- Volume 72, Issue 10, 2022

A novel bacterial strain, N4T, was isolated from the soil of a groundnut Arachis hypogaea field in Nghean province, Vietnam. The phylogenetic, chemotaxonomic and phenotypic characteristics of this strain were determined. Cells of strain N4T were Gram-negative, aerobic, endospore-forming and rod-shaped. Strain N4T grew at 20–37 °C (optimum, 30 °C), pH 6–10 (optimum, pH 7) and 0–5 % NaCl (optimum, 0 %). Phylogenetic analysis based on 16S rRNA gene sequences showed that strain N4T belonged to the genus Paenibacillus and was closely related to Paenibacillus harenae B519T (=KCTC 3951T) and Paenibacillus alkaliterrae KSL-134T (=KCTC 3956T) with 96.3 and 96.5% gene sequence similarity, respectively. It contained meso-diaminopimelic acid as the diagnostic diamino acid in the cell-wall peptidoglycan. The DNA G+C content was 52.9 mol%. The major isoprenoid quinone was MK-7. Anteiso-C15 : 0 and iso-C16 : 0 were the dominant cellular fatty acids. Based on phylogenetic, physiological and biochemical characteristics, strain N4T represents a novel species of the genus Paenibacillus , for which the name Paenibacillus vietnamensis sp. nov. is proposed. The type strain is N4T (=KCTC 33932T= VTCC 12236T).

Clostridium aurantibutyricum , Clostridium felsineum and Clostridium roseum share a very high similarity based on multi-locus sequence analysis. In this study, their correct taxonomic status was determined using genomic and phenotypic investigations. Average nucleotide identity based on MUMmer alignment of the genomes and in silico DNA–DNA hybridization resulted in values of 98.55–100 and 78.7–100 %, respectively, strongly indicating that all strains are members of the same species. In addition, morphological investigations, fatty acid analyses and substrate utilization tests revealed no striking differences between the strains. Therefore, we propose the reclassification of C. aurantibutyricum and C. roseum as later heterotypic synonyms of C. felsineum . The type strain is lodged in several culture collections (ATCC 17788T=DSM 794T=NCIMB 10690T).

Six Gram-stain-positive, aerobic and irregular-rod-shaped actinobacteria (ZJ1313T, ZJ1307, MC1495T, Y192, 603T and X2025) were isolated from the Qinghai–Tibet Plateau of China and were characterized using a polyphasic taxonomic method. Phylogenetic analysis based on 16S rRNA gene sequences indicated that the six new strains formed three distinct clusters within the genus Nocardioides , and strains ZJ1313T and ZJ1307 were most closely related to N. solisilvae JCM 31492T (16S rRNA gene sequence similarity, 98.0 %), MC1495T and Y192 to N. houyundeii 78T (98.5 %), and 603T and X2025 to N. dokdonensis JCM 14815T (97.6 %). The digital DNA–DNA hybridization values of strains ZJ1313T, MC1495T and 603T among each other and with type strains of their closest relatives were all below the 70 % cut-off point, but values within each pair of new strains were all higher than the threshold. The major fatty acids of these strains were iso-C16 : 0, C17 : 1  ω8c or C18 : 1  ω9c. MK-8(H4) was the predominant respiratory menaquinone and ʟʟ−2,6-diaminopimelic acid was the diagnostic diamino acid. All the strains shared diphosphatidylglycerol (predominant), phosphatidylglycerol, phosphatidylcholine and phosphatidylinositol as the common polar lipids, with minor difference in the types of unidentified phospholipids, glycolipids and lipids. The G+C contents based on genomic DNA of strains ZJ1313T, MC1495T and 603T were 72.5, 72.1 and 73.2 mol%, respectively. The above results suggested that strain pairs ZJ1313T/ZJ1307, MC1495T/Y192 and 603T/X2025 represent three new species of genus Nocardioides , for which the names Nocardioides ochotonae sp. nov. (ZJ1313T=GDMCC 4.177T=KCTC 49537T=JCM 34185T), Nocardioides campestrisoli sp. nov. (MC1495T=GDMCC 4.176T=KCTC 49536T=JCM 34307T) and Nocardioides pantholopis sp. nov. (603T=CGMCC 4.7510T=DSM 106494T) are proposed accordingly.

Two novel actinobacterial strains, designated MMS20-R2-23T and MMS20-R2-29T, were isolated from riverside soil and subjected to taxonomic characterization. Both strains were Gram-stain-positive, aerobic, non-motile and filamentous, and formed orange to strong orange-brown coloured colonies, which later turned black. Both strains grew optimally at mesophilic temperatures, neutral to slightly alkaline pH and in the absence of NaCl. Analysis of 16S rRNA gene sequences indicated that the two novel strains fell into phylogenetic clusters belonging to the genus Micromonospora . Strains MMS20-R2-23T and MMS20-R2-29T showed the highest 16S rRNA gene sequence similarity to Micromonospora phytophila SG15T (99.3 %) and Micromonospora humida MMS20-R1-14T (99.4 %), respectively. Based on the comparative genome analysis, strain MMS20-R2-23T had the highest orthologous average nucleotide identity (orthoANI) value of 92.70 % with Micromonospora matsumotoense DSM 44100T, and MMS20-R2-29T shared 94.99 % with Micromonospora wenchangensis CCTCC AA 2012002T. Besides, the digital DNA–DNA hybridization (dDDH) values of MMS20-R2-23T and MMS20-R2-29T with the same species were 47.6 and 59.2% respectively, which were also highest among the compared species, thus confirming the separation of each strain at species level from related species. The orthoANI and dDDH values between MMS20-R2-23T and MMS20-R2-29T were 92.18 and 44.9% respectively. The genomes of strains MMS20-R2-23T and MMS20-R2-29T were estimated as 7.56 Mbp and 7.13 Mbp in size, and the DNA G+C contents were 72.5 and 72.9 mol%, respectively. The chemotaxonomic properties of both strains were consistent with those of the genus. The novel strains showed antimicrobial activity against a broad range of microbes, in particular Gram-positive bacteria and yeasts. It is evident that each of the isolated strains merits recognition as representing novel species of Micromonospora , for which the names Micromonospora antibiotica sp. nov. (type strain=MMS20-R2-23T=KCTC 49542T=JCM 34495T) and Micromonospora humidisoli sp. nov. (type strain=MMS20-R2-29T=KCTC 49543T=JCM 34496T) are proposed.

Six Gram-stain-positive, aerobic or facultative anaerobic, catalase-positive, urease- and oxidase-negative, rod-shaped bacteria (zg-ZUI157T/zg-ZUI40, zg-ZUI222T/zg-ZUI199 and zg-ZUI188T/ zg-ZUI168) were characterized by a polyphasic approach. Optimal growth of the six strains was observed at pH 7.0 and 28 °C. Phylogenetic analyses based on the 16S rRNA gene and 247 core genes revealed that they belong to genus Cellulomonas . The three type strains have low digital DNA-DNA hybridization (19.3–30.1%) and average nucleotide identity values (78.0-85.5%) with all available genomes in the genus Cellulomonas , and a DNA G+C content range of 73.0-74.6 mol%. The major fatty acids detected in strain pairs zg-ZUI157T/zg-ZUI40 and zg-ZUI 222T/zg-ZUI199 were C16:0, anteiso-C15:0 and anteiso A-C15:1, and C16:0, anteiso-C15:0, anteiso A-C15:1 and anteiso-C17:0 in strain pair zg-ZUI188T/zg-ZUI168. Diphosphatidylglycerol, phosphatidylglycerol and phosphatidylinositol mannosides were the major polar lipids detected in the three novel species. MK-9(H4) was the predominant quinone detected in strains zg-ZUI222T (87.4 %) and zg-ZUI188T (91.4 %), and MK-9(H4) (49.1 %) and MK-8 (43.4 %) in strain zg-ZUI157T. The cell-wall sugars detected in the three novel species mainly contained rhamnose. The cell-wall peptidoglycan type of the three novel species was A4β, with an inferred l-Orn–d-Asp interpeptide bridge for strains zg-ZUI157T and zg-ZUI222T, and l-Orn–d-Glu for strain zg-ZUI188T. Based on the results of the phenotypic, phylogenetic, genomic hybridization, average nucleotide identity and chemotaxonomic analyses, the six strains should be classified as belonging to three novel Cellulomonas species, for which the names Cellulomonas dongxiuzhuiae sp. nov. (zg-ZUI157T=GDMCC 1.2559T=KCTC 49678T), Cellulomonas wangleii sp. nov. (zg-ZUI222T=GDMCC 1.2501T=KCTC 49675T) and Cellulomonas fengjieae sp. nov. (zg-ZUI188T=GDMCC 1.2563T=KCTC 49674T) are proposed.

An aerobic, Gram-stain-positive and non-spore-forming strain, designated C1-1T, was isolated from a fellfield soil sample collected from frost-sorted polygons on Jane Col, Signy Island, Maritime Antarctic. Cells with a size of 0.65–0.9×1.2–1.7 µm have a flagellar motile apparatus and exhibit a rod–coccus growth cycle. Optimal growth conditions were observed at 15–20 °C, pH 7.0 and NaCl concentration up to 0.5 % (w/v) in the medium. The 16S rRNA gene sequence of C1-1T showed the highest pairwise similarity of 98.77 % to Arthrobacter glacialis NBRC 113092T. Phylogenetic trees based on the 16S rRNA and whole-genome sequences revealed that strain C1-1T belongs to the genus Arthrobacter and is most closely related to members of the ‘ Arthrobacter psychrolactophilus group’. The G+C content of genomic DNA was 58.95 mol%. The original and orthologous average nucleotide identities between strain C1-1T and A. glacialis NBRC 113092T were 77.15 % and 77.38 %, respectively. The digital DNA–DNA relatedness values between strain C1-1T and A. glacialis NBRC 113092T was 21.6 %. The polar lipid profile was composed mainly of diphosphatidylglycerol, phosphatidylglycerol, phosphatidylinositol and an unidentified glycolipid. The predominant cellular fatty acids were anteiso-C15 : 0 (75 %) and anteiso-C17 : 0 (15.2 %). Menaquinone MK-9(H2) (86.4 %) was the major respiratory quinone in strain C1-1T. The peptidoglycan type was determined as A3α (l-Lys–l-Ala3; A11.6). Based on all described phylogenetic, physiological and chemotaxonomic characteristics, we propose that strain C1-1T (=DSM 112353T=CCM 9148T) is the type strain of a novel species Arthrobacter polaris sp. nov.

The taxonomic status of two Gordonia strains, designated BEN371 and CON9T, isolated from stable foams on activated sludge plants was the subject of a polyphasic study which also included the type strains of Gordonia species and three authenticated Gordonia amarae strains recovered from such foams. Phylogenetic analyses of 16S rRNA gene sequences showed that these isolates formed a compact cluster suggesting a well-supported lineage together with a second branch containing the G. amarae strains. A phylogenomic tree based on sequences of 92 core genes extracted from whole genome sequences of the isolates, the G. amarae strains and Gordonia type strains confirmed the assignment of the isolates and the G. amarae strains to separate but closely associated lineages. Average nucleotide index (ANI) and digital DNA–DNA hybridisation (dDDH) similarities showed that BEN371 and CON9T belonged to the same species and had chemotaxonomic and morphological features consistent with their assignment to the genus Gordonia . The isolates and the G. amarae strains were distinguished using a range of phenotypic features and by low ANI and dDDH values of 84.2 and 27.0 %, respectively. These data supplemented with associated genome characteristics show that BEN371 and CON9T represent a novel species of the genus Gordonia . The name proposed for members of this taxon is Gordonia pseudamarae sp. nov. with isolate CON9T (=DSM 43602T=JCM 35249T) as the type strain.

The family   Streptomycetaceae   is a large and diverse family within the phylum   Actinomycetota  . The members of the family are known for their ability to produce medically important secondary metabolites, notably antibiotics. In this study, 19 type strains showing low 16S rRNA gene similarity (<97.3 %) to other members of the family   Streptomycetaceae   were identified and their high genetic diversity was reflected in a phylogenomic analysis using conserved universal proteins. This analysis resulted in the identification of six distinct genus-level clades, with two separated from the genus   Streptacidiphilus   and four separated from the genus   Streptomyces  . Compared with members of the genera   Streptacidiphilus   and   Streptomyces  , average amino acid identity (AAI) analysis of the novel genera identified gave values within the range of 63.9–71.3 %, as has been previously observed for comparisons of related but distinct bacterial genera. The whole-genome phylogeny was reconstructed using PhyloPhlAn 3.0 based on an optimized subset of conserved universal proteins, the results of AAI and percentage of conserved proteins (POCP) analyses indicated that these phylogenetically distinct taxa may be assigned to six novel genera, namely Actinacidiphila gen. nov., Mangrovactinospora gen. nov., Peterkaempfera gen. nov., Phaeacidiphilus gen. nov., Streptantibioticus gen. nov. and Wenjunlia gen. nov.

A novel cellulose-degrading actinobacterium, designated strain NEAU-S10T, was isolated from soil collected from Chifeng, Inner Mongolia Autonomous Region, PR China, and characterized using a polyphasic approach. Pairwise similarity of the 16S rRNA gene sequence showed that strain NEAU-S10T was a representative of Saccharothrix and was closely related to Saccharothrix carnea NEAU-yn17T (99.2 %), Saccharothrix saharensis SA152T (99.0 %), Saccharothrix texasensis DSM 44231T (98.5 %) and Saccharothrix xinjiangensis NBRC 101911T (98.5 %). Physiological and chemotaxonomic characteristics of the strain further supported its affiliation to the genus Saccharothrix . The whole-cell sugars contained galactose, ribose and mannose. The polar lipids contained diphosphatidylglycerol, phosphatidylmonomethylethanolamine, phosphatidylethanolamine, phosphatidylinositol and phosphatidylinositol mannoside. The predominant menaquinones were MK-9(H0), MK-9(H2), MK-9(H4) and MK-10(H4). The major fatty acids were iso-C16 : 0, C16 : 0, anteiso-C17 : 0, iso-C15 : 0 and iso-C17 : 0. The genomic DNA G+C content was 71.8 mol%. The levels of digital DNA–DNA hybridization between isolate and S. carnea NEAU-yn17T, S. saharensis SA152T and S. texasensis DSM 44231T were 40.1 % (37.6–42.6 %), 38.soap8 % (36.3–41.3 %) and 44.8 % (42.2–47.3 %) and the ANI values between them were determined to be 90.2, 89.8 and 91.7 %, the results indicated that strain NEAU-S10T could be distinguished from its reference strains. The assembled genome sequence of strain NEAU-S10T was found to be 10 305 394 bp long. The NCBI Prokaryotic Genome Annotation Pipeline (PGAP) revealed 8 994 protein-coding genes. Genomic analysis and Congo red staining test indicated that strain NEAU-S10T had the potential to degrade cellulose. The genomic and phenotypic results indicate that strain NEAU-S10T represents a novel species of the genus Saccharothrix , for which the name Saccharothrix luteola sp. nov. is proposed, with NEAU-S10T (=CCTCC AA 2020037T=JCM 34800T) as the type strain.

A polyphasic taxonomic study was performed on an unidentified previously described Arcanobacterium -like Gram-positive strain 2701T isolated from an anal swab of a dead male harbour seal. Comparative 16S rRNA sequencing showed that the bacterium belonged to the genus Arcanobacterium in the family Arcanobacteriaceae . The genome sequence of the strain was obtained by Borowiak et al. [ 1 ]. The genome had a G+C content of 49 mol% and a total length of 1.94 Mb. The presence of the major menaquinone MK-9(H4) supported the affiliation of the isolate with the genus Arcanobacterium . The polar lipid profile consisted of diphosphatidylglycerol and an unidentified phospholipid as major components and two unidentified lipids, a further unidentified phospholipid, two unidentified phosphoglycolipids as well as phosphatidylglycerol. The major fatty acids were C16 : 0, C18 : 1 and C18 : 0. Biochemical and phylogenetic analyses clearly distinguished the isolate from other members of the genus Arcanobacterium and closely related other species. Based on these results, it is proposed that the unknown Arcanobacterium sp. strain 2701T should be classified as representing a novel species with the name Arcanobacterium buesumense sp. nov. The type strain is 2701T (=DSM 112952T=LMG 32446T).

Four mesophilic actinobacteria (HY002T, HY442, HY366T and HY285) isolated from the faeces of bats collected in southern China were found to be strictly aerobic, non-motile, rod-shaped, oxidase-negative, Gram-stain-positive and catalase-positive. Strains HY002T and HY366T contained meso-diaminopimelic acid as the diagnostic diamino acid and MK-9(H2) the sole respiratory quinone. Arabinose, galactose and ribose were detected in the whole-cell hydrolysates of both type strains. The main cellular fatty acids (> 10.0%) of all strains were C16 : 0, C18 : 1  ω9c, 10-methyl-C18 : 0 and summed feature 3. Strains HY002T and HY366T contained diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol and phosphatidyl inositol mannosides as the major polar lipids. The phylogenetic/phylogenomic analyses based on 16S rRNA gene and genomic sequence comparison revealed that the four strains belong to the genus Gordonia , most closely related to G. neofelifaecis NRRL B-59395T(98.2–98.3% sequence similarity) on the EzBioCloud database. The G+C contents of strains HY002T and HY366T based on genomic DNA were 66.5 and 66.9%, respectively. The DNA–DNA relatedness values between the two types strains and members of the genus Gordonia were far below 70 % (18.6–23.1 %). All genotypic and phenotypic data indicated that the four strains are representatives of two novel separate species, for which the names Gordonia zhenghanii sp. nov. and Gordonia liuliyuniae sp. nov. are proposed, with HY002T (=CGMCC 4 7757T=JCM 34 878T) and HY366T (=CGMCC 1 19146T=JCM 34 879T) as the respective type strains.

A urease-producing Gram-stain-positive actinobacterium, designated strain T5T, was isolated from a soil sample collected at a highway hillslope in Selangor, Malaysia. The strain was found to produce pale yellowish-pink aerial mycelia with smooth long chain spores and extensively branched light yellowish-pink substrate mycelia on oatmeal agar. Strain T5T grew at 15–37 °C, pH 6–11, and tolerated up to 9 % (w/v) NaCl, with optimal growth occurring at 28 °C, pH 6–9 and without NaCl. The whole-cell sugar hydrolysate of strain T5T contained galactose, glucose and ribose. The ll-diaminopimelic acid isomer was detected in the cell wall. Diphosphatidylglycerol, phosphatidylcholine, phosphatidylethanolamine, phosphatidylglycerol and phosphatidylinositol were found to be the predominant polar lipids. The main fatty acids were anteiso-C17 : 0, iso-C16 : 0, anteiso-C15 : 0 and iso-C14 : 0. Comparative analysis of the 16S rRNA gene sequences indicated that strain T5T belonged to Streptomyces of the family Streptomycetaceae with the highest 16S rRNA gene sequence similarity to Streptomyces lichenis LCR6-01T (99.0 %). The overall genome relatedness indices revealed that the closest related species was S. lichenis LCR6-01T with 89.4 % average nucleotide identity and 33.7 % digital DNA–DNA hybridization. Phylogeny analyses showed that strain T5T was closely related to Streptomyces fradiae , Streptomyces lavendofoliae , Streptomyces lichenis , Streptomyces roseolilacinus and Streptomyces somaliensis . Based on these polyphasic data, strain T5T represents a novel species, for which the name Streptomyces solincola sp. nov. is proposed. The type strain is T5T (=TBRC 5137T= DSM 42166T).

Two novel actinobacteria with the ability to degrade kerosene, designated as B3033T and Y57T, were isolated from mangrove sediments in Tieshan Harbour, South China Sea. Both strains are Gram-staining-positive, non-spore forming, slow-growing, oxidase-positive, non-motile and aerobic. Their major cellular fatty acids were C16 : 0 and C18 : 1ω9c. Analysis of 16S rRNA gene sequences revealed the close relationship of strain B3033T to Mycobacterium kyogaense DSM 107316T (99.4 % nucleotide identity) and strain Y57T to Mycolicibacterium chubuense ATCC 27278T (98.7 %) and Mycolicibacterium rufum JS14T (98.7 %). Whole genome average nucleotide blast identity (ANI) and the digital DNA–DNA hybridization (dDDH) values between the two isolates and the type strains of species of the genus Mycolicibacterium were lower than 94 and 45 %, respectively, which were below the threshold values of 95 % (for ANI) and 70 % (for dDDH) recommended for bacterial species differentiation. The genome sequence of B3033T comprised a circular 11.0 Mb chromosome with a DNA G+C content of 68.1 mol%. Y57T had a genome size of 5.6 Mb and a DNA G+C content of 68.7 mol%. Genes involved in degradation of aromatic compounds and copper resistance were identified in the genomes of both strains that could improve their adaptive capacity to the mangrove environment. These results combined with those of chemotaxonomic analyses, MALDI-TOF MS profiles and phenotypic analyses support the affiliation of these strains to two novel species within the genus Mycolicibacterium , for which we propose the names Mycolicibacterium aurantiacum sp. nov. B3033T (=KCTC 49712T=MCCC 1K04526T) and Mycolicibacterium xanthum sp. nov. Y57T (=KCTC 49711T=MCCC 1K04875T) as type strains.

Two strictly anaerobic, Gram-stain-positive, non-motile bacteria (strains OPF53T and TOC12T) were isolated from mouse intestines. Strains OPF53T and TOC12T grew at pH 5.5–9.0 and 5.0–9.0, respectively, and at temperatures of 30–45 °C. The cell morphologies of these strains were short rods and rods, respectively, and the cells possessed intracellular granules. The major cellular fatty acids of OPF53T were C18  :  1 cis 9 and C18  :  1 cis 9 dimethyl acetal, whereas those of TOC12T were C18  :  0 and C18  :  1 cis 9. In OPF53T, the main end-products of modified peptone–yeast extract–glucose (PYG) fermentation were lactate, formate and butyrate, whereas, in addition to these acids, TOC12T also produced hydrogen. The genomes of OPF53T and TOC12T were respectively 2.2 and 2.0 Mbp in size with a DNA G+C contents of 69.1 and 58.7 %. The 16S rRNA gene sequences of OPF53T and TOC12T showed the highest similarity to members of the family Atopobiaceae , namely, Olsenella phocaeensis Marseille-P2936T (94.3 %) and Olsenella umbonata KCTC 15140T (93.2 %), respectively. Phylogenetic analyses revealed that both isolates formed distinct lineages from other genera of the family Atopobiaceae . In addition, the two strains were characterized by relatively low 16S rRNA gene sequence similarity (93.4 %) and can be distinguished by their distinctive traits (including cell shape, DNA G+C content, and major fatty acids profiles). On the basis of their polyphasic taxonomic properties, these isolates represent two noel species of two novel genera within the family Atopobiaceae , for which the names Granulimonas faecalis gen. nov., sp. nov. (OPF53T=JCM 35015T=KCTC 25474T) and Leptogranulimonas caecicola gen. nov., sp. nov. (TOC12T=JCM 35017T=KCTC 25472T) are proposed.

A novel thermoacidophilic archeaon, strain J1T (=DSM 112778T,=JCM 34702T), was isolated from a hot pool in a volcanic area of Java, Indonesia. Cells of the strain were irregular, motile cocci of 1.0–1.2 µm diameter. Aerobic, organoheterotrophic growth with casamino acids was observed at an optimum temperature of 70 °C in a range of 55–78 °C and at an optimum pH of 3 in a range of 1.5 to 5. Various organic compounds were utilized, including a greater variety of sugars than has been reported for growth of other species of the genus. Chemolithoautotrophic growth was observed with reduced sulphur compounds, including mineral sulphides. Ferric iron was reduced during anaerobic growth with elemental sulphur. Cellular lipids were calditoglycerocaldarchaeol and caldarchaeol with some derivates. The organism contained the respiratory quinone caldariellaquinone. On the basis of phylogenetic and chemotaxonomic comparison with its closest relatives, it was concluded that strain J1T represents a novel species, for which the name Metallosphaera javensis is proposed. Low DNA–DNA relatedness values (16S rRNA gene <98.4%, average nucleotide identity (ANI) <80.1%) distinguished J1T from other species of the genus Metallosphaera and the DNA G+C content of 47.3% is the highest among the known species of the genus.

Two extremely halophilic archaeal strains, PSR5T and PSR8T, were isolated from a saline soil sample collected from the Tarim Basin, Xinjiang, PR China. Both strains had two copies of the 16S rRNA genes rrn1 and rrn2, showing 2.6 and 3.9% divergence, respectively. The rrn1 gene of PSR5T showed 98.4 and 95.3% similarity to the rrn1 and rrn2 genes of strain PSR8T; the rrn2 gene of PSR5T displayed 97.4 and 96.7% similarity to those of strain PSR8T, respectively. Phylogenetic analyses based on the 16S rRNA and rpoB′ genes revealed that strains PSR5T and PSR8T formed a single cluster, and then tightly clustered with the current four Haladaptatus species (93.5–97.1% similarities for the 16S rRNA gene and 89.3–90.9% similarities for the rpoB′ gene, respectively). Several phenotypic characteristics differentiate strains PSR5T and PSR8T from current Haladaptatus members. The polar lipids of the two strains are phosphatidic acid, phosphatidylglycerol, phosphatidylglycerol phosphate methyl ester phosphatidylglycerol sulphate and three glycolipids. One of the glycolipids is sulphated mannosyl glucosyl diether, and the remaining two glycolipids are unidentified. The average nucleotide identity, in silico DNA–DNA hybridization, amino acid identity and percentage of conserved proteins values between the two strains were 88.5, 39.1, 89.3 and 72.8 %, respectively, much lower than the threshold values proposed as a species boundary. These values among the two strains and Haladaptatus members were 77.9–79.2, 22.0–23.5, 75.1–78.2 and 56.8–69.9 %, respectively, much lower than the recommended threshold values for species delimitation. These results suggested that strains PSR5T and PSR8T represent two novel species of Haladaptatus . Based on phenotypic, chemotaxonomic, genomic and phylogenetic properties, strains PSR5T (=CGMCC 1.16851T=JCM 34141T) and PSR8T (=CGMCC 1.17025T=JCM 34142T) represent two novel species of the genus Haladaptatus , for which the names Haladaptatus halobius sp. nov. and Haladaptatus salinisoli sp. nov. are proposed.

An anaerobic, hydrogenotrophic methane-producing archaeon was isolated from an alkaline thermal spring (42 °C, pH 9.0) in New Caledonia. This methanogen, designated strain CANT, is alkaliphilic, thermotolerant, with Gram-positive staining non-motile cells. Strain CANT grows autotrophically using hydrogen exclusively as an energy source and carbon dioxide as the sole carbon source (without the requirement of yeast extract or other organic compounds). It grows at 20–45 °C (optimum, 45 °C) and pH 7.3–9.7 (optimum, pH 9.0). NaCl is not required for growth (optimum 0 %) but is tolerated up to 1.5 %. It resists novobiocin, streptomycin and vancomycin but is inhibited by ampicillin and penicillin, among other antibiotics. The genome consists of a circular chromosome (2.2 Mb) containing 2126 predicted protein-encoding genes with a G+C content of 36.4 mol%. Phylogenetic analysis based on the 16S rRNA gene sequence indicated that strain CANT is a member of the genus Methanobacterium , most closely related to the alkaliphilic Methanobacterium alcaliphilum WeN4T with 98.5 % 16S rRNA gene sequence identity. The genomes of strain CANT and M. alcaliphilum DSM 3459, sequenced in this study, share 71.6 % average nucleotide identity and 14.0 % digital DNA–DNA hybridization. Therefore, phylogenetic and physiological results indicate that strain CANT represents a novel species, for which the name Methanobacterium alkalithermotolerans sp. nov. is proposed, and strain CANT (=DSM 102889T= JCM 31304T) is assigned as the type strain.

Three extremely halophilic archaeal strains (LT55T, SQT-29-1T and WLHS5T) were isolated from Gobi saline soil and a salt lake, China. These strains were most related to the genera Natribaculum and Halovarius (92.6–95.1 % similarities), and showed low similarities with other genera within the family Natrialbaceae based on 16S rRNA genes. Phylogenomic analysis confirmed that the three strains formed a distinct clade separated from the related genera Halostagnicola and Natronococcus , which indicated that they may represent a novel genus of the family Natrialbaceae . The average nucleotide identity (ANI), in silico DNA–DNA hybridization (isDDH) and average amino acid identity (AAI) values among the three strains were no more than 87, 34 and 85 %, respectively, much lower than the threshold values for species demarcation. The major phospholipids of the three strains were phosphatidic acid (PA), phosphatidylglycerol (PG) and phosphatidylglycerol phosphate methyl ester (PGP-Me). The glycolipid profiles of the three strains were diverse; sulfated mannosyl glucosyl diether (S-DGD-1) and disulfated mannosyl glucosyl diether (S2-DGD) were found in strains LT55T and WLHS5T, while mannosyl glucosyl diether (DGD-1) and S-DGD-1 in strain SQT-29-1T. The combination of phenotypic, chemotaxonomic, phylogenetic and genomic analyses suggested that strains WLHS5T (=CGMCC 1.13781T = JCM 33558T), SQT-29-1T (=CGMCC 1.16065T = JCM 33554T) and LT55T (=CGMCC 1.15188T = JCM 30838T) represent three novel species of a new genus within the family Natrialbaceae , for which the names, Halosolutus amylolyticus gen. nov., sp. nov., Halosolutus gelatinilyticus sp. nov. and Halosolutus halophilus sp. nov., are proposed. Genome-based classification of genera Natribaculum and Halovarius revealed that Halovarius luteus should be transferred to the genus Natribaculum as Natribaculum luteum comb. nov. and Natribaculum longum as a heterotypic synonym of Natribaculum breve Liu et al. 2015.