory lipid mediators, which are biosynthesized via the lipoxygenase pathway of the arachidonic acid cascade. Lipoxygenases form a family of lipid peroxidizing enzymes and human lipoxygenase isoforms have been implicated in the pathogenesis of inflammatory, hyperproliferative (cancer) and neurodegenerative diseases. Lipoxygenases are not restricted to humans but also occur in a large number of pro- and eucaryotic organisms. Lipoxygenase-like sequences have been identified in the three domains of life (bacteria, archaea, eucarya) but because of lacking functional data the occurrence of catalytically active lipoxygenases in archaea still remains an open question. Although the physiological and/or pathophysiological functions of various lipoxygenase isoforms have been studied throughout the last three decades there is no unifying concept for the biological importance of these enzymes. In this review we are summarizing the current knowledge on the distribution of lipoxygenases in living single and multicellular organisms with particular emphasis to higher vertebrates and will also focus on the genetic diversity of enzymes and receptors involved in human leukotriene signaling.

Phages in nature

Bacteriophages or phages are the most abundant organisms in the biosphere and they are a ubiquitous feature of prokaryotic existence. A bacteriophage is a virus which infects a bacterium. Archaea are also infected by viruses, whether these should be referred to as 'phages' is debatable, but they are included as such in the scope this article. Phages have been of interest to scientists as tools to understand fundamental molecular biology, as vectors of horizontal gene transfer and drivers of bacterial evolution, as sources of diagnostic and genetic tools and as novel therapeutic agents. Unraveling the biology of phages and their relationship with their hosts is key to understanding microbial systems and their exploitation. In this article we describe the roles of phages in different host systems and show how modeling, microscopy, isolation, genomic and metagenomic based approaches have come together to provide unparalleled insights into these small but vital constituents of the microbial world.

Halorubrum halophilum sp. nov., an extremely halophilic archaeon isolated from a salt-fermented seafood

A novel, red-pigmented, pleomorphic and short rod-shaped haloarchaeon, designated B8(T), was isolated from a salt-fermented seafood. Strain B8(T) was found to be able to grow at 20-45 °C, in the presence of 15-30 % (w/v) NaCl and at pH 7.0-9.0. The optimum requirements were found to be a temperature range of 35-40 °C, pH 8.0 and the presence of 25 % NaCl. The cells of strain B8(T) were observed to be Gram-staining negative and lysed in distilled water. Anaerobic growth did not occur in the presence of nitrate, L-arginine, dimethyl sulfoxide or trimethylamine N-oxide. The catalase and oxidase activities were found to be positive and nitrate was reduced in aerobic conditions. Tween 20, 40 and 80 were found to be hydrolyzed, whereas casein, gelatin and starch were not hydrolyzed. Indole or H2S was not formed and urease activity was not detected. A phylogenetic analysis based on the 16S rRNA gene sequences indicated that strain B8(T) is most closely related to members of the genus Halorubrum in the family Halobacteriaceae. Strain B8(T) was found to have three 16S rRNA genes, rrnA, rrnB and rrnC; similarities between the 16S rRNA gene sequences are 99.0-99.8 %. Strain B8(T) shared 99.0 % 16S rRNA gene sequence similarity with Halorubrum (Hrr.) lipolyticum JCM 13559(T) and Hrr. saccharovorum DSM 1137(T), 98.8 % with Hrr. kocurii JCM 14978(T), 98.3 % with Hrr. lacusprofundi DSM 5036(T), 98.0 % with Hrr. arcis JCM 13916(T), 97.7 % with Hrr. aidingense JCM 13560(T) and 97.0 % with Hrr. aquaticum JCM 14031(T), as well as 93.7-96.5 % with other type strains in the genus Halorubrum. The RNA polymerase subunit B' gene sequence similarity of strain B8(T) with Hrr. kocurii JCM 14978(T) is 97.2 % and lower with other members of the genus Halorubrum. DNA-DNA hybridization experiments showed that strain B8(T) shared equal or lower than 50 % relatedness with reference species in the genus Halorubrum. The genomic DNA G+C content of strain B8(T) was determined to be 64.6 mol%. The major isoprenoid quinone of strain B8(T) was identified as menaquinone-8 and the major polar lipids as phosphatidylglycerol, phosphatidylglycerol phosphate methyl ester, phosphatidylglycerol sulfate, sulfated mannosyl glucosyl diether and an unidentified phospholipid. Based on this polyphasic taxonomic study, strain B8(T) is considered to represent a new species in the genus Halorubrum, for which the name Hrr. halophilum sp. nov. is proposed. The type strain is B8(T) (=JCM 18963(T) = CECT 8278(T)).

Halobellus rarus sp. nov., a halophilic archaeon from an inland salt lake of China

Two halophilic archaeal strains, YC21(T) and YC77, were isolated from an inland salt lake of China. Both have pleomorphic rod-shaped cells that lyse in distilled water, stain Gram-negative and form red-pigmented colonies. They are neutrophilic, require at least 2.1 M NaCl for growth under the optimum growth temperature of 37 °C. The major polar lipids of the two strains were phosphatidylglycerol (PG), phosphatidylglycerol phosphate methyl ester (PGP-Me), phosphatidylglycerol sulfate (PGS), two major glycolipids (GL1 and GL2) chromatographically identical to sulfated mannosyl glucosyl diether (S-DGD-1) and mannosyl glucosyl diether (DGD-1), respectively. Trace amounts of two unidentified lipids (GL0-1 and GL0-2) were also detected. The 16S rRNA gene sequences of the two strains are 99.9 % identical, show 94.0-98.9 % similarity to the closest relative members of Halobellus of the family Halobacteriaceae. The rpoB' gene similarity between strains YC21(T) and YC77 is 99.8 % and show 90.3-95.3 % similarity to the closest relative members of Halobellus. The DNA G+C content of strains YC21(T) and YC77 were 66.1 and 66.2 mol%, respectively. The DNA-DNA hybridization value between strain YC20(T) and strain YC77 was 89 %, and the two strains showed low DNA-DNA relatedness with Halobellus limi TBN53(T), the most related member of Halobellus. The phenotypic, chemotaxonomic and phylogenetic properties suggest that strains YC21(T) and YC77 represent a novel species of the genus Halobellus, for which the name Halobellus rarus sp. nov. is proposed. The type strain is YC21(T) (=CGMCC 1.12121(T) = JCM 18362(T)).

Characterization of Halorubrum sfaxense sp. nov., a New Halophilic Archaeon Isolated from the Solar Saltern of Sfax in Tunisia

An extremely halophilic archaeon, strain ETD6, was isolated from a marine solar saltern in Sfax, Tunisia. Analysis of the 16S rRNA gene sequence showed that the isolate was phylogenetically related to species of the genus Halorubrum among the family Halobacteriaceae, with a close relationship to Hrr. xinjiangense (99.77% of identity). However, value for DNA-DNA hybridization between strain ETD6 and Hrr.xinjiangense were about 24.5%. The G+C content of the genomic DNA was 65.1 mol% (T(m)). Strain ETD6 grew in 15-35% (w/v) NaCl. The temperature and pH ranges for growth were 20-55°C and 6-9, respectively. Optimal growth occurred at 25% NaCl, 37°C, and pH 7.4. The results of the DNA hybridization against Hrr. xinjiangense and physiological and biochemical tests allowed genotypic and phenotypic differentiation of strain ETD6 from other Hrr. species. Therefore, strain ETD6 represents a novel species of the genus Halorubrum, for which the name Hrr. sfaxense sp. nov. is proposed. The Genbank EMBL-EBI accession number is GU724599.

Halorubrum aquaticum sp. nov., an archaeon isolated from hypersaline lakes

Two halophilic archaea, strains EN-2T and SH-4, were isolated from the saline lakes Erliannor and Shangmatala, respectively, in Inner Mongolia, China. Cells were strictly aerobic, motile rods. Colonies were red. Strains EN-2T and SH-4 were able to grow at 25–50 °C (optimum 35–40 °C), with 2.5–5.0 M NaCl (optimum 3.4 M NaCl) and at pH 6.0–9.0 (optimum pH 7.5). MgCl2 was not required for growth. Cells lysed in distilled water and the lowest NaCl concentration that prevented cell lysis was 12 % (w/v). On the basis of 16S rRNA gene sequence analysis, strains EN-2T and SH-4 were closely related to Halorubrum cibi B31T (97.9 and 98.0 % similarity, respectively), Hrr. tibetense 8W8T (97.3 and 97.7 %), Hrr. alkaliphilum DZ-1T (96.8 and 97.1 %), Hrr. luteum CGSA15T (96.8 and 97.0 %) and Hrr. lipolyticum 9-3T (96.8 and 97.0 %). DNA–DNA hybridization showed that strains EN-2T and SH-4 did not belong to the same species as any of these strains (≤45 % DNA–DNA relatedness) but that they are members of the same species (>70 % DNA–DNA relatedness). Polar lipid analysis revealed that strains EN-2T and SH-4 contained phosphatidylglycerol, phosphatidylglycerol phosphate methyl ester, sulfated diglycosyl diethers and several unidentified glycolipids. The DNA G+C content of both isolates was 62.1 mol%. It was concluded that strains EN-2T and SH-4 represent a novel species of the genus Halorubrum, for which the name Halorubrum aquaticum sp. nov. is proposed. The type strain is EN-2T ( = CECT 7174T  = CGMCC 1.6377T  = JCM 14031T).

Metagenomics and recovery of enzyme genes from alkaline saline environments

Enzymes functioning at alkaline pH are widely used in the detergent industry as additives to improve the stain removal properties of domestic and industrial cleaning products. This industry provides by far the major mass market for enzymes. With constantly changing formulations in detergents and concerns over energy demands, new and improved enzymes are constantly in demand. Soda lakes host dense populations of alkali-loving microbes and, as such, provide vast reservoirs of potentially useful enzymes for such an industry. Traditional recovery methods for new enzymes have involved the isolation of microbes, preferably from a compatible chemical environment such as a soda lake, followed by screening of the isolates for useful enzymic activity. At least two commercially significant enzymes originating from soda lake microbes have been marketed following this route. However, the failure to cultivate more than a small percentage of microbes from most environments necessarily markedly reduces the recovery of new enzymes. In recent years, interest has focussed on more comprehensive recovery methods based around detecting appropriate enzyme genes in nucleic acids extracted from potentially useful sites, thus maximizing coverage of the whole genetic resource in a particular biotope. Here we review progress to date in soda lake biotopes and discuss ways the field may develop in the future.