Tomato plant growth promotion and drought tolerance conferred by three arbuscular mycorrhizal fungi is mediated by lipid metabolism.

Arbuscular mycorrhizal fungi (AMF) can promote plant growth and enhance plant drought tolerance with varying effect size among different fungal species. However, the linkage between the variation and the lipid metabolism, which is exclusively derived from plants, has been little explored thus far. Here, we established AM symbiosis between tomato (Solanum lycopersicum) plants and three AMF species (Rhizophagus intraradices, Funneliformis mosseae, Rhizophagus irregularis) under well watered (WW) or drought stressed (DS) conditions in pot experiment. The plant biomass, chlorophyll fluorescence Fv/Fm, shoot P content and mycorrhizal colonization were determined. Meanwhile, fatty acid (FA) profiles and relative expression of genes encoding for nutrition exchange (SlPT4, SlPT5, RAM2, STR/STR2) in roots were also monitored. DS significantly decreased plant biomass while AMF significantly increased it, with three fungal species varying in their growth promoting capacity and drought tolerance capacity. The growth promoting effect of R. irregularis was lower than those of R. intraradices and F. mosseae, and was associated with higher mycorrhizal colonization and more consumption of lipids. However, the drought tolerance capacity of R. irregularis was greater than those of R. intraradices and F. mosseae, and was associated with less decrease in mycorrhizal colonization and lipid content. We also found that AMF mediated plant drought tolerance via regulating both AM specific FAs and non-AM specific FAs in a complementary manner. These data suggest that lipid metabolism in AM plays a crucial role in plant drought tolerance mediated by AMF.

Curtobacterium caseinilyticum sp. nov., Curtobacterium subtropicum sp. nov. and Curtobacterium citri sp. nov., isolated from citrus phyllosphere.

Three novel Gram-stain-positive, aerobic and rod-shaped bacterial strains, designated RHCKG28T, RHCJP20T and RHCKG23T, were isolated from phyllosphere of healthy citrus leaves collected from Renhua County in Guangdong Province, PR China. 16S rRNA gene sequences comparison and phylogenetic analyses showed that they all belonged to the genus Curtobacterium, among which strain RHCKG28T showed the highest similarity to Curtobacterium herbarum NBRC 103064T (99.3 %), while strains RHCJP20T and RHCKG23T showed 99.2 and 99.0 % similarity to Curtobacterium citreum JCM 1345T, respectively. Phylogenomic analysis showed that the three novel strains were most closely related to C. citreum JCM 1345T and Curtobacterium albidum JCM 1344T. The novel strains could be distinguished from their closely related type strains in terms of enzyme activities, substrate assimilation and fatty acid profiles. In addition, the average nucleotide identity and digital DNA-DNA hybridization values between the novel strains and closely related type strains were 84.4‒89.5 % and 24.5‒34.1 %, respectively, which were below the threshold values for species delimitation. They all took anteiso-C15 : 0, iso-C16 : 0 and anteiso-C17 : 0 as the major fatty acids, menaquinone 9 (MK-9) as the sole predominant respiratory quinone, and ornithine as the principal cell-wall diamino acid. The major polar lipids consisted of phosphatidylglycerol, diphosphatidylglycerol and several unidentified glycolipids. The phenotypic, genotypic and chemotaxonomic data supported that they represent three distinct novel species of the genus Curtobacterium, for which the names Curtobacterium caseinilyticum sp. nov., Curtobacterium subtropicum sp. nov. and Curtobacterium citri sp. nov. are proposed, with RHCKG28T (=GDMCC 1.2667T=JCM 34828T), RHCJP20T (=GDMCC 1.2668T=JCM 34829T) and RHCKG23T (=GDMCC 1.2669T=JCM 34830T) as the type strains, respectively.

Description of Xanthocytophaga agilis sp. nov. and Xanthocytophaga flavus sp. nov. of the new genus Xanthocytophaga gen. nov and the proposal of Rhodocytophagaceae fam. nov. within the order Cytophagales.

Four Gram-staining-negative, aerobic, yellow-pigmented and rod-shaped bacteria, named strains BD1B2-1T, NT2B1T, YF14B1 and DM2B3-1, were isolated from four rhizosphere soil samples of banana in China. Comparison of the 16S rRNA gene sequences showed that all these strains were most closely related to an invalidly published species, 'Rhodocytophaga rosea' 172606-1, with similarities ranging from 87.7 to 88.0%. According to the phylogenomic analysis, the four strains were clustered in an independent lineage and closely related to the genus Rhodocytophaga. The genomic sizes of these strains were approximately 9.49-9.77 Mbp with the DNA G + C contents of 38.8-39.0 mol%. They all contained C16:1 ω5c, iso-C15:0 and iso-C17:0 3-OH as the major fatty acids and menaquinone 7 as the only respiratory quinone. They all had phosphatidylethanolamine as the major polar lipids. Based on phenotypic and phylogenomic characteristics, the four strains should represent two novel species within a novel genus, for which the names Xanthocytophaga agilis gen. nov., sp. nov. (BD1B2-1T = GDMCC 1.2890T = JCM 35374T) and Xanthocytophaga flavus sp. nov. (NT2B1T = GDMCC 1.2889T = JCM 35375T) are proposed; the former is assigned as the type species of the novel genus Xanthocytophaga gen. nov. In addition, based on the phenotypic and phylogenomic data, we proposed to reclassify the existing genus Rhodocytophaga in the family Cytophagaceae into a novel family Rhodocytophagaceae fam. nov. The novel family consists of the type genus Rhodocytophaga and the novel genus Xanthocytophaga.

Dyella humicola sp. nov., Dyella subtropica sp. nov., Dyella silvatica sp. nov. and Dyella silvae sp. nov., isolated from subtropical forest soil.

Four novel bacterial strains, designated RBB1W86T, RXD159T, RBB189T and RLT163T, were isolated from subtropical forest soil of the Nanling National Nature Reserve located in Guangdong Province, PR China. 16S rRNA gene phylogeny indicated their affiliation to the genus Dyella, among which strains RBB1W86T and RXD159T were closely related to Dyella halodurans CGMCC 1.15435T with 16S rRNA gene sequence similarities of 98.8 and 99.5 %, respectively, and strains RBB189T and RLT163T were closely related to Dyella tabacisoli CGMCC 1.16273T (98.8 %) and Dyella japonica JCM 21530T (99.4 %), respectively. Phylogenomic analysis based on 92 core genes showed consistent phylogeny with the 16S rRNA gene phylogeny for strains RBB1W86T, RBB189T and RLT163T, while strain RXD159T showed a closer relationship with D. tabacisoli CGMCC 1.16273T and strain RBB189T. The genome-derived average nucleotide identity (ANI) values between the newly isolated strains and their closely related species were 70.18‒90.20 %, and the corresponding digital DNA-DNA hybridization (dDDH) values were 20.80‒40.30 %. Meanwhile, the ANI and dDDH values between each pair of the newly isolated strains were 75.80‒79.77 % and 21.30‒23.30 %, respectively. They all took iso-C15 : 0 and summed feature 9 (10-methyl C16  : 0 and/or iso-C17  : 1 ω9c) as the major fatty acids. Moreover, C16 : 0, iso-C16 : 0, iso-C17 : 0 and summed feature 3 (C16 : 1 ω7c and/or C16 : 1 ω6c) were also variously distributed as major components. They all took ubiquinone 8 as the only predominant respiratory quinone and phosphatidylglycerol, diphosphatidylglycerol, phosphatidylethanolamine and an unidentified phospholipid as the major polar lipids. Phosphatidylmethylethanolamine was only present in strain RBB189T as another major component. Based on the results of phenotypic, genotypic and chemotaxonomic analyses, the newly isolated strains could be clearly distinguished from their closely related species and should represent four distinct novel species of the genus Dyella, for which the names Dyella humicola sp. nov. (type strain RBB1W86T=GDMCC 1.1901T=KACC 21988T), Dyella subtropica sp. nov. (type strain RXD159T=GDMCC 1.1902T=KACC 21989T), Dyella silvatica sp. nov. (type strain RBB189T=GDMCC 1.1900T=KACC 21990 T) and Dyella silvae sp. nov. (type strain RLT163T=GDMCC 1.1916T=KACC 21991T) are proposed.

Characterization of phytopathogen-preying Hyalangium versicolor sp. nov., and proposal for the reclassification of Cystobacter gracilis as Hyalangium gracile comb. Nov.

A Gram-staining-negative, aerobic, and rod-shaped with tapered end myxobacterium, designed as strain H56D21T, was isolated from forest soil sampled from the Diaoluo Mountain National Nature Reserve located in Hainan Province, PR China. It showed prey ability on two kinds of phytopathogens including both fungi (Fusarium solani, Fusarium graminearum, and Fusarium oxysporum) and bacteria (Ralstonia solanacearum and Xanthomonas campestris). Phylogenetic analyses based on the 16S rRNA gene and core genes  sequences revealed that strain H56D21T belonged to the genus Hyalangium and was most closely related to Cystobacter gracilis DSM 14753 T and Hyalangium minutum DSM 14724 T. Genome comparison showed 85.6% and 82.3% of average nucleotide identity between strain H56D21T and the above two type strains and 29.8% and 25.1% of digital DNA-DNA hybridization , respectively. The novel strain had a large genome size of 13.56 Mbp and a high  DNA G + C content of 67.1%. Genome annotation identified 46 secondary metabolite biosynthesis gene clusters and 187 CAZymes-encoding genes. The major fatty acids contained iso-C15:0, iso-C15:0 DMA, C16:1 ω5c, and iso-C17:0. The dominant respiratory quinone was menaquinone 8. Based on the phenotypic, chemotaxonomic and phylogenetic analyses, we suggested that strain H56D21T should represent a novel species of the genus Hyalangium with a proposed name of Hyalangium versicolor sp. nov. (type strain H56D21T = GDMCC 1.1944 T = KCTC 82613 T) and Cystobacter gracilis should be reclassified as Hyalangium gracile comb. nov.

Cooperation of arbuscular mycorrhizal fungi and bacteria to facilitate the host plant growth dependent on soil pH.

Almost all plants grow well in their native soils. We hypothesized that soil microbes promote the growth of their hosts in native soils by the example of soil pH. Here, bahiagrass (Paspalum notatum Flugge) indigenous to subtropical soils was grown in the native soil (the original pH = 4.85) or in pH-adjusted soils with sulfur (pH = 3.14 or 3.34) or calcium hydroxide (pH = 6.85, 8.34, 8.52 or 8.59). Plant growth, soil chemical property, and microbial community composition were characterized to reveal the microbial taxa promoting plant growth in the native soil. Results showed that shoot biomass was the highest in the native soil, while both the decrease and increase in the soil pH reduced the biomass. Compared with other soil chemical properties, soil pH was the top edaphic factor contributing to the differentiation in arbuscular mycorrhizal (AM) fungal and bacterial communities. The top 3 most abundant AM fungal OTUs belonged to Glomus, Claroideoglomus, and Gigaspora, while the top 3 most abundant bacterial OTUs belonged to Clostridiales, Sphingomonas, and Acidothermus, respectively. Regression analyses between microbial abundances and shoot biomass revealed that the most abundant Gigaspora sp. and Sphingomonas sp. were the most promotive fungal and bacterial OTUs, respectively. The application of these two isolates to bahiagrass solely or in combination indicated that Gigaspora sp. was more promotive than Sphingomonas sp. across the soil pH gradient, and they positively interacted to enhance biomass only in the native soil. We demonstrate that microbes cooperate to facilitate host plants to grow well in their native soils with the original pH. Meanwhile, a high-throughput sequencing-guided pipeline to efficiently screen for beneficial microbes is established.

Pseudomonas citri sp. nov., a potential novel plant growth promoting bacterium isolated from rhizosphere soil of citrus.

A novel potential plant growth promoting bacterium, designated OPS13-3T, was isolated from rhizosphere soil of citrus in Aotou Town of Guangzhou, Guangdong Province, PR China. It showed high ability to dissolve insoluble inorganic phosphate and organic phosphorus and to produce 3-indoleacetic acid (IAA) and siderophore. Cells of the novel strain were Gram-stain-negative, rod-shaped, aerobic and motile with polar flagellum. It shared the highest 16S rRNA gene similarity with Pseudomonas mucoides CCUG 74874T (98.7%) and P. bijieensis LMG 31948T (98.7%). Phylogenetic analyses based the 16S rRNA gene and genome sequences revealed that strain OPS13-3T belonged to the genus Pseudomonas, and was most closely related to P. mediterranea ICMP 14184T and P. corrugate ICMP 5819T. The average nucleotide identity (ANI) and DNA-DNA hybridization (dDDH) values between the novel strain and closely relatives with high 16S rRNA gene similarities were 80.8‒87.5% and 24.7‒34.6%, respectively, which were much below the threshold values for species delimitation. The major fatty acids included C16:0, C10:0 3-OH and summed feature 3 (C16:1ω7c and/or C16:1ω6c). It took ubiquinone 9 as the predominant respiratory quinone and the polar lipids contained phosphatidylglycerol (PG), diphosphatidylglycerol (DPG), phosphatidylethanolamine (PE), three unidentified phospholipids, an unidentified aminophospholipid and an unidentified lipid. Based on the phylogenetic, phenotypic and chemotaxonomic analyses and genome comparison, strain OPS13-3T should be considered as a novel species of the genus Pseudomonas, for which the name Pseudomonas citri sp. nov. is proposed (type strain OPS13-3T = GDMCC 1.3118T = JCM 35385T).

Genome-based taxonomic classification of the closest-to-Comamonadaceae group supports a new family Sphaerotilaceae fam. nov. and taxonomic revisions.

Many genera closest to the family Comamonadaceae have not been classified into any family; moreover, some of them are not monophyletic groups beyond the genus level. To resolve the taxonomic uncertainty of the closest-to-Comamonadaceae (CTC) group, we performed 16S rRNA gene- and genome-based phylogenetic analyses combined with genome relatedness indices and phenotypic traits comparison. Phylogenies based on the 16S rRNA gene and genome sequences demonstrated that the CTC group formed a coherent and robust monophyletic lineage and was sister to the family Comamonadaceae, thereby proposing the CTC group as a novel family, Sphaerotilaceae fam. nov. The resolved genus- and species-level taxonomic relationships of this new family were then validated by the phylogenomic reconstruction and comparisons of genome relatedness indices including digital DNA-DNA hybridization and average nucleotide identity (ANI) as well as comprehensive phenotypic analysis for type strains. Finally, we reclassified all misidentified genera and species, resulting in 19 new combinations, and proposed Sphaerotilaceae-specific thresholds of ANI and average amino acid identity for genus delineation. Collectively, this study has established a sound taxonomic framework of the novel family Sphaerotilaceae and will help guide future taxonomic efforts and prevent the propagation of taxonomic errors.

Aureoterrolides B‒M: Eremophilane-type sesquiterpenoids isolated from Aspergillus aureoterreus and their cytotoxicity.

Uncovered by genome sequence analyses, twelve undescribed sesquiterpenoids designated aureoterrolides B‒M, were isolated from the culture broth of the fungus Aspergillus aureoterreus together with two known analogues. They are unusual eremophilanes with an oxidized C-4, of which aureoterrolide J is an unreported furanoeremophilane comprising a 3/6/6/5/3 pentacyclic architecture with a rare 3,6-spiro ring system. Their structures and absolute configurations were unambiguously assigned by extensive spectroscopic method and theoretical ECD calculation. All isolated compounds were evaluated their cytotoxicity, and aureoterrolides A, B, and I-K showed moderate cytotoxic activity against three human cancer cell lines (HL-60, HepG-2, and SKOV-3) with IC50 values ranging from 4.53 ± 0.05 to 24.71 ± 0.16 µM. Among them, aureoterrolide A exhibited activity such close to the positive control and apoptotic effect on HL-60 cells at a concentration of 5.0 µM.

Microvirga terricola sp. nov. and Microvirga solisilvae sp. nov, isolated from forest soil.

Two Gram-staining-negative, aerobic and rod-shaped strains, designated c23x22T and sex2T, were isolated from forest soil collected from Chebaling National Nature Reserve in Guangdong Province and Limu Mountain National Forest Park in Hainan Province, P. R. China, respectively. Phylogenetic analyses based on 16S rRNA gene sequences revealed that they belonged to the genus Microvirga, and strain c23 x22T was most closely related to 'Microvirga alba' KCTC 72385, while strain sex2T showed close relationship with Microvirga guangxiensis CGMCC 1.7666T. The average nucleotide identity and digital DNA-DNA hybridization values between strains c23 x22T and sex2T and their close relatives, 'M. alba' KCTC 72385 and M. guangxiensis CGMCC 1.7666T, were all below the threshold values for species delimitation. The predominant quinones of the two novel strains were ubiquinone 10, and the major fatty acids contained C19:0 cyclo ω8c and summed feature 8 (C18:1 ω7c and/or C18:1 ω6c). Their predominant polar lipids were phosphatidylglycerol, diphosphatidylglycerol, phosphatidylethanolamine and phosphatidylcholine. The phenotypic, genotypic and chemotaxonomic analyses clearly supported that strains c23 x 22T and sex2T represent two novel species of the genus Microvirga, for which the name Microvirga terricola sp. nov. (type strain c23 x 22T = GDMCC 1.1700T = KCTC 62432T) and Microvirga solisilvae sp. nov. (type strain sex2T = GDMCC 1.1651T = KACC 21311T) are proposed, respectively.

Corallococcus silvisoli sp. nov., a novel myxobacterium isolated from subtropical forest soil.

An orange-pigmented myxobacterium, designated strain c25j21T, was isolated from subtropical forest soil collected from the Chebaling National Nature Reserve in Guangdong Province, China. Phylogenetic analysis based on the 16S rRNA gene and core genes clearly showed that the novel strain was affiliated within the genus Corallococcus and most closely related to Corallococcus aberystwythensis DSM 108846T (99.3% 16S rRNA gene sequence similarity), while C. exercitus DSM 108849T (99.2%) and C. carmarthensis DSM 108842T (99.0%) were the next most closely related type strains. The draft genome sequence of strain c25j21T was 9.23 Mb in length with a G + C content of 70.7 mol%. The average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values between strain c25j21T and its closely related type strains were 88.1-89.1 and 34.1-36.3%, respectively. The major fatty acids contained iso-C15:0, iso-C17:0, iso-C17:1ω5c and iso-C17:0 2-OH. The predominant respiratory quinone was menaquinone 7. Based on phylogenetic, phenotypic and chemotaxonomic analysis, strain c25j21T represents a novel species of the genus Corallococcus, for which the name Corallococcus silvisoli sp. nov. is proposed. The type strain is c25j21T (= GDMCC 1.1387T = KCTC 62437T).

Chitinophaga rhizophila sp. nov., isolated from rhizosphere soil of banana.

A Gram-stain-negative, aerobic and rod-shaped bacterium, designated as strain B61T, was isolated from rhizosphere soil of banana collected from Dongguan, Guangdong Province, PR China. Growth occurred at 15-40 °C, within a pH range of pH 6.0-9.0. Results of 16S rRNA gene sequence similarity and phylogenetic analyses showed that strain B61T was most closely related to 'Chitinophaga agri' KACC 21303 (98.9 %) and Chitinophaga pinensis DSM 2588T (98.8 %). The genome size was 7.6 Mb with a G+C content of 45.2 mol%. The genome-inferred average nucleotide identity values between strain B61T and two closely related strains were 79.2 and 79.3 %, respectively, with corresponding digital DNA-DNA hybridization values of 22.3 and 22.6 %. The major fatty acids of the novel strain were iso-C15:0, C16:1 ω5c and iso-C17:0 3-OH and the sole respiratory quinone was menaquinone 7 (MK-7). The polar lipids consisted of phosphatidylethanolamine, five unidentified aminolipids, four unidentified glycolipids and six unidentified lipids. The phenotypic and phylogenetic results clearly supported that strain B61T represents a novel species of the genus Chitinophaga, for which the name Chitinophaga rhizophila, sp. nov. is proposed, with the type strain B61T (=GDMCC 1.2608T=KCTC 82856T).

Collimonas silvisoli sp. nov. and Collimonas humicola sp. nov., two novel species isolated from forest soil.

Three aerobic, Gram-stain-negative, non-motile and rod-shaped bacteria, designated strains RXD178T, RXD172-2 and RLT1W51T, were isolated from two forest soil samples of Nanling National Nature Reserve in Guangdong Province, PR China. Phylogenetic analyses based on 16S rRNA gene sequences and 92 core genes showed that they belonged to the genus Collimonas, and were most closely related to four validly published species with similarities ranging from 99.4 to 98.2 %. The genomic DNA G+C contents of strains RXD178T, RXD172-2 and RLT1W51T were 57.1, 59.5 and 59.4 mol%, respectively. The genome-derived average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values between the novel strains and closely related type species were below 37.90 and 89.34 %, respectively. Meanwhile, the ANI and dDDH values between strains RXD172-2 and RLT1W51T were 98.27 and 83.50 %, respectively. The three novel strains contained C16 : 0, C17 : 0 cyclo and summed feature 3 (C16 : 1 ω6c and/or C16 : 1 ω7c) as the major fatty acids, and summed feature 8 (C18 : 1 ω6c and/or C18 : 1 ω7c) comprised a relative higher proportion in strain RXD178T than in other strains. Both strains RXD172-2 and RLT1W51T had phosphatidylglycerol (PG), phosphatidylethanolamine (PE), diphosphatidylglycerol (DPG) and an unidentified aminophospholipid (APL) as the main polar lipids while only PE and APL were detected in strain RXD178T. Ubiquinone 8 was the predominant quinone. Based on the phenotypic, chemotaxonomic, phylogenetic and genomic analyses, strain RXD178T should be considered as representing one novel species within the genus Collimonas and strains RXD172-2 and RLT1W51T as another one, for which the names Collimonas silvisoli sp. nov. and Collimonas humicola sp. nov. are proposed, with RXD178T (=GDMCC 1.1925T=KACC 21987T) and RLT1W51T (=GDMCC 1.1923T=KACC 21985T) as the type strains, respectively.

Culture-dependent and -independent methods revealed an abundant myxobacterial community shaped by other bacteria and pH in Dinghushan acidic soils.

Myxobacteria are one of the most promising secondary metabolites producers. However, they are difficult to isolate and cultivate. To obtain more myxobacteria and know the effects of environmental factors on myxobacterial community, we characterized myxobacterial communities in Dinghushan acidic forest soils of pH 3.6-4.5 with culture-dependent and -independent techniques, and analyzed environmental factors shaping myxobacterial communities. A total of 21 myxobacteria were isolated using standard cultivation methods, including eleven isolates of Corallococcus, nine isolates of Myxococcus and one isolate of Archangium, and contained three potential novel species. In addition, a total of 67 unknown myxobacterial operational taxonomic units (OTUs) were obtained using high-throughput sequencing method. The abundance of Myxococcales account for 0.9-2.2% of bacterial communities, and Sorangium is the most abundant genus (60.1%) in Myxococcales. Correlation analysis demonstrated that bacterial diversity and soil pH are the key factors shaping myxobacterial community. These results revealed an abundant myxobacterial community which is shaped by other bacteria and pH in Dinghushan acidic forest soils.

Hymenobacter fodinae sp. nov. and Hymenobacter metallicola sp. nov., isolated from abandoned lead-zinc mine.

Two novel strains, designated 92R-1T and 9PBR-1T, were isolated from abandoned lead-zinc ore collected in Meizhou, Guangdong Province, PR China. Phylogenetic analyses based on 16S rRNA gene sequences showed that they fell into the genus of Hymenobacter and formed two distinct lineages. Strain 92R-1T was most closely related to Hymenobacter wooponensis JCM 19491T (98.7 %) and Hymenobacter gelipurpurascens LMG 21873T (98.5 %), while strain 9PBR-1T was most closely related to Hymenobacter chitinivorans LMG 21951T (99.0 %), Hymenobacter elongatus JCM 17223T (98.7 %) and Hymenobacter aquaticus JCM 31653T (98.1 %). Strain 92R-1Tshared average nucleotide identity values of 80.0-83.7 % and digital DNA-DNA hybridization values of 23.1-27.1 % with its closely related type strains, respectively, while strain 9PBR-1T shared corresponding values of 80.3-83.2 % and 23.6-26.7 % with its closely related type strains, respectively. The two novel strains could be clearly distinguished from their closely related type strains by enzyme activities and substrates assimilation, respectively. Both of them took iso-C15:0, summed feature 3 (C16:1 ω7c and/or C16:1 ω6c), summed feature 4 (iso-C17:1 I and/or anteiso-C17:1 B) and C16:1 ω5c as major fatty acids, and showed clear differences from their closely relatives in the contents of several components. They contained menaquinone 7 as the major respiratory quinone and phosphatidylethanolamine as the dominant polar lipid. The G+C contents of strains 92R-1T and 9PBR-1T were 56.7 and 59.5 mol%, respectively. The results clearly supported that strains 92R-1T and 9PBR-1T represent two distinct novel species within the genus Hymenobacter, for which the names Hymenobacter fodinae sp. nov. (type strain 92R-1T=GDMCC 1.1493T=JCM 32697T) and Hymenobacter metallicola sp. nov. (type strain 9PBR-1T=GDMCC 1.1491T=JCM 32698T) are proposed.

Chitinophaga tropicalis sp. nov., isolated from forest soil.

A novel bacterial strain, designated ysch24T, was isolated from a forest soil sample collected from the Cat Tien National Park, southern Vietnam. Cells were Gram-stain-negative, aerobic, gliding, filamentous or rod-shaped. The results of 16S rRNA gene analyses revealed that strain ysch24T belongs to the genus Chitinophaga, and was most closely related to Chitinophaga silvisoli GDMCC 1.1411T (97.4 %), followed by Chitinophaga oryziterrae JCM 16595T (97.3 %) and Chitinophaga sancti NBRC 15057T (96.9 %). The average nucleotide identity and digital DNA-DNA hybridization values between strain ysch24T and closely related type strains were 72.0-74.0 % and 19.1-19.4 %, respectively. Major fatty acids were iso-C15 : 0, C16 : 1 ω5c and iso-C17 : 0 3-OH and the predominant respiratory quinone was menaquinone 7. Polar lipids consisted of phosphatidylethanolamine, four unidentified aminophospholipids, two unidentified phospholipids and four unidentified lipids. The genomic DNA G+C content was 45.6 mol%. The study clearly showed that strain ysch24T should represent a novel species of the genus Chitinophaga, for which the name Chitinophaga tropicalis sp. nov. is proposed. The type strain is ysch24T (=GDMCC 1.1355T=KACC 21527T).

Novosphingobium silvae sp. nov., isolated from subtropical forest soil.

A novel bacterial strain, designated FGD1T, was isolated from subtropical forest soil of the Nanling National Forest Park located in Guangdong Province, P.R. China. Phylogenetic analyses based on 16S rRNA gene sequences showed that strain FGD1T was most closely related to Novosphingobium lindaniclasticum DSM 25049T (98.8 %), followed by N. barchaimii DSM 25411T (98.7 %), N. guangzhouense DSM 32207T (98.2 %), N. panipatense DSM 22890T (98.1 %) and other species of Novosphingobium (<98 %). The draft genome sequence was 4.58 Mb in length with a G+C content of 65.1 mol%. The calculated average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values between strain FGD1T and closely related type strains were 77.7‒79.6 % and 21.7-22.9 %, respectively. Major fatty acids were summed feature 8 (C18 : 1 ω7c and/or C18 : 1 ω6c), summed feature 3 (C16 : 1 ω7c and/or C16 : 1 ω6c), C14 : 0 2-OH and C16 : 0. The predominant respiratory quinone was ubiquinone 10 and the major polyamine was spermidine. Polar lipids were composed of sphingoglycolipid, phosphatidylglycerol, phosphatidylethanolamine, phosphatidylmethylethanolamine, diphosphatidylglycerol, an unidentified phospholipid and lipid. The polyphasic taxonomic results indicated that strain FGD1T represents a novel species of the genus Novosphingobium, for which the name Novosphingobium silvae sp. nov. is proposed. The type strain is FGD1T (=GDMCC 1.1761T=KACC 21283T).

Methylobacterium nonmethylotrophicum sp. nov., isolated from tungsten mine tailing.

A novel pink-pigmented strain, designated 6HR-1T, was isolated from tungsten mine tailings in Jiangxi Province, PR China. Cells were Gram-stain-negative, aerobic, non-spore-forming, rod-shaped and motile with a polar flagellum (monotrichous). It could not utilize methanol, methylamine, formaldehyde or formate as a sole carbon source. The methanol dehydrogenase mxaF gene was absent but the xoxF gene was present. Phylogenomic and 16S rRNA gene phylogenetic analyses clearly showed that strain 6HR-1T was affiliated to the genus Methylobacterium and closely related to 'Methylobacterium terrae' 17Sr1-28T (98.6 %), Methylobacterium platani JCM 14648T (97.7 %), Methylobacterium variabile DSM 16961T (97.7 %) and Methylobacterium currus KACC 19662T (97.4 %). The average nucleotide identity and digital DNA-DNA hybridization values between strain 6HR-1T and its closely related type species were 87.4-88.7 and 33.2-36.3 %, respectively. It had summed feature 8 (C18 : 1 ω7c and/or C18 : 1 ω6c) as the major fatty acid and ubiquinone 10 as the predominant respiratory quinone. Polyphasic characterization supported that strain 6HR-1T represents a novel species of the genus Methylobacterium, for which the name Methylobacterium nonmethylotrophicum sp. nov. is proposed with the type strain 6HR-1T (=GDMCC 1.662T=KCTC 42760T).