Haloterrigena saccharevitans sp. nov., an extremely halophilic archaeon from Xin-Jiang, China

Characterization of Two Na+(K+, Li+)/H+ Antiporters from Natronorubrum daqingense

The Na⁺/H⁺ antiporter NhaC family protein is a kind of Na⁺/H⁺ exchanger from the ion transporter (IT) superfamily, which has mainly been identified in the halophilic bacteria of Bacillus. However, little is known about the Na⁺/H⁺ antiporter NhaC family of proteins in the extremely halophilic archaea. In this study, two Na⁺/H⁺ antiporter genes, nhaC1 and nhaC2, were screened from the genome of Natronorubrum daqingense based on the gene library and complementation of salt-sensitive Escherichia coli KNabc. A clone vector pUC18 containing nhaC1 or nhaC2 could make KNabc tolerate 0.6 M/0.7 M NaCl or 30 mM/40 mM LiCl and a pH of up to 8.5/9.5, respectively. Functional analysis shows that the Na⁺(K⁺, Li⁺)/H⁺ antiport activities of NhaC1 and NhaC2 are both pH-dependent in the range of pH 7.0-10.0, and the optimal pH is 9.5. Phylogenetic analysis shows that both NhaC1 and NhaC2 belong to the Na⁺/H⁺ antiporter NhaC family of proteins and are significantly distant from the identified NhaC proteins from Bacillus. In summary, we have identified two Na⁺(K⁺, Li⁺)/H⁺ antiporters from N. daqingense.

Natrinema caseinilyticum sp. nov., Natrinema gelatinilyticum sp. nov., Natrinema marinum sp. nov., Natrinema zhouii sp. nov., extremely halophilic archaea isolated from marine environments and a salt mine

Four extremely halophilic archaeal strains (ZJ2^T, BND6^T, DT87^T, and YPL30^T) were isolated from marine environments and a salt mine in China. The 16S rRNA and rpoB' gene sequence similarities among strains ZJ2^T, BND6^T, DT87^T, YPL30^T and the current species of Natrinema were 93.2-99.3% and 89.2-95.8%, respectively. Both phylogenetic and phylogenomic analyses revealed that strains ZJ2^T, BND6^T, DT87^T, and YPL30^T cluster with the Natrinema members. The overall genome-related indexes (ANI, isDDH, and AAI) among these four strains and the current species of genus Natrinema were 70-88%, 22-43% and 75-89%, respectively, clearly below the threshold values for species boundary. Strains ZJ2^T, BND6^T, DT87^T, and YPL30^T could be distinguished from the related species according to differential phenotypic characteristics. The major polar lipids of the four strains were phosphatidic acid (PA), phosphatidylglycerol (PG), phosphatidylglycerol phosphate methyl ester (PGP-Me), sulfated mannosyl glucosyl diether (S-DGD-1), and disulfated mannosyl glucosyl diether (S₂-DGD). The phenotypic, chemotaxonomic, phylogenetic and phylogenomic features indicated that strains ZJ2^T (= CGMCC 1.18786 ^T = JCM 34918 ^T), BND6^T (= CGMCC 1.18777 ^T = JCM 34909 ^T), DT87^T (= CGMCC 1.18921 ^T = JCM 35420 ^T), and YPL30^T (= CGMCC 1.15337 ^T = JCM 31113 ^T) represent four novel species of the genus Natrinema, for which the names, Natrinema caseinilyticum sp. nov., Natrinema gelatinilyticum sp. nov., Natrinema marinum sp. nov., and Natrinema zhouii sp. nov., are proposed.

Natrinema halophilum sp. nov., Natrinema salinisoli sp. nov., Natrinema amylolyticum sp. nov. and Haloterrigena alkaliphila sp. nov., four extremely halophilic archaea isolated from salt mine, saline soil and salt lake

Four halophilic archaeal strains, YPL8T, SLN56T, LT61T and KZCA68T, were isolated from a salt mine, saline soil and a salt lake located in different regions of China. Sequence similarities of 16S rRNA and rpoB′ genes among strains YPL8T, SLN56T, LT61T and the current members of Natrinema were 94.1–98.2 % and 89.3–95.1 %, respectively, while these values among strain KZCA68T and the current members of Haloterrigena were 97.2–97.4 % and 91.7–91.9 %, respectively. The average nucleotide identity, in silico DNA–DNA hybridization and average amino acid identity values among these four strains and their closely related species were all lower than the threshold values for species boundary. All four strains were unable to hydrolyse casein, gelatin, or Tween 80. Strain YPL8T contained phosphatidic acid (PA), phosphatidylglycerol (PG), phosphatidylglycerol phosphate methyl ester (PGP-Me), sulfated mannosyl glucosyl diether (S-DGD-1), disulfated mannosyl glucosyl diether (S2-DGD) and sulfated mannosyl glucosyl diether-phosphatidic acid (S-DGD-PA). Strain SLN56T contained PA, PG, phosphatidylglycerol sulphate (PGS), PGP-Me, S-DGD-1, S2-DGD and S-DGD-PA. Strain LT61T contained PA, PG, PGS, PGP-Me, S-DGD-1 and S2-DGD. The phospholipids of strain KZCA68T were PA, PG and PGP-Me. These results showed that strains YPL8T (=CGMCC 1.13883T=JCM 31181T), SLN56T (=CGMCC 1.14945T=JCM 30832T) and LT61T (=CGMCC 1.14942T=JCM 30668T) represent novel species of the genus Natrinema , for which the names, Natrinema halophilum sp. nov., Natrinema salinisoli sp. nov. and Natrinema amylolyticum sp. nov. are proposed. Strain KZCA68T (=CGMCC 1.17211T=JCM 34158T) represents a novel species of Haloterrigena , for which the name Haloterrigena alkaliphila sp. nov. is proposed.

Phylogenomics of Haloarchaea: The Controversy of the Genera Natrinema-Haloterrigena

The haloarchaeal genera Natrinema and Haloterrigena were described almost simultaneously by two different research groups and some strains studied separately were described as different species of these genera. Furthermore, the description of additional species were assigned to either Natrinema or Haloterrigena, mainly on the basis of the phylogenetic comparative analysis of single genes (16S rRNA gene and more recently rpoB’ gene), but these species were not adequately separated or assigned to the corresponding genus. Some studies suggested that the species of these two genera should be unified into a single genus, while other studies indicated that the genera should remain but some of the species should be reassigned. In this study, we have sequenced or collected the genomes of the type strains of species of Natrinema and Haloterrigena and we have carried out a comparative genomic analysis in order to clarify the controversy related to these two genera. The phylogenomic analysis based on the comparison of 525 translated single-copy orthologous genes and the Overall Genome Relatedness Indexes (i.e., AAI, POCP, ANI, and dDDH) clearly indicate that the species Haloterrigena hispanica, Haloterrigena limicola, Haloterrigena longa, Haloterrigena mahii, Haloterrigena saccharevitans, Haloterrigena thermotolerans, and Halopiger salifodinae should be transferred to the genus Natrinema, as Natrinema hispanicum, Natrinema limicola, Natrinema longum, Natrinema mahii, Natrinema saccharevitans, Natrinema thermotolerans, and Natrinema salifodinae, respectively. On the contrary, the species Haloterrigena turkmenica, Haloterrigena salifodinae, and Haloterrigena salina will remain as the only representative species of the genus Haloterrigena. Besides, the species Haloterrigena daqingensis should be reclassified as a member of the genus Natronorubrum, as Natronorubrum daqingense. At the species level, Haloterrigena jeotgali and Natrinema ejinorense should be considered as a later heterotypic synonyms of the species Haloterrigena (Natrinema) thermotolerans and Haloterrigena (Natrinema) longa, respectively. Synteny analysis and phenotypic features also supported those proposals.

Distribution of Denitrification among Haloarchaea: A Comprehensive Study

Microorganisms from the Halobacteria class, also known as haloarchaea, inhabit a wide range of ecosystems of which the main characteristic is the presence of high salt concentration. These environments together with their microbial communities are not well characterized, but some of the common features that they share are high sun radiation and low availability of oxygen. To overcome these stressful conditions, and more particularly to deal with oxygen limitation, some microorganisms drive alternative respiratory pathways such as denitrification. In this paper, denitrification in haloarchaea has been studied from a phylogenetic point of view. It has been demonstrated that the presence of denitrification enzymes is a quite common characteristic in Halobacteria class, being nitrite reductase and nitric oxide reductase the enzymes with higher co-occurrence, maybe due to their possible role not only in denitrification, but also in detoxification. Moreover, copper-nitrite reductase (NirK) is the only class of respiratory nitrite reductase detected in these microorganisms up to date. The distribution of this alternative respiratory pathway and their enzymes among the families of haloarchaea has also been discussed and related with the environment in which they constitute the major populations. Complete denitrification phenotype is more common in some families like Haloarculaceae and Haloferacaceae, whilst less common in families such as Natrialbaceae and Halorubraceae.

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.

Halostella salina gen. nov., sp. nov., an extremely halophilic archaeon isolated from solar salt

A novel halophilic archaeon designated strain CBA1114^T was isolated from solar salt in the Republic of Korea. Strain CBA1114^T, cells of which were coccoid and Gram-stain-negative, grew in the presence of 15-30 % (w/v) NaCl (optimum, 20 %) and at 20-50 °C (optimum, 40 °C) and pH 7.0-9.0 (optimum, pH 8.0). Strain CBA1114^T required Mg²⁺ for growth. Strain CBA1114^T had three 16S rRNA genes, rrnA, rrnB and rrnC; levels of similarity between the sequences were 99.7-99.9 %. The 16S rRNA gene sequence of strain CBA1114^T showed 91.7 % similarity to that of Haloterrigena thermotolerans PR5^T. In multilocus sequence analysis (MLSA), five housekeeping genes, atpB, EF-2, radA, rpoB' and secY, were found to be closely related to those of the members of the genera Halorientalis(89.7 % similarity of the atpB gene sequence), Halomicroarcula(91.9 %, EF-2), Haloterrigena(85.4 %, radA), Natronoarchaeum(89.2 %, rpoB') and Natrinema(75.7 %, secY). A phylogenetic tree generated from the results of MLSA of the five housekeeping genes showed that strain CBA1114^T was closely related to species of the genus Halorientalis in the family Halobacteriaceae. The major polar lipids were identified as phosphatidylglycerol, phosphatidylglycerol phosphate methyl ester and unidentified lipids. The G+C content of the genomic DNA of strain CBA1114^T was 68.1 mol%. According to the results of phylogenetic, phenotypic and chemotaxonomic analyses, we designate strain CBA1114^T (=JCM 30111^T=KCTC 4206^T) as the type strain of Halostella salina gen. nov., sp. nov., a novel species of a new genus within the family Halobacteriaceae.

Genome sequence of the haloarchaeon Haloterrigena jeotgali type strain A29(T) isolated from salt-fermented food

Haloterrigena jeotgali is a halophilic archaeon within the family Natrialbaceae that was isolated from shrimp jeotgal, a traditional Korean salt-fermented food. A29^T is the type strain of H. jeotgali, and is a Gram-negative staining, non-motile, rod-shaped archaeon that grows in 10 %–30 % (w/v) NaCl. We present the annotated H. jeotgali A29^T genome sequence along with a summary of its features. The 4,131,621 bp genome with a GC content of 64.9 % comprises 4,215 protein-coding genes and 127 RNA genes. The sequence can provide useful information on genetic mechanisms that enable haloarchaea to endure a hypersaline environment.

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)).

Quorum-sensing inhibitory compounds from extremophilic microorganisms isolated from a hypersaline cyanobacterial mat

In this study, extremely halophilic and moderately thermophilic microorganisms from a hypersaline microbial mat were screened for their ability to produce antibacterial, antidiatom, antialgal, and quorum-sensing (QS) inhibitory compounds. Five bacterial strains belonging to the genera Marinobacter and Halomonas and one archaeal strain belonging to the genus Haloterrigena were isolated from a microbial mat. The strains were able to grow at a maximum salinity of 22-25 % and a maximum temperature of 45-60 °C. Hexanes, dichloromethane, and butanol extracts from the strains inhibited the growth of at least one out of nine human pathogens. Only butanol extracts of supernatants of Halomonas sp. SK-1 inhibited growth of the microalga Dunaliella salina. Most extracts from isolates inhibited QS of the acyl homoserine lactone producer and reporter Chromobacterium violaceum CV017. Purification of QS inhibitory dichloromethane extracts of Marinobacter sp. SK-3 resulted in isolation of four related diketopiperazines (DKPs): cyclo(L-Pro-L-Phe), cyclo(L-Pro-L-Leu), cyclo(L-Pro-L-isoLeu), and cyclo(L-Pro-D-Phe). QS inhibitory properties of these DKPs were tested using C. violaceum CV017 and Escherichia coli-based QS reporters (pSB401 and pSB1075) deficient in AHL production. Cyclo(L-Pro-L-Phe) and cyclo(L-Pro-L-isoLeu) inhibited QS-dependent production of violacein by C. violaceum CV017. Cyclo(L-Pro-L-Phe), cyclo(L-Pro-L-Leu), and cyclo(L-Pro-L-isoLeu) reduced QS-dependent luminescence of the reporter E. coli pSB401 induced by 3-oxo-C6-HSL. Our study demonstrated the ability of halophilic and moderately thermophilic strains from a hypersaline microbial mat to produce biotechnologically relevant compounds that could be used as antifouling agents.

Natronoarchaeum mannanilyticum gen. nov., sp. nov., an aerobic, extremely halophilic archaeon isolated from commercial salt

Strain YSM-123T was isolated from commercial salt made from Japanese seawater in Niigata prefecture. Optimal NaCl and Mg2+ concentrations for growth were 4.0–4.5 M and 5 mM, respectively. The isolate was a mesophilic and slightly alkaliphilic haloarchaeon, whose optimal growth temperature and pH were 37 °C and pH 8.0–9.0. Phylogenetic analysis based on 16S rRNA gene sequence analysis suggested that strain YSM-123T is a member of the phylogenetic group defined by the family Halobacteriaceae, but there were low similarities to type strains of other genera of this family (≤90 %); for example, Halococcus (similarity <89 %), Halostagnicola (<89 %), Natronolimnobius (<89 %), Halobiforma (<90 %), Haloterrigena (<90 %), Halovivax (<90 %), Natrialba (<90 %), Natronobacterium (<90 %) and Natronococcus (<90 %). The G+C content of the DNA was 63 mol%. Polar lipid analysis revealed the presence of phosphatidylglycerol, phosphatidylglycerophosphate methyl ester, disulfated diglycosyl diether and an unknown glycolipid. On the basis of the data presented, we propose that strain YSM-123T should be placed in a new genus and species, Natronoarchaeum mannanilyticum gen. nov., sp. nov. The type strain of Natronoarchaeum mannanilyticum is strain YSM-123T (=JCM 16328T =CECT 7565T).

Haloterrigena daqingensis sp. nov., an extremely haloalkaliphilic archaeon isolated from a saline–alkaline soil

A haloalkaliphilic archaeon, strain JX313T, was isolated from a saline–alkaline soil from Daqing, Heilongjiang Province, China. Its morphological, physiological and biochemical features and 16S rRNA gene sequence were determined. Colonies of the strain were orange–red and cells were non-motile cocci and Gram-stain-variable. The strain required at least 1.7 M NaCl for growth, with optimal growth occurring in 2.0–2.5 M NaCl. Growth was observed at 20–50 °C and pH 8.0–10.5, with optimal growth at 35 °C and pH 10.0. The G+C content of its genomic DNA was 59.3 mol%. Phylogenetic analysis of 16S rRNA gene sequences showed that strain JX313T is associated with the genera Haloterrigena and Natrinema and is most closely related to Haloterrigena salina XH-65T (96.2 % sequence similarity) and Haloterrigena hispanica FP1T (96.2 %). DNA–DNA hybridization experiments revealed that the relatedness of strain JX313T to type strains of related species of the genus Haloterrigena or Natrinema was less than 50 %. Furthermore, the cellular polar lipids of strain JX313T, identified as phosphatidylglycerol, phosphatidylglycerol phosphate methyl ester and mannose-2,6-disulfate (1→2)-glucose glycerol diether (S2-DGD), were consistent with the polar lipid characteristics of the genus Haloterrigena. Therefore, phylogenetic analysis, phenotypic assessment and chemotaxonomic data showed that JX313T represents a novel species within the genus Haloterrigena, for which the name Haloterrigena daqingensis sp. nov. is proposed. The type strain is JX313T (=CGMCC 1.8909T =NBRC 105739T).

Haloterrigena salina sp. nov., an extremely halophilic archaeon isolated from a salt lake

A novel extremely halophilic strain, designated XH-65(T), isolated from the salt lake Xilinhot in Inner Mongolia, PR China, was subjected to a polyphasic taxonomic characterization. Strain XH-65(T) is neutrophilic, non-motile and requires at least 2.5 M NaCl for growth, with an optimum at 3.4 M NaCl, and grows at pH 6.0-9.0, with optimum growth at pH 7.5. Strain XH-65(T) grows at 25-50 degrees C, with optimal growth at 37 degrees C. Magnesium is not required for growth. On the basis of 16S rRNA gene sequence analysis, strain XH-65(T) was shown to belong to the genus Haloterrigena and was related to Haloterrigena turkmenica VKM B-1734(T) (98.1 % sequence similarity), Haloterrigena saccharevitans AB14(T) (96.9 %), Haloterrigena thermotolerans PR5(T) (96.3 %), Haloterrigena limicola AX-7(T) (95.8 %) and Haloterrigena hispanica FP1(T) (95.7 %). DNA-DNA hybridization revealed 37 % relatedness between strain XH-65(T) and Htg. turkmenica VKM B-1734(T). The polar lipid composition revealed the presence of phosphatidylglycerol, phosphatidylglycerol phosphate methyl ester and mannose-2,6-disulfate (1-->2)-glucose glycerol diether (S(2)-DGD). The results of the DNA-DNA hybridization and physiological and biochemical tests allowed genotypic and phenotypic differentiation of strain XH-65(T) from the six Haloterrigena species with validly published names. Therefore, strain XH-65(T) represents a novel species, for which the name Haloterrigena salina sp. nov. is proposed, with the type strain XH-65(T) (=CGMCC 1.6203(T) =JCM 13891(T)).

Haloterrigena hispanica sp. nov., an extremely halophilic archaeon from Fuente de Piedra, southern Spain

An extremely halophilic archaeon belonging to the order Halobacteriales was isolated from Fuente de Piedra salt lake, Spain. This strain, designated FP1T, was a pleomorphic coccoid, neutrophilic and required at least 15 % (w/v) NaCl for growth. Strain FP1T grew at 37–60 °C, with optimal growth at 50 °C. Mg2+ was not required, but growth was observed with up to 10 % (w/v) MgSO4. Polar lipid analysis revealed the presence of mannose-6-sulfate(1-2)-glucose glycerol diether as a major glycolipid. Both C20C20 and C20C25 core lipids were present. The genomic DNA G+C content was 62.0 mol%. Phylogenetic analysis based on comparison of 16S rRNA gene sequences demonstrated that the isolate was most closely related to species of the genus Haloterrigena. DNA–DNA reassociation values between strain FP1T and the most closely related species of the genus Haloterrigena (Haloterrigena thermotolerans, Haloterrigena saccharevitans and Haloterrigena limicola) were lower than 29 %. It is therefore considered that strain FP1T represents a novel species of the genus Haloterrigena, for which the name Haloterrigena hispanica sp. nov. is proposed. The type strain is FP1T (=DSM 18328T=ATCC BAA-1310T).

Haloferax larsenii sp. nov., an extremely halophilic archaeon from a solar saltern

Three strains of Gram-negative, aerobic, neutrophilic, extremely halophilic archaea, designated ZJ206T, ZJ203 and ZJ204, were isolated from a solar saltern in Zhe-Jiang Province, China. Phenotypically and on the basis of 16S rRNA gene sequences, the strains were very similar. Comparative 16S rRNA gene analysis revealed 96.4–97.4 % sequence similarity to members of the genus Haloferax. The major polar lipids were C20C20 derivatives of phosphatidylglycerol, phosphatidylglycerol phosphate methyl ester, diglycosyl glycerol diether and sulfated diglycosyl diether. The DNA G+C content of strain ZJ206T was 62.2 mol%. The results of DNA–DNA hybridizations and physiological and biochemical tests allowed genotypic and phenotypic differentiation of the isolates from closely related species. Therefore the isolates should be classified as members of a novel species, for which the name Haloferax larsenii sp. nov. is proposed. The type strain is ZJ206T (=CGMCC 1.5347T=JCM 13917T).

Haloterrigena longa sp. nov. and Haloterrigena limicola sp. nov., extremely halophilic archaea isolated from a salt lake

Halophilic archaeal strains ABH32T and AX-7T were isolated from Aibi salt lake in Xin-Jiang, China, and were subjected to taxonomic studies. The cells of both strains were rod-shaped, and growth required at least 10 % (w/v) NaCl. The cellular polar lipids were identified as phosphatidylglycerol, phosphatidylglycerol phosphate methyl ester and mannose-2,6-disulfate (1→2)-glucose glycerol diether (S2-DGD). The isolates were different in that strain ABH32T did not require magnesium and had strong ability to assimilate sugars for growth, whereas strain AX-7T required magnesium and did not assimilate glucose, sucrose or maltose for growth. Both strain ABH32T and strain AX-7T were most closely related to members of the genera Haloterrigena and Natrinema. On the basis of phenotypic and genotypic characteristics, especially their cellular polar lipids, the two isolates were assigned to the genus Haloterrigena. Moreover, the DNA relatedness values for strains ABH32T and AX-7T with respect to members of the genus Haloterrigena were found to be well below 70 %. Thus, strains ABH32T and AX-7T represent two novel species within the genus Haloterrigena, for which the names Haloterrigena longa sp. nov. (type strain ABH32T=CGMCC 1.5334T=JCM 13562T) and Haloterrigena limicola sp. nov. (type strain AX-7T=CGMCC 1.5333T=JCM 13563T) are proposed.

Halostagnicola larsenii gen. nov., sp. nov., an extremely halophilic archaeon from a saline lake in Inner Mongolia, China

Strain XH-48T was isolated from the sediment of Lake Xilinhot, a saline lake in Inner Mongolia (China). The organism is pleomorphic, neutrophilic and requires at least 2.5 M (15 %) NaCl, but not MgCl2, for growth; it exhibits optimal growth at 3.4 M (20 %) NaCl. The G+C content of its DNA is 61 mol%. 16S rRNA gene sequence analysis revealed that strain XH-48T is a member of the family Halobacteriaceae, but there were low levels of similarity with other members of this family. The highest sequence similarity values (94.5 and 93.3 %) were obtained with the 16S rRNA genes of Natrialba aegyptiaca and Natrialba asiatica, respectively. Polar lipid analyses revealed that strain XH-48T contains phosphatidylglycerol and phosphatidylglyceromethylphosphate, derived from both C20C20 and C20C25 glycerol diethers, and two unidentified glycolipids. On the basis of the data obtained, the novel isolate cannot be classified within any recognized genus. Strain XH-48T should be placed within a novel genus and species within the family Halobacteriaceae, order Halobacteriales, for which the name Halostagnicola larsenii gen. nov., sp. nov. is proposed. The type strain of Halostagnicola larsenii is strain XH-48T (=DSM 17691T=CGMCC 1.5338T=JCM 13463T=CECT 7116T).

Natronorubrum aibiense sp. nov., an extremely halophilic archaeon isolated from Aibi salt lake in Xin-Jiang, China, and emended description of the genus Natronorubrum

An extremely halophilic archaeon (strain 7-3T) was isolated from Aibi salt lake in Xin-Jiang, China. It formed small (<1.0 mm), red, elevated colonies on salt-milk agar medium. Strain 7-3T was able to grow at pH 6.5–9.5 (optimum pH 8.0) and at 20–50 °C (optimum 45 °C). Analysis of its 16S rRNA gene sequence indicated that strain 7-3T was phylogenetically related to members of the genus Natronorubrum, with sequence similarities of 97.0 % to Natronorubrum bangense A33T and 95.2 % to Natronorubrum tibetense GA33T. The G+C content of its DNA was 61.2 mol% (T m). Levels of DNA–DNA relatedness to Nrr. bangense and Nrr. tibetense were 45 and 37 %, respectively. It is concluded that strain 7-3T (=CGMCC 1.4299T=JCM 13488T) should be classified as the type strain of a novel species of the genus Natronorubrum, for which the name Natronorubrum aibiense sp. nov. is proposed. Based on the properties of Nrr. aibiense given here and of those of Nrr. bangense and Nrr. tibetense described previously, an emended description of the genus Natronorubrum is presented.