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.

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.

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.

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.

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).

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.

Linking lipid transfer with reduced arbuscule formation in tomato roots colonized by arbuscular mycorrhizal fungus under low pH stress.

Arbuscules are the core structures of arbuscular mycorrhizae (AM), and arbuscule development is regulated by environmental stress, e.g., low pH. Recent studies indicate that lipid transfer from plants is essential for AM fungal colonization; however, the role of lipid transfer in arbuscule formation and the dynamics of lipid accumulation in arbuscules under low pH stress are far from well understood. In the symbiosis of tomato and Rhizophagus intraradices under contrasting pH conditions (pH 4.5 vs. pH 6.5), we investigated arbuscule formation, nutrient uptake, alkaline phosphatase activity and lipid accumulation; examined the gene expression involved in phosphate transport, lipid biosynthesis and transfer and sugar metabolism; and visualized the lipid dynamics in arbuscules. Low pH greatly inhibited arbuscule formation, in parallel with reduced phospholipid fatty acids accumulation in AM fungus and decreased P uptake. This reduction was supported by the decreased expression of plant genes encoding lipid biosynthesis and transfer. More degenerating arbuscules were observed under low pH conditions, and neutral lipid fatty acids accumulated only in degenerating arbuscules. These data reveal that, under low pH stress, reduced lipid transfer from hosts to AM fungi is responsible for the inhibited arbuscule formation.

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.

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).

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).

Transfer of Sphingorhabdus marina, Sphingorhabdus litoris, Sphingorhabdus flavimaris and Sphingorhabdus pacifica corrig. into the novel genus Parasphingorhabdus gen. nov. and Sphingopyxis baekryungensis into the novel genus Novosphingopyxis gen. nov. within the family Sphingomonadaceae.

During a phylogenetic analysis of Sphingorhabdus and its closely related genera in the family Sphingomonadaceae, we found that the genus Sphingorhabdus and the species Sphingopyxis baekryungensis might not be properly assigned in the taxonomy. Phylogenetic, phenotypic and chemotaxonomic characterizations clearly showed that the genus Sphingorhabdus should be reclassified into two genera (Clade I and Clade II), for which the original genus name, Sphingorhabdus, is proposed to be retained only for Clade I, and a new genus named as Parasphingorhabdus gen. nov. is proposed for Clade II with four new combinations: Parasphingorhabdus marina comb. nov., Parasphingorhabdus litoris comb. nov., Parasphingorhabdus flavimaris comb. nov. and Parasphingorhabdus pacifica comb. nov. Moreover, Sphingopyxis baekryungensis should represent a novel genus in the family Sphingomonadaceae, for which the name Novosphingopyxis gen. nov. is proposed, with a combination of Novosphingopyxis baekryungensis comb. nov. The study provides a new insight into the taxonomy of closely related genera in the family Sphingomonadaceae.

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).

Sphingobium paulinellae and Sphingobium algicola Lee and Jeon 2017 are two later heterotypic synonyms of Sphingobium limneticum Chen et al. 2013 and emended description of the species.

Phylogenetic analysis of the genus Sphingobium had shown that the type strains of Sphingobium paulinellae, Sphingobium algicola and Sphingobium limneticum shared a very close relationship between each other. The 16S rRNA gene sequences similarity values between each other ranged from 99.65 to 99.93 %. Whole genome sequencing was performed and genomic relatedness values between each pair of the species were 97.49-100 % (ANI) and 79.3-100 % (dDDH), respectively, all higher than the threshold values of 95-96 % ANI and 70 % dDDH suggested for species discrimination, and implicated that the type strains should belong to the same species of the genus Sphingobium. The phenotypic and chemotaxonomic characterizations performed in the original descriptions of S. paulinellae and S. algicola also supported the same conclusion. Due to priority of publication Sphingobium paulinellae and Sphingobium algicola Lee and Jeon 2017, should be taken as two later heterotypic synonyms of Sphingobium limneticum Chen et al. 2013. Correspondingly, the species description of Sphingobium limneticum was emended based on this study.

Rhizobium glycinendophyticum sp. nov., isolated from roots of Glycine max (Linn. Merr.).

A Gram-stain-negative, rod-shaped and aerobic bacterium, designated CL12T, was isolated from roots of Glycine max (Linn. Merr.) collected from an experimental field in the campus of South China Agricultural University, PR China (22°58'46″S, 110°51'10″E). Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain CL12T belongs to the genus Rhizobium, closely related to Rhizobium wuzhouense W44T (99.3%), followed by Rhizobium rosettiformans W3T (98.0%) and Rhizobium ipomoeae Shin9-1T (97.9%). The results of analysis of sequences of four housekeeping genes (recA, atpD, rpoB and glnA) also revealed strain CL12T to be closely related to R. wuzhouense W44T with the similarities 91.0%, 95.0%, 94.2% and 90.5%, respectively. The major fatty acid of strain CL12T was Summed Feature 8 (C18:1ω7c and/or C18:1ω6c). Strain CL12T had not the nodulation genes (nodC and nodA) and nitrogenase reductase gene (nifH), and could not cause formation of nodule on soybean. The draft genome size of strain CL12T was 4.84 Mbp with a genomic DNA G + C content of 61.1 mol%. The digital DNA-DNA hybridization (dDDH) and average nucleotide identity (ANI) of strain CL12T and R. wuzhouense W44T were 27.4% and 84.7%, respectively. Based on genomic, phenotypic and phylogenetic analysis, strain CL12T is suggested to represent a new species of the genus Rhizobium, for which the name Rhizobium glycinendophyticum sp. nov. is proposed. The type strain is CL12T (=GDMCC 1.1597T = KACC 21281T).

Whole genome sequences reveal the presence of 11 heterotypic synonyms in the genus Sphingobium and emended descriptions of Sphingobium indicum, Sphingobium fuliginis, Sphingobium xenophagum and Sphingobium cupriresistens.

Phylogenetic analysis based on 16S rRNA gene sequences of the genus Sphingobium showed the presence of four distinguishable clusters, in each of which the species shared almost the same evolutionary distance. They were Sphingobium indicum, Sphinogbium lucknowense, Sphinogbium chinhatense, Sphinogbium francense and Sphinogbium japonicum in cluster I, Sphinogbium barthaii and Sphinogbium fuliginis in cluster II, Sphinogbium hydrophobicum and Sphinogbium xenophagum in cluster III and Sphinogbium czechense and Sphinogbium cupriresistens in cluster IV. The 16S rRNA gene sequence similarities between the species in each cluster were all higher than 98 %. Genome-based average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) relatedness values between the species of each cluster were all higher than the threshold values of 95-96 % ANI and 70 % dDDH for species discrimination, respectively, suggesting that each cluster represents only one species of the genus Sphingobium. Due to priority of publication, S. lucknowense, S. chinhatense, S. francense and S. japonicum should be taken as later heterotypic synonyms of S. indicum, S. barthaii as a later heterotypic synonym of S. fuliginis, S. hydrophobicum as a later heterotypic synonym of S. xenophagum and S. czechense as a later heterotypic synonym of S. cupriresistens. Correspondingly, the descriptions of S. indicum, S. fuliginis, S. xenophagum and S. cupriresistens are also emended based on this study.

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

A Gram-stain-negative, rod-shaped and aerobic bacterium, designated K20C18050901T, was isolated from forest soil collected on 11 September 2017 from Dinghushan Biosphere Reserve, Guangdong Province, PR China (23° 10' 24'' N; 112° 32' 10'' E). Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain K20C18050901T belongs to the genus Chitinophaga, and showed the highest similarities to Chitinophaga sancti NBRC 15057T (98.6 %) and Chitinophaga oryziterrae JCM 16595T (96.9 %). The major fatty acids (>10 %) were iso-C15 : 0, C16 : 1ω5c, summed feature 3 (C16 : 1ω6c and/or C16 : 1ω7c) and iso-C17 : 0 3-OH. The predominant respiratory quinone was menaquinone-7. The major polar lipid was phosphatidylethanolamine. The draft genome size of strain K20C18050901T was 8.36 Mb with a DNA G+C content of 44.7 mol%. The digital DNA-DNA hybridization and average nucleotide identity values between strain K20C18050901T and C. sancti NBRC 15057T were 31.40 and 85.82 %, respectively. On the basis of phenotypic, genotypic and phylogenetic analysis, strain K20C18050901T represents a novel species of the genus Chitinophaga, for which the name Chitinophagasilvisoli sp. nov. is proposed. The type strain is K20C18050901T (=GDMCC 1.1411T=KCTC 62860T).

Microvirga flavescens sp. nov., a novel bacterium isolated from forest soil and emended description of the genus Microvirga.

An aerobic, Gram-stain-negative, motile and rod-shaped bacterium, designated c27j1T, was isolated from a forest soil sample from the Chebaling National Nature Reserve in Guangdong Province, China. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain c27j1T belongs to the genus Microvirga and was most closely related to Microvirga aerophila DSM 21344T (97.7 %) and Microvirga subterranea DSM 14364T (96.7 %). The average nucleotide identity and digital DNA-DNA hybridization values based on whole genome sequences of strain c27j1 T and M. aerophila DSM 21344T were 77.2 and 22.4 %, respectively. It contained ubiquinone 10 as the predominant quinone, and C19 : 0 cycloω8c and summed feature 8 (C18 : 1ω7c and/or C18 : 1ω6c) as the major fatty acids. The polar lipids consisted of phosphatidylglycerol, phosphatidylcholine, diphosphatidylglycerol, phosphatidylethanolamine and two unidentified glycolipids. The genomic DNA G+C content based on the whole genome sequence was 62.2 mol%. Phenotypic, chemotaxonomic, phylogenetic and genomic analyses suggested that strain c27j1T should represent a novel species of the genus Microvirga, for which the name Microvirgaflavescens sp. nov. is proposed. The type strain is c27j1T (=GDMCC 1.1356T=KCTC 62433T). The description of the genus Microvirga is also emended, including the major fatty acids, genome size and DNA G+C content.