Salarchaeum japonicum gen. nov., sp. nov., an aerobic, extremely halophilic member of the Archaea isolated from commercial salt

Genome-based classification of the class Halobacteria and description of Haladaptataceae fam. nov. and Halorubellaceae fam. nov

Currently, there are four mainstream taxonomic opinions on the classification of the class Halobacteria at the family and order levels. The International Committee on Systematics of Prokaryotes Subcommittee on the Taxonomy of Halobacteria (ICSP), List of Prokaryotic names with Standing in Nomenclature (LPSN) and National Centre for Biotechnology Information (NCBI) adopted taxonomies have three to four orders and up to eight families, while the Genome Taxonomy Database (GTDB) taxonomy proposes only one order with nine families. To resolve the taxonomic inconsistency, phylogenomic analyses based on concatenated single-copy orthologous proteins and 122 concatenated conserved single-copy marker proteins were conducted to infer the taxonomic status of the current representatives of the class Halobacteria at the family and order levels. The current 76 genera with validly published names of the class Halobacteria were able to be assigned into eight families in one order. On the basis of these results, it is proposed that the current species with validly published names of the class Halobacteria should be remerged into the order Halobacteriales, then assigned to eight families, Haladaptataceae, Haloarculaceae, Halobacteriaceae, Halococcaceae, Haloferacaceae, Natronoarchaeaceae, Natrialbaceae and Halorubellaceae. Thus, Haladaptataceae fam. nov. is described based on Haladaptatus, Halomicrococcus and Halorussus and Halorubellaceae fam. nov. is proposed incorporating Haloarchaeobius and Halorubellus, respectively.

Exploring the Distinct Distribution of Archaeal Communities in Sites Contaminated with Explosives

Most of the research on bioremediation and estimation of microbial diversity in waste contaminated sites is focused on the domain Bacteria, whereas details on the relevance of Archaea are still lacking. The present study examined the archaeal diversity and predicted metabolic pathways in two discrete sites (SITE1 and SITE2) contaminated with explosives (RDX and HMX) by amplicon-targeted sequencing of 16S rRNA genes. In total, 14 soil samples were processed, and 35,758 OTUs were observed, among which 981 OTUs were classified as Archaea, representing ~2.7% of the total microbial diversity in our samples. The majority of OTUs belonged to phyla Euryarchaeota (~49%), Crenarchaeota (~24%), and Thaumarchaeota (~23%), while the remaining (~4%) OTUs were affiliated to Candidatus Parvarchaeota, Candidatus Aenigmarchaeota, and Candidatus Diapherotrites. The comparative studies between explosives contaminated and agricultural soil samples (with no history of explosives contamination) displayed significant differences between the compositions of the archaeal communities. Further, the metabolic pathways pertaining to xenobiotic degradation were presumably more abundant in the contaminated sites. Our data provide a first comprehensive report of archaeal communities in explosives contaminated sites and their putative degradation role in such ecosystems which have been as yet unexplored.

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 alkalitolerans sp. nov., alkali-tolerant haloarchaeon isolated from commercial salt

A Gram-stain-negative, rod-pleomorphic, aerobic, halophilic archaeon, strain MK62-1T, was isolated from commercial salt made from seawater in the Philippines. Strain MK62-1T was able to grow at 2.1-4.7 M NaCl (with optimum at 2.1-2.6 M NaCl), pH 6.5-9.5 (optimum, pH 7.0-7.5) and 20-55 °C (optimum, 45-50 °C). Based on the orthologous 16S rRNA gene sequence, the closest relative was Haloparvum sedimenti JCM 30891T with 99.2 % similarity. The RNA polymerase subunit B' gene sequence also showed the highest similarity (97.4 %) to that of Haloparvum sedimenti DYS4T. The DNA G+C content of MK62-1T was 70.1 mol%, while that of Haloparvum sedimenti JCM 30891T was 69.5 mol% by the HPLC method. The levels of DNA-DNA relatedness between MK62-1T and Haloparvum sedimenti JCM 30891T were 60.6 and 60.8 % (reciprocally). The major polar lipids of the isolate were C20C20 archaeol derivatives of phosphatidylglycerol, phosphatidylglycerol phosphate methyl ester and phosphatidylglycerol sulfate. Based on the phenotypic and phylogenetic analyses, it is proposed that the isolate represents species within the genus Haloparvum, for which the name Haloparvum alkalitolerans sp. nov. is proposed. The type strain is MK62-1T (=JCM 30442T =KCTC 4214T).

A phylogenomic reappraisal of family-level divisions within the class Halobacteria: proposal to divide the order Halobacteriales into the families Halobacteriaceae, Haloarculaceae fam. nov., and Halococcaceae fam. nov., and the order Haloferacales into the families, Haloferacaceae and Halorubraceae fam nov

The evolutionary interrelationships between the archaeal organisms which comprise the class Halobacteria have proven difficult to elucidate using traditional phylogenetic tools. The class currently contains three orders. However, little is known about the family level relationships within these orders. In this work, we have completed a comprehensive comparative analysis of 129 sequenced genomes from members of the class Halobacteria in order to identify shared molecular characteristics, in the forms of conserved signature insertions/deletions (CSIs) and conserved signature proteins (CSPs), which can provide reliable evidence, independent of phylogenetic trees, that the species from the groups in which they are found are specifically related to each other due to common ancestry. Here we present 20 CSIs and 31 CSPs which are unique characteristics of infra-order level groups of genera within the class Halobacteria. We also present 40 CSIs and 234 CSPs which are characteristic of Haloarcula, Halococcus, Haloferax, or Halorubrum. Importantly, the CSIs and CSPs identified here provide evidence that the order Haloferacales contains two main groups, one consisting of Haloferax and related genera supported by four CSIs and five CSPs and the other consisting of Halorubrum and related genera supported by four CSPs. We have also identified molecular characteristics that suggest that the polyphyletic order Halobacteriales contains at least two large monophyletic clusters of organisms in addition to the polyphyletic members of the order, one cluster consisting of Haloarcula and related genera supported by ten CSIs and nineteen CSPs and the other group consisting of the members of the genus Halococcus supported by nine CSIs and 23 CSPs. We have also produced a highly robust phylogenetic tree based on the concatenated sequences of 766 proteins which provide additional support for the relationships identified by the CSIs and CSPs. On the basis of the phylogenetic analyses and the identified conserved molecular characteristics presented here, we propose a division of the order Haloferacales into two families, an emended family Haloferacaceae and Halorubraceae fam. nov. and a division of the order Halobacteriales into three families, an emended family Halobacteriaceae, Haloarculaceae fam. nov., and Halococcaceae fam. nov.

Halorubrum gandharaense sp. nov., an alkaliphilic haloarchaeon from commercial rock salt

A Gram-stain-negative, non-motile, pleomorphic rod-shaped, orange–red-pigmented, facultatively aerobic and haloalkaliphilic archaeon, strain MK13-1T, was isolated from commercial rock salt imported from Pakistan. The NaCl, pH and temperature ranges for growth of strain MK13-1T were 3.0–5.2 M NaCl, pH 8.0–11.0 and 15–50 °C, respectively. Optimal growth occurred at 3.2–3.4 M NaCl, pH 9.0–9.5 and 45 °C. Addition of Mg2+ was not required for growth. The major polar lipids of the isolate were C20C20 and C20C25 archaeol derivatives of phosphatidylglycerol and phosphatidylglycerol phosphate methyl ester. Glycolipids were not detected. The DNA G+C content was 64.1 mol%. The 16S rRNA gene sequence of strain MK13-1T was most closely related to those of the species of the genus Halorubrum, Halorubrum luteum CECT 7303T (95.9 % similarity), Halorubrum alkaliphilum JCM 12358T (95.3 %), Halorubrum kocurii JCM 14978T (95.3 %) and Halorubrum lipolyticum JCM 13559T (95.3 %). The rpoB′ gene sequence of strain MK13-1T had < 90 % sequence similarity to those of other members of the genus Halorubrum. Based on the phylogenetic analysis and phenotypic characterization, strain MK13-1T may represent a novel species of the genus Halorubrum, for which the name Halorubrum gandharaense sp. nov. is proposed, with the type strain MK13-1T ( = JCM 17823T = CECT 7963T).

High resolution depth distribution of Bacteria, Archaea, methanotrophs, and methanogens in the bulk and rhizosphere soils of a flooded rice paddy

The communities and abundances of methanotrophs and methanogens, along with the oxygen, methane, and total organic carbon (TOC) concentrations, were investigated along a depth gradient in a flooded rice paddy. Broad patterns in vertical profiles of oxygen, methane, TOC, and microbial abundances were similar in the bulk and rhizosphere soils, though methane and TOC concentrations and 16S rRNA gene copies were clearly higher in the rhizosphere soil than in the bulk soil. Oxygen concentrations decreased sharply to below detection limits at 8 mm depth. Pyrosequencing of 16S rRNA genes showed that bacterial and archaeal communities varied according to the oxic, oxic-anoxic, and anoxic zones, indicating that oxygen is a determining factor for the distribution of bacterial and archaeal communities. Aerobic methanotrophs were maximally observed near the oxic-anoxic interface, while methane, TOC, and methanogens were highest in the rhizosphere soil at 30–200 mm depth, suggesting that methane is produced mainly from organic carbon derived from rice plants and is metabolized aerobically. The relative abundances of type I methanotrophs such as Methylococcus, Methylomonas, and Methylocaldum decreased more drastically than those of type II methanotrophs (such as Methylocystis and Methylosinus) with increasing depth. Methanosaeta and Methanoregula were predominant methanogens at all depths, and the relative abundances of Methanosaeta, Methanoregula, and Methanosphaerula, and GOM_Arc_I increased with increasing depth. Based on contrasts between absolute abundances of methanogens and methanotrophs at depths sampled across rhizosphere and bulk soils (especially millimeter-scale slices at the surface), we have identified populations of methanogens (Methanosaeta, Methanoregula, Methanocella, Methanobacterium, and Methanosphaerula), and methanotrophs (Methylosarcina, Methylococcus, Methylosinus, and unclassified Methylocystaceae) that are likely physiologically active in situ.

Halocalculus aciditolerans gen. nov., sp. nov., an acid-tolerant haloarchaeon isolated from commercial salt

Three halophilic archaeal strains, MH2-243-1T, MH2-93-1 and MH2-91-1 were isolated from commercial salt samples from Japan, Australia, and Bolivia. Strain MH2-243-1T was able to grow in the presence of 12–30 % (w/v) NaCl (optimum, 18 % NaCl), at pH 4.5–7.0 (optimum, pH 6.0) and at 20–60 °C (optimum, 40 °C). Strains MH2-91-1 and MH2-93-1 grew in slightly different ranges. The orthologous 16S rRNA gene sequences of the three strains were almost identical (99.8–99.9 % similarities), and the closest relative was Salarchaeum japonicum JCM 16327T with 94.2–94.3 % 16S rRNA gene sequence similarities, followed by strains of members of the closely related genera Halobacterium and Halarchaeum . The RNA polymerase subunit B′ gene (rpoB′) sequence also showed the highest similarity (86.6 %) to that of Salarchaeum japonicum JCM 16327T. The DNA G+C contents of strains MH2-243-1T, MH2-93-1 and MH2-91-1 were 68.5, 68.8 and 68.3 mol%, respectively. DNA–DNA relatedness values amongst the three strains were 97–99 %. The polar lipids of the three strains were phosphatidylglycerol, phosphatidylglycerol phosphate methyl ester, and at least seven unidentified glycolipids. The polar lipid composition differed from those of Salarchaeum japonicum and species of the genera Halobacterium and Halarchaeum . Based on the phenotypic and phylogenetic analyses, it is proposed that the isolates represent a novel species of a new genus, for which the name Halocalculus aciditolerans gen. nov., sp. nov. is proposed. The type strain of the type species is MH2-243-1T ( = JCM 19596T = KCTC 4149T) isolated from solar salt produced in Japan. MH2-93-1 ( = JCM 19595) and MH2-91-1 ( = JCM 19594) are additional strains of the type species.

Natribaculum breve gen. nov., sp. nov. and Natribaculum longum sp. nov., halophilic archaea isolated from saline soil

Two halophilic archaeal strains, TRM20010T and TRM20345T, were isolated from saline soil of the Lop Nur region in Xinjiang, north-west China. Cells from the two strains were pleomorphic rods, stained Gram-negative and produced red-pigmented colonies. Strains TRM20010T and TRM20345T were able to grow at 30–62 °C (optimum 37 °C), 0.9–5.1 M NaCl (optimum 2.6 and 3.4 M, respectively) and pH 6.0–10.0 (optimum pH 7.0−7.5) and neither strain required Mg2+ for growth. The major polar lipids of the two strains were phosphatidylglycerol (PG), phosphatidylglycerol phosphate methyl ester (PGP-Me), two glycolipids chromatographically identical to galactosyl mannosyl glucosyl diether (TGD-1) and disulfated mannosyl glucosyl diether (S2-DGD). Phylogenetic analysis based on 16S rRNA and rpoB′ genes revealed that strains TRM20010T and TRM20345T clustered together and formed a distinct clade separated from the related genera Halovivax , Haloterrigena , Halostagnicola , Natronolimnobius and Natrinema . The DNA G+C contents of strains TRM20010T and TRM20345T were 63.9 and 63.8 mol%, respectively. The DNA–DNA hybridization value between strain TRM20010T and strain TRM20345T was 42.8 %. The phenotypic, chemotaxonomic and phylogenetic properties suggested that strains TRM20010T and TRM20345T represent two novel species in a new genus within the family Halobacteriaceae , for which the names Natribaculum breve gen. nov., sp. nov. (type strain TRM20010T = CCTCC AB2013112T = NRRL B-59996T) and Natribaculum longum sp. nov. (type strain TRM20345T = CCTCC AB2013113T = NRRL B-59997T) are proposed.

Phylogenomic analyses and molecular signatures for the class Halobacteria and its two major clades: a proposal for division of the class Halobacteria into an emended order Halobacteriales and two new orders, Haloferacales ord. nov. and Natrialbales ord. nov., containing the novel families Haloferacaceae fam. nov. and Natrialbaceae fam. nov

The Halobacteria constitute one of the largest groups within the Archaea. The hierarchical relationship among members of this large class, which comprises a single order and a single family, has proven difficult to determine based upon 16S rRNA gene trees and morphological and physiological characteristics. This work reports detailed phylogenetic and comparative genomic studies on >100 halobacterial (haloarchaeal) genomes containing representatives from 30 genera to investigate their evolutionary relationships. In phylogenetic trees reconstructed on the basis of 32 conserved proteins, using both neighbour-joining and maximum-likelihood methods, two major clades (clades A and B) encompassing nearly two-thirds of the sequenced haloarchaeal species were strongly supported. Clades grouping the same species/genera were also supported by the 16S rRNA gene trees and trees for several individual highly conserved proteins (RpoC, EF-Tu, UvrD, GyrA, EF-2/EF-G). In parallel, our comparative analyses of protein sequences from haloarchaeal genomes have identified numerous discrete molecular markers in the form of conserved signature indels (CSI) in protein sequences and conserved signature proteins (CSPs) that are found uniquely in specific groups of haloarchaea. Thirteen CSIs in proteins involved in diverse functions and 68 CSPs that are uniquely present in all or most genome-sequenced haloarchaea provide novel molecular means for distinguishing members of the class Halobacteria from all other prokaryotes. The members of clade A are distinguished from all other haloarchaea by the unique shared presence of two CSIs in the ribose operon protein and small GTP-binding protein and eight CSPs that are found specifically in members of this clade. Likewise, four CSIs in different proteins and five other CSPs are present uniquely in members of clade B and distinguish them from all other haloarchaea. Based upon their specific clustering in phylogenetic trees for different gene/protein sequences and the unique shared presence of large numbers of molecular signatures, members of clades A and B are indicated to be distinct from all other haloarchaea because of their uniquely shared evolutionary histories. Based upon these results, it is proposed that clades A and B be recognized as two new orders, Natrialbales ord. nov. and Haloferacales ord. nov., within the class Halobacteria, containing the novel families Natrialbaceae fam. nov. and Haloferacaceae fam. nov. Other members of the class Halobacteria that are not members of these two orders will remain part of the emended order Halobacteriales in an emended family Halobacteriaceae.

Halapricum salinum gen. nov., sp. nov., an extremely halophilic archaeon isolated from non-purified solar salt

A halophilic archaeal strain, designated CBA1105(T), was isolated from non-purified solar salt. Strain CBA1105(T) was found to have three 16S rRNA genes, rrnA, rrnB and rrnC; similarities between the 16S rRNA gene sequences were 99.5-99.7 %. The phylogenetic analysis of the 16S rRNA gene sequences showed that strain CBA1105(T) forms a distinct clade with the strains of the closely related genera, Halorientalis and Halorhabdus, with similarities of 94.2 % and 93.9-94.2 %, respectively. Multilocus sequence analysis confirmed that strain CBA1105(T) is closely related to the genus Halorhabdus or Halorientalis. Growth of the strain was observed in 15-30 % NaCl (w/v; optimum 20 %), at 30-45 °C (optimum 37 °C) and pH 7.0-8.0 (optimum pH 7.0) and with 0-0.5 M MgCl2·6H2O (optimum 0.05-0.2 M). The cells of the strain were observed to be Gram-stain negative and pleomorphic with coccoid or ovoid-shape. The cells lysed in distilled water. Tweens 20, 40 and 80 were found to be hydrolysed but starch, casein and gelatine were not. The cells were unable to reduce nitrate under aerobic conditions. Assays for indole formation and urease activity were negative and no growth was observed under anaerobic conditions. Cells were found to be able to utilize L-glutamate, D-glucose, L-maltose, D-mannose and sucrose as sole carbon sources. The polar lipids were identified as phosphatidylglycerol, phosphatidylglycerol phosphate methyl ester, unidentified glycolipids and an unidentified phospholipid. The G+C content of strain CBA1105(T) was determined to be 66.0 mol%. The phenotypic, chemotaxonomic and phylogenetic properties suggest that the strain represents a novel species of a novel genus within the family Halobacteriaceae, for which the name Halapricum salinum is proposed with CBA1105(T) (= KCTC 4202(T) = JCM 19729(T)) as the type strain.

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

A halophilic archaeal strain, GX48(T), was isolated from the Gangxi marine solar saltern near Weihai city in Shandong Province, China. Cells of the strain were rod-shaped, stained Gram-negative and formed red-pigmented colonies. Strain GX48(T) was able to grow at 25-50 °C (optimum 37 °C), in the presence of 1.4-4.8 M NaCl (optimum 2.6 M NaCl), with 0-1.0 M MgCl2 (optimum 0.05 M MgCl2) and at pH 5.5-9.5 (optimum pH 7.0). Cells lysed in distilled water and the minimal NaCl concentration to prevent cell lysis was 8 % (w/v). The major polar lipids of the strain were phosphatidylglycerol, phosphatidylglycerol phosphate methyl ester and two major glycolipids chromatographically identical to those of Natronoarchaeum mannanilyticum YSM-123(T) and Natronoarchaeum philippinense 294-194-5(T). 16S rRNA gene analysis revealed that strain GX48(T) had two dissimilar 16S rRNA genes and both of them were phylogenetically related to those of the two current members of the genus Natronoarchaeum (96.2-98.3 % similarities). The rpoB' gene sequence similarities between strain GX48(T) and Natronoarchaeum mannanilyticum YSM-123(T) and Natronoarchaeum philippinense 294-194-5(T) were 96.0 % and 94.7 %, respectively. The DNA G+C content of strain GX48(T) was 66.2 mol%. Strain GX48(T) showed low DNA-DNA relatedness with the two members of the genus Natronoarchaeum. It was concluded that strain GX48(T) ( = CGMCC 1.10388(T) = JCM 17119(T)) represents a novel species of the genus Natronoarchaeum, for which the name Natronoarchaeum rubrum sp. nov. is proposed. An emended description of the genus Natronoarchaeum is also presented.

Salinisphaera japonica sp. nov., a moderately halophilic bacterium isolated from the surface of a deep-sea fish, Malacocottus gibber, and emended description of the genus Salinisphaera

A moderately halophilic, slightly acidophilic, aerobic bacterium, designated strain YTM-1(T), was isolated from the body surface of Malacocottus gibber. Cells were Gram-stain-negative, short rods or cocci, approximately 0.9-1.1 µm long and 1.0-1.8 µm wide. Strain YTM-1(T) was able to grow with 1-30% NaCl (optimum, 7.5-10%, w/v), at 4-30 °C (optimum, 20-25 °C) and at pH 3.8-9.5 (optimum, pH 5.0-5.5). Phylogenetic analysis based on 16S rRNA gene sequence similarities showed that strain YTM-1(T) belonged to the genus Salinisphaera with low similarity values to the type strains of recognized species of this genus (<94.8-94.4%). The polar lipids of strain YTM-1(T) consisted of diphosphatidylglycerol, phosphatidylcholine, phosphatidylglycerol, phosphatidylethanolamine, phosphatidylserine, three unknown phospholipids and one unknown lipid. The predominant isoprenoid quinone was Q-8. The major fatty acids were C19:0ω8c cyclo, C18:1ω7c, C16:1ω5c and C16:0. The DNA G+C content of strain YTM-1(T) was 67.3 mol%. These phylogenetic, physiological and chemotaxonomic data indicated that strain YTM-1(T) represents a novel species of the genus Salinisphaera, for which the name Salinisphaera japonica sp. nov. is proposed. The type strain is YTM-1(T) (=JCM 18087(T)=CECT 8012(T)). An emended description of the genus Salinisphaera is also proposed.

Halobellus limi sp. nov. and Halobellus salinus sp. nov., isolated from two marine solar salterns

Two halophilic archaea, strains TBN53(T) and CSW2.24.4(T), were characterized to elucidate their taxonomic status. Strain TBN53(T) was isolated from the Taibei marine solar saltern near Lianyungang city, Jiangsu province, China, whereas strain CSW2.24.4(T) was isolated from a saltern crystallizer in Victoria, Australia. Cells of the two strains were pleomorphic, stained Gram-negative and produced red-pigmented colonies. Strain TBN53(T) was able to grow at 25-55 °C (optimum 45 °C), with 1.4-5.1 M NaCl (optimum 2.6-3.9 M NaCl), with 0-1.0 M MgCl(2) (optimum 0-0.1 M MgCl(2)) and at pH 5.5-9.5 (optimum pH 7.0), whereas strain CSW2.24.4(T) was able to grow at 25-45 °C (optimum 37 °C), with 2.6-5.1 M NaCl (optimum 3.4 M NaCl), with 0.01-0.7 M MgCl(2) (optimum 0.05 M MgCl(2)) and at pH 5.5-9.5 (optimum pH 7.0-7.5). Cells of the two isolates lysed in distilled water. The minimum NaCl concentrations that prevented cell lysis were 8 % (w/v) for strain TBN53(T) and 12 % (w/v) for strain CSW2.24.4(T). The major polar lipids of the two strains were phosphatidylglycerol, phosphatidylglycerol phosphate methyl ester and phosphatidylglycerol sulfate, with two glycolipids chromatographically identical to sulfated mannosyl glucosyl diether and mannosyl glucosyl diether, respectively. Trace amounts of other unidentified lipids were also detected. On the basis of 16S rRNA gene sequence analysis, strains TBN53(T) and CSW2.24.4(T) showed 94.1 % similarity to each other and were closely related to Halobellus clavatus TNN18(T) (95.0 and 94.7 % similarity, respectively). Levels of rpoB' gene sequence similarity between strains TBN53(T) and CSW2.24.4(T), and between these strains and Halobellus clavatus TNN18(T) were 88.5, 88.5 and 88.1 %, respectively. The DNA G+C contents of strains TBN53(T) and CSW2.24.4(T) were 69.2 and 67.0 mol%, respectively. The level of DNA-DNA relatedness between strain TBN53(T) and strain CSW2.24.4(T) was 25 %, and these two strains showed low levels of DNA-DNA relatedness with Halobellus clavatus TNN18(T) (30 and 29 % relatedness, respectively). Based on these phenotypic, chemotaxonomic and phylogenetic properties, two novel species of the genus Halobellus are proposed to accommodate these two strains, Halobellus limi sp. nov. (type strain TBN53(T) = CGMCC 1.10331(T) = JCM 16811(T)) and Halobellus salinus sp. nov. (type strain CSW2.24.4(T) = DSM 18730(T) = CGMCC 1.10710(T) = JCM 14359(T)).

Salinarchaeum laminariae gen. nov., sp. nov.: a new member of the family Halobacteriaceae isolated from salted brown alga Laminaria

Halophilic archaeal strains R26(T) and R22 were isolated from the brown alga Laminaria produced at Dalian, Liaoning Province, China. Cells from the two strains were pleomorphic rods and Gram negative, and colonies were red pigmented. Strains R26(T) and R22 were able to grow at 20-50°C (optimum 37°C) in 1.4-5.1 M NaCl (optimum 3.1-4.3 M) at pH 5.5-9.5 (optimum pH 8.0-8.5) and neither strain required Mg(2+) for growth. Cells lyse in distilled water and the minimum NaCl concentration required to prevent cell lysis was 8% (w/v) for strain R26(T) and 12% (w/v) for strain R22. The major polar lipids of the two strains were phosphatidylglycerol, phosphatidylglycerol phosphate methyl ester and minor phosphatidylglycerol sulfate; glycolipids were not detected. Phylogenetic analyses based on 16S rRNA genes and rpoB' genes revealed that strains R26(T) and R22 formed a distinct clade with the closest relative, Natronoarchaeum mannanilyticum. The DNA G+C content of strains R26(T) and R22 was 65.8 and 66.4 mol%, respectively. The DNA-DNA hybridization value between strains R26(T) and R22 was 89%. The phenotypic, chemotaxonomic and phylogenetic properties suggest that the strains R26(T) and R22 represent a novel species in a new genus within the family Halobacteriaceae, for which the name Salinarchaeum laminariae gen. nov., sp. nov. is proposed. The type strain is R26(T) (type strain R26(T) = CGMCC 1.10590(T) = JCM 17267(T), reference strain R22 = CGMCC 1.10589).