Water bridges as the trigger in an amino functionalized Zn-MOF for highly selective and sensitive fluorescent sensing of water.

Water is a fundamental element for life. The highly selective and sensitive sensing of water is always attractive for mankind in activities such as physiological processes study and extraterrestrial life exploration. Fluorescent MOFs with precise channels and functional groups might specifically recognize water molecules with hydrogen-bond interaction or coordination effects and work as water sensors. As a proof of concept, herein, an amino functionalized Zn-MOF (named as complex 1) with pores that just right for water molecules to form hydrogen bond bridges is revealed for highly selective and sensitive fluorescent sensing of water. The single-crystal X-ray diffraction analysis indicates that the 3D framework of complex 1 is functionalized with free amino groups in the channels. Hydrogen bonds formed in the channel along b-axis as water bridges to connect two adjacent NH2bdc ligands and result in the restriction of intramolecular motions (RIM) which could responsible for the selective turn-on fluorescence response to water. Complex 1 exhibits high sensitive to trace amount of water in organic solvents and could be used for water detection in a wide range water contents. Take advantages of complex 1, portable sensors (complex 1@PMMA) were prepared and used in the highly sensitive water sensing.

Parachryseolinea silvisoli gen. nov., sp. nov., isolated from forest soil, and reclassification of Chryseolinea flava as Pseudochryseolinea flava gen. nov., comb. nov.

A lemon-chiffon strain, designated QH1ED-6-2T, was isolated from a soil sample collected from Qinghai Virgin Forests, Qinghai Province, PR China. The strain was Gram-stain-negative, aerobic, rod-shaped and motile by gliding. Phylogenetic analysis of 16S rRNA gene sequences revealed that strain QH1ED-6-2T belongs to the family Fulvivirgaceae, and has the highest similarity values of 93.6-92.0 % to Ohtaekwangia koreensis CCUG 58939T, Ohtaekwangia kribbensis CCUG 58938T, Chryseolinea flava SDU1-6T and Chryseolinea serpens DSM 24574T, respectively. The major cellular fatty acids included iso-C15 : 0, C16 : 1 ω5c, iso-C17 : 0 3-OH and summed feature 3. The major polar lipid was phosphatidylethanolamine. The predominant respiratory quinone was menaquinone-7. The average amino acid identity values and percentages of conserved proteins between QH1ED-6-2T and its closely related genera were 66.4-69.6 % and 58.9-64.9 %, respectively, which are interspersed in the intra-genera cutoff values. The digital DNA-DNA hybridization values were 17.6-19.2 %. The draft genome size of strain QH1ED-6-2T was 7.98 Mbp with a DNA G+C content of 51.4 mol%. Based on phenotypic, chemotaxonomic, phylogenetic data, genomic DNA G+C content, as well as AAI, POCP and dDDH results, strain QH1ED-6-2T represents a novel species of a new genus in the family Fulvivirgaceae, for which the name Parachryseolinea silvisoli sp. nov. is proposed. The type strain is QH1ED-6-2T (=GDMCC 1.2318T=JCM 35041T). We also propose the reclassification of Chryseolinea flava as Pseudochryseolinea flava gen. nov., comb. nov. (type strain SDU1-6T=CGMCC 1.13492T=JCM 32520T).

Ruegeria alba sp. nov., Isolated from a Tidal Flat Sediment.

A novel Gram-staining-negative, aerobic, rod-shaped, and white-colored bacterium designated as 1NDH52CT was isolated from a tidal flat sediment and its taxonomic position was determined using a polyphasic taxonomic approach. The microorganism was found to grow at 10-37 °C, pH 6.0-9.0, and in the presence of 0-2% (w/v) NaCl, and to hydrolyze gelatin and aesculin. The major cellular fatty acid of strain 1NDH52CT was summed feature 8 (C19:1 ω7c and/or C18:1 ω6c); the polar lipids comprised diphosphatidylglycerol, phosphatidylcholine, phosphatidylethanolamine, phosphatidylglycerol, an aminolipid, and a lipid; the respiratory quinone was ubiquinone-10. The 16S rRNA gene-based phylogenetic analysis showed that strain 1NDH52CT was closely related to members of the genus Ruegeria with the identity of 98.2% to the type strain Ruegeria pomeroyi DSM 15711T. The genome DNA G + C content of strain 1NDH52CT was 63.6%. The phylogenomic analysis indicated that strain 1NDH52CT formed an independent branch distinct from reference type strains of species within this genus. Digital DNA-DNA hybridization and average nucleotide identity values between strain 1NDH52CT and reference strains were, respectively, 19.1-41.5% and 78.3-91.3%, which are far below the thresholds of 70% and 95-96% for species definition, respectively, indicating that strain 1NDH52CT represents a novel genospecies of the genus Ruegeria. Based on phenotypic and genotypic data, strain 1NDH52CT is concluded to represent a novel species of the genus Ruegeria, for which the name Ruegeria alba sp. nov., is proposed. The type strain of the species is 1NDH52CT (= GDMCC 1.2382T = KCTC 82664T).

Pseudomonas oligotrophica sp. nov., a Novel Denitrifying Bacterium Possessing Nitrogen Removal Capability Under Low Carbon-Nitrogen Ratio Condition.

Pseudomonas is a large and diverse genus within the Gammaproteobacteria known for its important ecological role in the environment. These bacteria exhibit versatile features of which the ability of heterotrophic nitrification and aerobic denitrification can be applied for nitrogen removal from the wastewater. A novel denitrifying bacterium, designated JM10B5aT, was isolated from the pond water for juvenile Litopenaeus vannamei. The phylogenetic, genomic, physiological, and biochemical analyses illustrated that strain JM10B5aT represented a novel species of the genus Pseudomonas, for which the name Pseudomonas oligotrophica sp. nov. was proposed. The effects of carbon sources and C/N ratios on denitrification performance of strain JM10B5aT were investigated. In addition, the results revealed that sodium acetate was selected as the optimum carbon source for denitrification of this strain. Besides, strain JM10B5aT could exhibit complete nitrate removal at the low C/N ratio of 3. Genomic analyses revealed that JM10B5aT possessed the functional genes including napA, narG, nirS, norB, and nosZ, which might participate in the complete denitrification process. Comparative genomic analyses indicated that many genes related to aggregation, utilization of alkylphosphonate and tricarballylate, biosynthesis of cofactors, and vitamins were contained in the genome of strain JM10B5aT. These genomic features were indicative of its adaption to various niches. Moreover, strain JM10B5aT harbored the complete operons required for the biosynthesis of vibrioferrin, a siderophore, which might be conducive to the high denitrification efficiency of denitrifying bacterium at low C/N ratio. Our findings demonstrated that the strain JM10B5aT could be a promising candidate for treating wastewater with a low C/N ratio.

Engineering a Balanced Acetyl Coenzyme A Metabolism in Saccharomyces cerevisiae for Lycopene Production through Rational and Evolutionary Engineering.

Saccharomyces cerevisiae is increasingly being used for the production of chemicals derived from acetyl coenzyme A (acetyl-CoA). However, the inadequate supply of cytosolic acetyl-CoA often leads to low yields. Here, we developed a novel strategy for balancing acetyl-CoA metabolism and increasing the amount of the downstream product. First, the combination of acetaldehyde dehydrogenase (eutE) and acetoacetyl-CoA thiolase (AtoB) was optimized to redirect the acetyl-CoA flux toward the target pathway, with a 21-fold improvement in mevalonic acid production. Second, pathway engineering and evolutionary engineering were conducted to attenuate the growth deficiency, and a 10-fold improvement of the maximum productivity was achieved. Third, acetyl-CoA carboxylase (ACC1) was dynamically downregulated as the complementary acetyl-CoA pathway, and the yield was improved more than twofold. Fourth, the most efficient and complementary acetyl-CoA pathways were combined, and the final strain produced 68 mg/g CDW lycopene, which was among the highest yields reported in S. cerevisiae. This study demonstrates a new method of producing lycopene products by regulating acetyl-CoA metabolism.

Shewanella jiangmenensis sp. nov., isolated from aquaculture water.

A Gram-stain-negative and facultatively anaerobic bacterial strain designated as JM162201T was isolated from aquaculture water for farming Pacific white shrimp (Litopenaeus vannamei). The genome size of strain JM162201T was 4,436,316 bp, and the genomic DNA G + C content was 55.0%. Phylogenetic analysis based on 16S rRNA gene sequences and genomes showed that strain JM162201T belonged to the genus Shewanella and was closely related to Shewanella litorisediminis SMK1-12T (97.1%), Shewanella khirikhana TH2012T (97.0%), and Shewanella amazonensis SB2BT (96.0%). The average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values between strain JM162201T and three reference type strains were below the recognized thresholds of 95.0-96.0% (for ANI) and 70.0% (for dDDH) for species delineation. Growth occurred at 10-40 °C (optimum, 30 °C), at pH 4.0-10.0 (optimum, 7.0-8.0), and in 0-6.0% NaCl (w/v, optimum, 0-0.1%). The major cellular fatty acids of strain JM162201T were summed feature 3 (C16:1 ω7c and/or C16:1 ω6c), C17:1 ω8c, iso-C15:0, C16:0, and C15:0. The predominant quinones were MK7, Q-7, and Q-8. The major polar lipids were phosphatidylethanolamine (PE) and phosphatidylglycerol (PG). Based on the polyphasic taxonomical analyses, strain JM162201T represents a novel species of the genus Shewanella, for which the name Shewanella jiangmenensis sp. nov. is proposed, with the type strain JM162201T (= GDMCC 1.2006T = KCTC 82340T).

Flavobacterium proteolyticum sp. nov., isolated from aquaculture water.

A novel aerobic, yellow, and rod-shaped bacterial isolate, designated as 1Y8AT, was isolated from aquaculture water sampled in Jiangmen, Guangdong province, P. R. China. Here, the taxonomic position of strain 1Y8AT was conducted based on phenotypic, genomic, and chemotaxonomic characteristics. Strain 1Y8AT was observed to grow at 10-37 °C (optimum 28 °C), at pH 6.0-9.0 (optimum 7.0) and in 0-2% NaCl (optimum 1%, w/v). The 16S rRNA gene-based analysis showed that strain 1Y8AT was closely related to "Flavobacterium sasangense" YC6274T (99.3%), Flavobacterium aquaticum JC164T (98.4%), Flavobacterium cucumis R2A45-3T (98.0%), Flavobacterium celericrescens TWA-26T (98.0%), and Flavobacterium cheniae NJ-26T (97.2%). The digital DNA-DNA hybridization (dDDH) and average nucleotide identity (ANI) values between strain 1Y8AT and reference strains above were far below the recognized thresholds of 70% dDDH and 95-96% ANI for species definition, implying that the strain represents a novel genospecies. The phylogenomic analysis indicated that strain 1Y8AT formed an independent branch distinct from known species. The major cellular fatty acids of strain 1Y8AT were iso-C15:0, iso-C15:1 G and C15:0; the polar lipids comprised phosphatidylethanolamine, glycolipid, and two lipids; the respiratory quinone was MK-6. The G + C content of genomic DNA was 32.5%. Based on the genotypic and phenotypic characteristics such as the utilization of D-glucose and casein hydrolysis, strain 1Y8AT is concluded to represent a novel species of the genus Flavobacterium, for which the name Flavobacterium proteolyticum sp. nov. is proposed. The type strain of the species is 1Y8AT (= GDMCC 1.1933T = KACC 22081T).

Upstream Activation Sequence Can Function as an Insulator for Chromosomal Regulation of Heterologous Pathways Against Position Effects in Saccharomyces cerevisiae.

Metabolic engineering of microbial cell factories through integrating the heterologous synthetic pathway into the chromosome is most commonly used for industrial applications. However, the position of the foreign gene in the chromosome can affect its transcriptional level. As a microorganism that is generally regarded as safe (GRAS) and commonly applied in industrial manufacture with large-scale operations, Saccharomyces cerevisiae is also confronted with this position effect. In this study, we characterized 12 different chromosome sites by inserting the lycopene biosynthetic pathway as a reporter cassette. Due to the different integration loci, the gene transcription and lycopene yield exhibited more than 58-fold and 3.8-fold differences, respectively. Furthermore, changing the gene order also revealed a remarkable influence (30-fold and 14-fold) on gene transcription and lycopene yield. Besides, the upstream activation sequence of a strong promoter (defined as an insulator) in S. cerevisiae could reduce the impact by gene order, and increased the gene transcription (tenfold) and lycopene yield (sevenfold). Taken together, our results demonstrated that gene order and insulator affected gene transcription and heterogeneous biosynthesis, opening the opportunity to regulate gene transcription by insulator against position effect in S. cerevisiae.

Sphingobacterium micropteri sp. nov. and Sphingobacterium litopenaei sp. nov., isolated from aquaculture water.

Two novel bacterial strains, designated as DN00404T and DN04309T, were isolated from aquaculture water and characterized by using a polyphasic taxonomic approach. Cells of strains DN00404T and DN04309T were Gram-stain-negative, aerobic, non-motile, oxidase-positive and catalase-positive. Cells of DN00404T were short rod-shaped and those of DN04309T were long rod-shaped. Strain DN00404T was found to grow at 15-37 °C (optimum, 25-30 °C), at pH 6.0-11.0 (optimum, pH 7.5) and in 0-2.0 % (w/v) NaCl (optimum, 1.0 %). Strain DN04309T was found to grow at 15-45 °C (optimum, 20-37 °C), at pH 5.5-11.0 (optimum, 7.5) and in 0-4.0 % (w/v) NaCl (optimum, 0.5 %). Phylogenetic analyses based on 16S rRNA gene and genome sequences revealed that the two strains belonged to the genus Sphingobacterium and were distinct from all known species of this genus. The average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values between the two strains and between each of the two strains and related type strains of this genus were well below the recognized thresholds of 95.0-96.0 % ANI and 70.0 % dDDH for species delineation. The genomic DNA G+C contents of strains DN00404T and DN04309T were 41.6 and 36.0 mol%, respectively. The respiratory quinone in both strains was identified as MK-7, and their major fatty acids were iso-C15 : 0 and summed feature 3 (C16 : 1 ω6c and/or C16 : 1 ω7c), which were similar to those of other species of this genus. The two major fatty acids C16 : 0 and iso-C17 : 0 3-OH were also found in strain DN00404T. Based on genotypic and phenotypic characteristics, two novel species of the genus Sphingobacterium are proposed: Sphingobacterium micropteri sp. nov. with DN00404T (=GDMCC 1.1865T=KACC 21924T) as the type strain and Sphingobacterium litopenaei sp. nov. with DN04309T (=GDMCC 1.1984T=KCTC 82348T) as the type strain.

Transcriptome Analysis Reveals a Promotion of Carotenoid Production by Copper Ions in Recombinant Saccharomyces cerevisiae.

We previously constructed a Saccharomyces cerevisiae carotenoid producer BL03-D-4 which produced much more carotenoid in YPM (modified YPD) media than YPD media. In this study, the impacts of nutritional components on carotenoid accumulation of BL03-D-4 were investigated. When using YPM media, the carotenoid yield was increased 10-fold compared to using the YPD media. To elucidate the hidden mechanism, a transcriptome analysis was performed and showed that 464 genes changed significantly in YPM media. Furthermore, inspired by the differential gene expression analysis which indicated that ADY2, HES1, and CUP1 showed the most remarkable changes, we found that the improvement of carotenoid accumulation in YPM media was mainly due to the copper ions, since supplementation of 0.08 mM CuSO4 in YPD media could increase carotenoid yield 9.2-fold. Reverse engineering of target genes was performed and carotenoid yield could be increased 6.4-fold in YPD media through overexpression of ACE1. The present study revealed for the first time the prominent promotion of carotenoid yield by copper ions in engineered S. cerevisiae and provided a new target ACE1 for genetic engineering of S. cerevisiae for the bioproduction of carotenoids.

Myxococcus xanthus R31 Suppresses Tomato Bacterial Wilt by Inhibiting the Pathogen Ralstonia solanacearum With Secreted Proteins.

The pathogenic bacterium Ralstonia solanacearum caused tomato bacterial wilt (TBW), a destructive soil-borne disease worldwide. There is an urgent need to develop effective control methods. Myxobacteria are microbial predators and are widely distributed in the soil. Compared with other biocontrol bacteria that produce antibacterial substances, the myxobacteria have great potential for biocontrol. This study reports a strain of Myxococcus xanthus R31 that exhibits high antagonistic activity to R. solanacearum. Plate test indicated that the strain R31 efficiently predated R. solanacearum. Pot experiments showed that the biocontrol efficacy of strain R31 against TBW was 81.9%. Further study found that the secreted protein precipitated by ammonium sulfate had significant lytic activity against R. solanacearum cells, whereas the ethyl acetate extract of strain R31 had no inhibitory activity against R. solanacearum. Substrate spectroscopy assay and liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis of secreted proteins showed that some peptidases, lipases, and glycoside hydrolases might play important roles and could be potential biocontrol factors involved in predation. The present study reveals for the first time that the use of strain M. xanthus R31 as a potential biocontrol agent could efficiently control TBW by predation and secreting extracellular lyase proteins.

Identification of a novel metabolic engineering target for carotenoid production in Saccharomyces cerevisiae via ethanol-induced adaptive laboratory evolution.

Carotenoids are a large family of health-beneficial compounds that have been widely used in the food and nutraceutical industries. There have been extensive studies to engineer Saccharomyces cerevisiae for the production of carotenoids, which already gained high level. However, it was difficult to discover new targets that were relevant to the accumulation of carotenoids. Herein, a new, ethanol-induced adaptive laboratory evolution was applied to boost carotenoid accumulation in a carotenoid producer BL03-D-4, subsequently, an evolved strain M3 was obtained with a 5.1-fold increase in carotenoid yield. Through whole-genome resequencing and reverse engineering, loss-of-function mutation of phosphofructokinase 1 (PFK1) was revealed as the major cause of increased carotenoid yield. Transcriptome analysis was conducted to reveal the potential mechanisms for improved yield, and strengthening of gluconeogenesis and downregulation of cell wall-related genes were observed in M3. This study provided a classic case where the appropriate selective pressure could be employed to improve carotenoid yield using adaptive evolution and elucidated the causal mutation of evolved strain.

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.

Long-Term Effect against Methicillin-Resistant Staphylococcus aureus of Emodin Released from Coaxial Electrospinning Nanofiber Membranes with a Biphasic Profile.

Methicillin-resistant Staphylococcus aureus (MRSA) is a serious and rapidly growing threat to human beings. Emodin has a potent activity against MRSA; however, its usage is limited due to high hydrophobicity and low oral bioavailability. Thus, the coaxial electrospinning nanofibers encapsulating emodin in the core of hydrophilic poly (vinylpyrrolidone), with a hygroscopic cellulose acetate sheath, have been fabricated to provide long-term effect against MRSA. Scanning electron microscopy and transmission electron microscopy confirmed the nanofibers had a linear morphology with nanometer in diameter, smooth surface, and core-shell structure. Attenuated total reflection-Fourier transform infrared spectra, X-ray diffraction patterns, and differential scanning calorimetric analyses verified emodin existed in amorphous form in the nanofibers. The nanofibers have 99.38 ± 1.00% entrapment efficiency of emodin and 167.8 ± 0.20 % swelling ratio. Emodin released from nanofibers showed a biphasic drug release profile with an initial rapid release followed by a slower sustained release. CCK-8 assays confirmed the nontoxic nature of the emodin-loaded nanofibers to HaCaT cells. The anti-MRSA activity of the nanofibers can persist up to 9 days in AATCC147 and soft-agar overlay assays. These findings suggest that the emodin-loaded electrospun nanofibers with core-shell structure could be used as topical drug delivery system for wound infected by MRSA.

Marinobacter denitrificans sp. nov., isolated from marine sediment of southern Scott Coast, Antarctica.

A novel bacterium, designated JB02H27T, was isolated from marine sediment collected from the southern Scott Coast, Antarctica. Cells were Gram-stain-negative, facultatively anaerobic, polar-flagellated and motile rods. Growth occurred at 4-45 °C, at pH 7.0-9.0 and with 3-25 % (w/v) NaCl. Phylogenetic trees based on 16S rRNA gene sequences showed that strain JB02H27T consistently fell within the genus Marinobacter and formed a clade together with Marinobacter algicola DG893T (98.8 % similarity), Marinobacter confluentis KCTC 42705T (98.4 %), Marinobacter salarius R9SW1T (98.4%) and Marinobacter halotolerans CP12T (97.9 %), which were subsequently used as reference strains for comparisons of phenotypic and chemotaxonomic characteristics. Average nucleotide identity values between strain JB02H27T and the four related type strains were 80.9, 76.6, 81.9 and 76.3 %, respectively. The major fatty acids were summed feature 3, C16 : 0, C18 : 1 ω9c and C16 : 0 N alcohol. The polar lipids included phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, and an unidentified phospholipid, aminolipid, aminophospholipid and glycolipids. The sole respiratory quinone was ubiquinone-9. The DNA G+C content was 56.9 mol%. Based on the genomic, phylogenetic, phenotypic and chemotaxonomic analysis, we propose that strain JB02H27T represents a novel species of the genus Marinobacter, for which the name Marinobacter denitrificans sp. nov. is proposed. The type strain is JB02H27T (=GDMCC 1.1528T=KCTC 62941T).

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.

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).

Pseudidiomarina gelatinasegens sp. nov., isolated from surface sediment of the Terra Nova Bay, Antarctica.

Polyphasic taxonomic analysis was performed to characterize a novel bacterium, which was isolated from surface sediment of the Terra Nova Bay, Antarctica, and designated as R04H25T. The cells of the isolate were Gram-stain-negative, aerobic, non-motile, slightly curved rods. Growth occurred at 4-42 °C, pH 7.0-9.5, and in 1-15 % (w/v) NaCl. Phylogenetic trees based on 16S rRNA gene sequences indicated that strain R04H25T formed an independent lineage within the genus Pseudidiomarina and its nearest neighbours were Pseudidiomarina donghaiensis 908033T (98.2 %), Pseudidiomarina marina PIM1T (98.1 %), Pseudidiomarina woesei W11T (97.8 %), Pseudidiomarina maritima 908087T (97.1 %) and Pseudidiomarina tainanensis PIN1T (97.0 %). The average nucleotide identities between strain R04H25T and the nearest neighbours were 76.2-77.7 %. The major fatty acids were iso-C17 : 0, summed feature 9, iso-C15 : 0, C16 : 0 and iso-C11 : 0 3-OH. The polar lipids comprised phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, an unidentified aminophospholipid, three unidentified glycolipids and two unidentified lipids. The predominant respiratory quinone was ubiquinone 8. The genomic DNA G+C content was 48.2 mol%. On the basis of the phylogenetic, physiological and chemotaxonomic results, we propose a novel species named as Pseudidiomarina gelatinasegens sp. nov. in the genus Pseudidiomarina, with the type strain R04H25T (=GDMCC 1.1503T=KCTC 62911T).

Culture-Dependent and -Independent Analyses Reveal the Diversity, Structure, and Assembly Mechanism of Benthic Bacterial Community in the Ross Sea, Antarctica.

The benthic bacterial community in Antarctic continental shelf ecosystems are not well-documented. We collected 13 surface sediments from the Ross Sea, a biological hotspot in high-latitude maritime Antarctica undergoing rapid climate change and possible microflora shift, and aimed to study the diversity, structure and assembly mechanism of benthic bacterial community using both culture-dependent and -independent approaches. High-throughput sequencing of 16S rRNA gene amplicons revealed 370 OTUs distributed in 21 phyla and 284 genera. The bacterial community was dominated by Bacteroidetes, Gamma- and Alphaproteobacteria, and constituted by a compact, conserved and positively-correlated group of anaerobes and other competitive aerobic chemoheterotrophs. Null-model test based on ßNTI and RCBray indicated that stochastic processes, including dispersal limitation and undominated fractions, were the main forces driving community assembly. On the other hand, environmental factors, mainly temperature, organic matter and chlorophyll, were significantly correlated with bacterial richness, diversity and community structure. Moreover, metabolic and physiological features of the prokaryotic taxa were mapped to evaluate the adaptive mechanisms and functional composition of the benthic bacterial community. Our study is helpful to understand the structural and functional aspects, as well as the ecological and biogeochemical role of the benthic bacterial community in the Ross Sea.

Deminuibacter soli gen. nov., sp. nov., isolated from forest soil, and reclassification of Filimonas aurantiibacter as Arvibacter aurantiibacter comb. nov.

A novel strain, designated K23C18032701T, was isolated from a sample of forest soil collected from Dinghushan Biosphere Reserve, Guangdong Province, PR China. The strain was Gram-stain-negative, aerobic, motile and showed a shape change from a filamentous cell to coccobacilli. Phylogenetic analysis based on 16S rRNA gene sequences revealed that the novel strain belongs to the family Chitinophagaceae, and showed the highest similarities to Arvibacter flaviflagrans JCM 31293T (95.0 %) and Filimonas aurantiibacter LMG 29039T (94.4 %). The major cellular fatty acids included iso-C15 : 0, iso-C17 : 0 3-OH and iso-C15 : 1 G. The predominant polar lipid was phosphatidylethanolamine (PE). The predominant respiratory quinone was menaquinone-7. The major polyamine was sym-homospermidine. The draft genome size of strain K23C18032701T was 5.84 Mb with a DNA G+C content of 47.2 mol%. Based on phenotypic, genotypic and phylogenetic analysis, strain K23C18032701T represents a novel species of a new genus in the family Chitinophagaceae, for which the name Deminuibacter soli is proposed. The type strain is K23C18032701T (=GDMCC 1.1403T=KCTC 62913T). We also propose the reclassification of Filimonas aurantiibacter as Arvibacter aurantiibacter comb. nov. (type strain 1458T=NRRL B-65305T=LMG 29039T).