Description and Genomic Characteristics of Diaphorobacter limosus sp. nov., Isolated from a Sewage-Treatment Plant.

A Gram-stain-negative, rod-shaped, non-motile, catalase-positive, denitrifying bacterium, designated strain Y-1T, was isolated from an aeration tank of a sewage treatment plant in China and characterized using polyphasic taxonomic approaches. Strain Y-1T could grow at 10-37 °C (optimum 25 °C), at pH 5.0-10.0 (optimum 7.0) and in the presence of 0-3.0% (w/v) NaCl (optimum 0.5%). The phylogenetic tree based on the 16S rRNA gene sequences revealed that strain Y-1T was a member of genus Diaphorobacter, and showed the highest sequence similarities with Diaphorobacter oryzae RF3T (97.50%), Diaphorobacter nitroreducens NA10BT (97.38%) and Diaphorobacter aerolatus 8604S-37T (96.56%). In terms of carbon source utilization and enzyme activities, strain Y-1T was significantly different from its similar strains. The major respiratory quinone was Q-8, and the main polar lipid was phosphatidylethanolamine. Comparative genomic analysis of strain Y-1T and other Diaphorobacter species was conducted to explore the mechanisms underlying the differences among these strains. Strain Y-1T encoded 3957 genes, consisting of 3813 protein-coding genes and 144 RNA coding genes, and encoded 652 enzymes with 31 unique enzymes compared with other related species. The DNA G + C content was 69.95 mol%. Strain Y-1T exhibited 41.71% DNA-DNA relatedness and 95% ANIb with the most related type strains.On the basis of the evidence presented from polyphasic analysis, strain Y-1T was suggested as a novel species within the genus Diaphorobacter, for which the name Diaphorobacter limosus sp. nov. is proposed, with the type strain Y-1T (= KCTC 92852T = CCTCC AB 2023032T).

Acidovorax citrulli Effector AopV Suppresses Plant Immunity and Interacts with Aromatic Dehydratase ADT6 in Watermelon.

Bacterial fruit blotch (BFB) is a disease of cucurbit plants caused by Acidovorax citrulli. Although A. citrulli has great destructive potential, the molecular mechanisms of pathogenicity of A. citrulli are not clear, particularly with regard to its type III secreted effectors. In this study, we characterized the type III secreted effector protein, AopV, from A. citrulli strain Aac5. We show that AopV significantly inhibits reactive oxygen species and the expression of PTI marker genes, and helps the growth of Pseudomonas syringae D36E in Nicotiana benthamiana. In addition, we found that the aromatic dehydratase ADT6 from watermelon was a target of AopV. AopV interacts with ADT6 in vivo and in vitro. Subcellular localization indicated ADT6 and AopV were co-located at the cell membrane. Together, our results reveal that AopV suppresses plant immunity and targets ADT6 in the cell membrane. These findings provide an new characterization of the molecular interaction of A. citrulli effector protein AopV with host cells.

A Single Bacterium Capable of Oxidation and Reduction of Iron at Circumneutral pH.

Fe(II)-oxidizing microorganisms and Fe(III)-reducing microorganisms, which drive the biogeochemical Fe cycle on the Earth's surface, are phylogenetically and ecologically diverse. However, no single organism capable of aerobic Fe(II) oxidation and anaerobic Fe(III) reduction at circumneutral pH have been reported so far. Here, we report a novel neutrophilic Fe(II)-oxidizing Rhodoferax bacterium, strain MIZ03, isolated from an iron-rich wetland in Japan. Our cultivation experiments demonstrate that MIZ03 represents a much more versatile metabolism for energy acquisition than previously recognized in the genus Rhodoferax. MIZ03 can grow chemolithoautotrophically at circumneutral pH by oxidation of Fe(II), H2, or thiosulfate as the sole electron donor under (micro)aerobic conditions (i.e., using O2 as the sole electron acceptor). In addition, it can reduce Fe(III) or nitrate under anaerobic conditions. Thus, this is the first report demonstrating the presence of a single bacterium capable of both Fe(II) oxidation and Fe(III) reduction at circumneutral pH. The observed physiology was consistent with its 4.9-Mbp complete genome encoding key genes for iron oxidation/reduction (foxEY and mtrABC), for nitrate reduction (narGHI), for thiosulfate oxidation (soxABCDXYZ), and for carbon fixation via the Calvin cycle. Our metagenomic survey suggests that there are more Rhodoferax members capable of Fe(II) oxidation and Fe(III) reduction. Such bifunctional Rhodoferax may have an ecological advantage in suboxic/anoxic environments at circumneutral pH by recycling of Fe as the electron donor and acceptor. IMPORTANCE The biogeochemical cycle of iron (Fe) via reactions of oxidation, reduction, precipitation, and dissolution is involved in the cycle of other ecologically relevant elements, such as C, N, P, S, As, Co, Ni, and Pb. The Fe cycle on the Earth's surface is driven by a variety of Fe(II)-oxidizing microorganisms and Fe(III)-reducing microorganisms. Here, we discovered a novel bacterium, Rhodoferax sp. strain MIZ03, capable of both Fe(II) oxidation and Fe(III) reduction at circumneutral pH, and we report its physiological characteristics and complete genome sequence. The unexpected capability of this bacterium provides novel insights into the Fe cycle in the environment. Moreover, this bacterium will help to better understand the molecular mechanisms of microbial Fe redox cycling as a model organism.

Identification and Functional Analysis of AopN, an Acidovorax Citrulli Effector that Induces Programmed Cell Death in Plants.

Bacterial fruit blotch (BFB), caused by Acidovorax citrulli, seriously affects watermelon and other cucurbit crops, resulting in significant economic losses. However, the pathogenicity mechanism of A. citrulli is not well understood. Plant pathogenic bacteria often suppress the plant immune response by secreting effector proteins. Thus, identifying A. citrulli effector proteins and determining their functions may improve our understanding of the underlying pathogenetic mechanisms. In this study, a novel effector, AopN, which is localized on the cell membrane of Nicotiana benthamiana, was identified. The functional analysis revealed that AopN significantly inhibited the flg22-induced reactive oxygen species burst. AopN induced a programmed cell death (PCD) response. Unlike its homologous protein, the ability of AopN to induce PCD was dependent on two motifs of unknown functions (including DUP4129 and Cpta_toxin), but was not dependent on LXXLL domain. More importantly, the virulence of the aopN mutant of A. citrulli in N. benthamiana significantly decreased, indicating that it was a core effector. Further analysis revealed that AopN interacted with watermelon ClHIPP and ClLTP, which responds to A. citrulli strain Aac5 infection at the transcription level. Collectively, these findings indicate that AopN suppresses plant immunity and activates the effector-triggered immunity pathway.

Reassembly of the Biosynthetic Gene Cluster Enables High Epothilone Yield in Engineered Schlegelella brevitalea.

Epothilones, as a new class of microtubule-stabilizing anticancer drugs, exhibit strong bioactivity against taxane-resistant cells and show clinical activity for the treatment of advanced breast cancer. Additionally, they also show great potential for a central nervous system injury and Alzheimer's disease. However, due to the long fermentation period of the original producer and challenges of genetic engineering of nonribosomal peptide/polyketide (NRP/PK) megasynthase genes, the application of epothilones is severely limited. Here, we addressed these problems by reassembling a novel 56-kb epothilone biosynthetic gene cluster, optimizing the promoter of each gene based on RNA-seq profiling, and completing precursor synthetic pathways in engineered Schlegella brevitalea. Furthermore, we debottlenecked the cell autolysis by optimizing culture conditions. Finally, the yield of epothilones in shake flasks was improved to 82 mg/L in six-day fermentation. Overall, we not only constructed epothilone overproducers for further drug development but also provided a rational strategy for high-level NRP/PK compound production.

Show me your secret(ed) weapons: a multifaceted approach reveals a wide arsenal of type III-secreted effectors in the cucurbit pathogenic bacterium Acidovorax citrulli and novel effectors in the Acidovorax genus.

The cucurbit pathogenic bacterium Acidovorax citrulli requires a functional type III secretion system (T3SS) for pathogenicity. In this bacterium, as with Xanthomonas and Ralstonia spp., an AraC-type transcriptional regulator, HrpX, regulates expression of genes encoding T3SS components and type III-secreted effectors (T3Es). The annotation of a sequenced A. citrulli strain revealed 11 T3E genes. Assuming that this could be an underestimation, we aimed to uncover the T3E arsenal of the A. citrulli model strain, M6. Thorough sequence analysis revealed 51 M6 genes whose products are similar to known T3Es. Furthermore, we combined machine learning and transcriptomics to identify novel T3Es. The machine-learning approach ranked all A. citrulli M6 genes according to their propensity to encode T3Es. RNA-Seq revealed differential gene expression between wild-type M6 and a mutant defective in HrpX: 159 and 28 genes showed significantly reduced and increased expression in the mutant relative to wild-type M6, respectively. Data combined from these approaches led to the identification of seven novel T3E candidates that were further validated using a T3SS-dependent translocation assay. These T3E genes encode hypothetical proteins that seem to be restricted to plant pathogenic Acidovorax species. Transient expression in Nicotiana benthamiana revealed that two of these T3Es localize to the cell nucleus and one interacts with the endoplasmic reticulum. This study places A. citrulli among the 'richest' bacterial pathogens in terms of T3E cargo. It also revealed novel T3Es that appear to be involved in the pathoadaptive evolution of plant pathogenic Acidovorax species.

Simplicispira hankyongi sp. nov., a novel denitrifying bacterium isolated from sludge.

A Gram-stain-negative, facultatively anaerobic, motile, light-yellow, and rod-shaped bacterium, designated as NY-02T, was isolated from the sludge of a wastewater treatment plant in Hanam City, Republic of Korea. The comparison of 16S rRNA gene sequences revealed that the strain formed a distinct lineage within the genus Simplicispira and was most closely related to S. suum SC1-8T (99.0%), S. limi EMB325T (98.3%), S. psychrophila LMG 5408T (98.2%), and S. piscis RSG39T (97.4%). Both average nucleotide identity (ANI) and DNA-DNA hybridization (DDH) values between strain NY-02T, and its closes type strains [S. suum SC1-8T, S. limi EMB325T, S. psychrophila LMG 5408T, and S. piscis RSG39T] were lower than the cut-off (≥ 95-96% for ANI and ≥ 70% for DDH) to define a bacterial species. The genome comprises of 3,709,074 bp with a G + C content of 64.2 mol%. Ubiquinone 8 (Q-8) was the predominant quinone. The major fatty acids were C16:0 and summed feature 3 (C16:1ω7c and/or C16:1ω6c), and the major polar lipids were phosphatidylglycerol, diphosphatidylglycerol, and phosphatidylethanolamine. The results of the physiological, biochemical, and taxonomic analyses in addition to low ANI and DNA-DNA relatedness values (82.2% and < 34.0%, respectively) indicate that the strain NY-02T represents a novel species of the genus Simplicispira. The name proposed for strain NY-02T (= KACC 19731T = LMG 31165T) is Simplicispira hankyongi sp. nov.

Ottowia flava sp. nov., isolated from fish intestines.

A novel Gram-negative bacterium, non-motile and short rod-shaped, designated strain GY511T, was isolated from the intestines of fish collected from Maowei Sea, China. Growth occurred at pH 6.0-9.0 (optimum 7.0), 4-37 °C (optimum 28 °C) and at 0-2.5% (w/v) NaCl (optimum 1.0%). The result of 16S rRNA gene sequence analysis showed that strain GY511T is closely related to O. oryzae NBRC 113109T (97.6%), O. konkukae DSM 105395T (97.4%), Ottowia beijingensis CGMCC 1.12324T (95.9%), Ottowia pentelensis DSM 21699T (95.2%) and Ottowia thiooxydans DSM 14619T (95.0%). The DNA-DNA hybridization values of strain GY511T with O. oryzae NBRC 113109T and O. konkukae DSM 105395T were 35.4 ± 3.1% and 26.3 ± 1.8%, respectively. The major fatty acids (> 10%) were identified as summed feature 3 (C16:1ω7c and/or C16:1ω6c), C16:0 and summed feature 8 (C18:1ω7c and/or C18:1ω6c) and the major respiratory quinone was ubiquinone-8 (Q-8). The polar lipids comprised diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, phosphatidylmethylethanolamine, two unidentified aminolipids and an unidentified phospholipid. The G+C content of the genomic DNA was 62.9 mol%. Thiosulfate could be utilized as co-substrate for aerobic growth and was oxidised to sulfate. On the basis of phenotypic, chemotaxonomic and molecular data, strain GY511T is considered to represent a novel species of the genus Ottowia, for which the name Ottowia flava sp. nov. is proposed. The type strain is GY511T (= NBRC 113500T = DSM 107425T = CGMCC 1.13650T).

Gene Expansion and Positive Selection as Bacterial Adaptations to Oligotrophic Conditions.

We examined the genomic adaptations of prevalent bacterial taxa in a highly nutrient- and ion-depleted freshwater environment located in the secondary cooling water system of a nuclear research reactor. Using genome-centric metagenomics, we found that none of the prevalent bacterial taxa were related to typical freshwater bacterial lineages. We also did not identify strong signatures of genome streamlining, which has been shown to be one of the ecoevolutionary forces shaping the genome characteristics of bacterial taxa in nutrient-depleted environments. Instead, focusing on the dominant taxon, a novel Ramlibacter sp. which we propose to name Ramlibacter aquaticus, we detected extensive positive selection on genes involved in phosphorus and carbon scavenging pathways. These genes were involved in the high-affinity phosphate uptake and storage into polyphosphate granules, metabolism of nitrogen-rich organic matter, and carbon/energy storage into polyhydroxyalkanoate. In parallel, comparative genomics revealed a high number of paralogs and an accessory genome significantly enriched in environmental sensing pathways (i.e., chemotaxis and motility), suggesting extensive gene expansions in R. aquaticus The type strain of R. aquaticus (LMG 30558T) displayed optimal growth kinetics and productivity at low nutrient concentrations, as well as substantial cell size plasticity. Our findings with R. aquaticus LMG 30558T demonstrate that positive selection and gene expansions may represent successful adaptive strategies to oligotrophic environments that preserve high growth rates and cellular productivity.IMPORTANCE By combining a genome-centric metagenomic approach with a culture-based approach, we investigated the genomic adaptations of prevalent populations in an engineered oligotrophic freshwater system. We found evidence for widespread positive selection on genes involved in phosphorus and carbon scavenging pathways and for gene expansions in motility and environmental sensing to be important genomic adaptations of the abundant taxon in this system. In addition, microscopic and flow cytometric analysis of the first freshwater representative of this population (Ramlibacter aquaticus LMG 30558T) demonstrated phenotypic plasticity, possibly due to the metabolic versatility granted by its larger genome, to be a strategy to cope with nutrient limitation. Our study clearly demonstrates the need for the use of a broad set of genomic tools combined with culture-based physiological characterization assays to investigate and validate genomic adaptations.

Ottowia konkukae sp. nov., isolated from rotten biji (tofu residue).

A Gram-negative, aerobic, non-motile, non-spore-forming and rod-shaped bacterial strain, designated SK3863T, was isolated from rotten biji (residue remaining after making tofu). This bacterium was characterized in order to determine its taxonomic position by using the polyphasic approach. Strain SK3863T grew well at 25-37 °C on Reasoner's 2A agar plates. On the basis of 16S rRNA gene sequence similarity, strain SK3863T belonged to the family Comamonadaceae and was related to Ottowia beijingensis GCS-AN-3T (96.5 % sequence similarity) and Ottowia pentelensis RB3-7T (96.4 %). Lower sequence similarities (96.2 %) were found to all of the other recognized members of the genus Ottowia. The G+C content of the genomic DNA was 65.8 mol%. The major respiratory lipoquinone was ubiquinone 8 and the major fatty acids were C16 : 1ω6c/C16 : 1ω7c, C16 : 0 and C18 : 1ω7c/C18 : 1ω6c. Strain SK3863T could be differentiated genotypically and phenotypically from the recognized species of the genus Ottowia. The isolate therefore represents a novel species, for which the name Ottowia konkukae sp. nov. is proposed, with the type strain SK3863T (=KCCM 43236T=DSM 105395T).

Ottowia oryzae sp. nov., isolated from Andong sikhye, a Korean traditional rice beverage.

A Gram-stain-negative, non-spore-forming, non-motile, short-rod-shaped bacterial strain, designated KADR8-3T, isolated from Andong sikhye in Andong-si, Gyeongsangbuk-do, Republic of Korea, was characterized using a polyphasic approach. On the basis of morphological, genetic and chemotaxonomic characteristics, it was determined to belong to the genus Ottowia. The phylogenetic similarity based on the 16S rRNA gene sequences indicated the strain formed a clade with Ottowia beijingensis GCS-AN-3T, Ottowia thiooxydans DSM 14619T, Ottowia pentelensis RB3-7T and 'Ottowia shaoguanensis' J5-66T, showing the highest similarity to O. beijingensis GCS-AN-3T (96.3 %). The major fatty acids were C16 : 0, summed feature 3 (C16 : 1ω6c and/or C16 : 1ω7c) and summed feature 8 (C18 : 1ω6c and/or C18 : 1ω7c). The predominant respiratory quinone was Q-8. The polar lipids present were diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylmonomethylethanolamine, two unidentified aminolipids and two unidentified lipids. The genomic DNA G+C content was 66.80 mol%. These results supported that strain KADR8-3T was clearly distinguishable from its closely related species and represents a novel species of the genus Ottowia, for which the name Ottowia oryzae is proposed. The type strain is KADR8-3T (=KACC 19325T=NBRC 113109T).

Polyphasic characterization of four soil-derived phenanthrene-degrading Acidovorax strains and proposal of Acidovorax carolinensis sp. nov.

Four bacterial strains identified as members of the Acidovorax genus were isolated from two geographically distinct but similarly contaminated soils in North Carolina, USA, characterized, and their genomes sequenced. Their 16S rRNA genes were highly similar to those previously recovered during stable-isotope probing (SIP) of one of the soils with the polycyclic aromatic hydrocarbon (PAH) phenanthrene. Heterotrophic growth of all strains occurred with a number of organic acids, as well as phenanthrene, but no other tested PAHs. Optimal growth occurred aerobically under mesophilic temperature, neutral pH, and low salinity conditions. Predominant fatty acids were C16:1ω7c/C16:1ω6c, C16:0, and C18:1ω7c, and were consistent with the genus. Genomic G+C contents ranged from 63.6 to 64.2%. A combination of whole genome comparisons and physiological analyses indicated that these four strains likely represent a single species within the Acidovorax genus. Chromosomal genes for phenanthrene degradation to phthalate were nearly identical to highly conserved regions in phenanthrene-degrading Delftia, Burkholderia, Alcaligenes, and Massilia species in regions flanked by transposable or extrachromosomal elements. The lower degradation pathway for phenanthrene metabolism was inferred by comparisons to described genes and proteins. The novel species Acidovorax carolinensis sp. nov. is proposed, comprising the four strains described in this study with strain NA3T as the type strain (=LMG 30136, =DSM 105008).

Acidovorax kalamii sp. nov., isolated from a water sample of the river Ganges.

A Gram-stain-negative, rod-shaped, aerobic, straw yellow, motile strain, designated KNDSW-TSA6T, belonging to the genus Acidovorax, was isolated from a water sample of the river Ganges, downstream of the city of Kanpur, Uttar Pradesh, India. Cells were aerobic, non-endospore-forming and motile with single polar flagella. It differed from its phylogenetically related strains by phenotypic characteristics such as hydrolysis of urea, gelatin, casein and DNA, and the catalase reaction. The major fatty acids were C16 : 1ω7c/C16 : 1ω6c, C16 : 0 and C18 : 1ω7c/C18 : 1ω6c. Phylogenetic analysis based on 16S rRNA and housekeeping genes (gyrb, recA and rpoB gene sequences), confirmed its placement within the genus Acidovorax as a novel species. Strain KNDSW-TSA6T showed highest 16S rRNA sequence similarity to Acidovorax soli BL21T (98.9 %), Acidovorax delafieldii ATCC 17505T (98.8 %), Acidovorax temperans CCUG 11779T (98.2 %), Acidovorax caeni R-24608T (97.9 %) and Acidovorax radicis N35T (97.6 %). The digital DNA-DNA hybridization and average nucleotide identity values calculated from whole genome sequences between strain KNDSW-TSA6T and the two most closely related strains A. soli BL21T and A. delafieldii ATCC 17505T were below the threshold values of 70 and 95 % respectively. Thus, the data from the polyphasic taxonomic analysis clearly indicates that strain KNDSW-TSA6T represents a novel species, for which the name Acidovorax kalamii sp. nov. is proposed. The type strain is Acidovorax kalamii (=MTCC 12652T=KCTC 52819T=VTCC-B-910010T).

Polaromonas ginsengisoli sp. nov., isolated from ginseng field soil.

A Gram-reaction-negative, strictly aerobic, milky-white and rod-shaped bacterium (designated Gsoil 115T) isolated from ginseng field soil was characterized by a polyphasic approach to clarify its taxonomic position. Strain Gsoil 115T grew optimally at 30 °C and at pH 7.0 on Reasoner's 2A agar medium. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain Gsoil 115T belongs to the genus Polaromonas and was most closely related to Polaromonaseurypsychrophila B717-2T (98.6 %), Polaromonasvacuolata 34-PT (98.3 %), Polaromonasjejuensis NBRC 106434T (98.1 %), Polaromonas aquatic CCUG 39402T (97.7 %) and Polaromonascryoconiti Cr4-35T (97.5 %). The DNA G+C content was 60.9 mol%. The DNA-DNA hybridization relatedness between strain Gsoil 115T and P. eurypsychrophila B717-2T, P. vacuolata 34-PT, P. jejuensis NBRC 106434T, P. aquatic CCUG 39402T and P. cryoconiti Cr4-35T were 31.2, 21.6, 16.9, 8.7 and 10.1 %, respectively. The major polar lipids were phosphatidylglycerol (PG), diphosphatidylglycerol (DPG) and phosphatidylethanolamine (PE). The sole respiratory quinone was Q-8. The major fatty acids were C16 : 0 and summed feature 3 (C16 : 1ω7c and/or C16 : 1ω6c), which supported the affiliation of strain Gsoil 115T to the genus Polaromonas. Moreover, the physiological, biochemical and low level of DNA-DNA relatedness value allowed the phenotypic and genotypic differentiation of strain Gsoil 115T from the recognized species of the genus Polaromonas. Therefore, strain Gsoil 115T represents a novel species of the genus Polaromonas, for which the name Polaromonas ginsengisoli sp. nov. is proposed, with the type strain Gsoil 115T (LMG 23393T=KCTC 12577T).

Ramlibacter alkalitolerans sp. nov., alkali-tolerant bacterium isolated from soil of ginseng.

A novel bacterial strain, designated CJ661T, was isolated from soil of ginseng in Anseong, South Korea. Cells of strain CJ661T were white-coloured, Gram-staining-negative, non-motile, aerobic and rod-shaped. Strain CJ661T grew optimally at 30 °C and pH 7.0. The analysis of 16S rRNA gene sequence of strain CJ661T showed that it belongs to the genus Ramlibacter within the family Comamonadaceae and was most closely related to Ramlibacter ginsenosidimutans KCTC 22276T (98.1 %), followed by Ramlibacter henchirensis DSM 14656T (97.1 %). DNA-DNA relatedness levels of strain CJ661T were 40.6 % to R. ginsenosidimutans KCTC 22276T and 25.0 % to R. henchirensis DSM 14656T. The major isoprenoid quinone was ubiquinone (Q-8). The predominant polar lipids were phosphatidylethanolamine, diphosphatidylglycerol and phosphatidylglycerol. The major cellular fatty acids of strain CJ661T were summed feature 3 (C16 : 1 ω6c and/or C16 : 1 ω7c), C16 : 0 and summed feature 8 (C18 : 1 ω7c and/or C18 : 1 ω6c). The G+C content of the genomic DNA was 65.4 mol%. On the basis polyphasic taxonomic data, strain CJ661T represents a novel species in the genus Ramlibacter, for which name Ramlibacter alkalitolerans sp. nov. is proposed; the type strain is CJ661T (=KACC 19305T=JCM 32081T).

Hydrogenophaga aquatica sp. nov., isolated from a hot spring.

A polyphasic approach was used to characterize an aerobic, Gram-negative, rod-shaped bacterium (designated strain CC-KL-3T) isolated from a hot spring. Phylogenetic analyses based on 16S rRNA genes indicated that strain CC-KL-3T showed highest sequence similarity to Hydrogenophaga bisanensis (97.7 %) and Hydrogenophaga atypica (97.6 %) and lower sequence similarity to other species (less than 97.6 %). The levels of DNA-DNA relatedness between strain CC-KL-3T, H. bisanensis and H. atypica were estimated to be 13.0 and 8.7 % (the reciprocal value was 14.7 and 6.3 %). Strain CC-KL-3T was non-motile, without apparent flagella and able to grow between 15-42 °C (optimal 30 °Ð¡), pH 6.0-8.0 (optimal 7.0) and 0-2 % (w/v) NaCl (optimal 0 %). The DNA G+C content was 61.4 mol% and the major quinone system was ubiquinone (Q-8). The polyamine profile revealed the predominance of 2-hydroxyputrescine and putrescine and the dominant cellular fatty acids were C16 : 0 (28.9 %), C16 : 1ω7c/C16 : 1ω6c (41.4 %) and C18 : 1ω7c/C18 : 1ω6c (11.9 %). These data corroborated the affiliation of strain CC-KL-3T to the genus Hydrogenophaga. Based on the distinct phylogenetic, phenotypic and chemotaxonomic traits, and the results of comparative 16S rRNA gene sequence analysis, strain CC-KL-3T is considered to represent a novel species of the genus Hydrogenophaga, affiliated to the family Comamonadaceae, for which the name Hydrogenophaga aquatica sp. nov. is proposed. The type strain is CC-KL-3T (=BCRC 80937T=JCM 31216T).

Hydrogenophaga crassostreae sp. nov., isolated from a Pacific oyster.

A Gram-negative, motile, rod-shaped, and aerobic bacterial strain, designated LPB0072T, was isolated from a Pacific oyster (Crassostrea gigas). Autotrophic growth with hydrogen gas was not observed. Cells oxidized thiosulfate to sulfate and reduced nitrate to nitrite. The complete genome sequence of strain LPB0072T (CP017476) is 4.94 Mb in length and contains 4459 protein-coding genes, with a G+C content of 61.3 mol%. Analysis of the 16S rRNA gene sequence indicated that strain LPB0072T belongs to the genus Hydrogenophaga, with greatest sequence similarity to the type strain of Hydrogenophaga taeniospiralis (97.5 %). The isoprenoid quinone (Q-8) and the major cellular fatty acids (C16 : 1ω7c and/or C16 : 1ω6c, C16 : 0 and C17 : 1ω6c) identified were concordant with the chemotaxonomic properties of the genus Hydrogenophaga. The average nucleotide identities with closely related species were below the suggested boundary for species delineation, indicating that the isolate is a novel species. Numerous physiological and biochemical features also distinguished the isolate from other known Hydrogenophaga species. Based on the polyphasic data presented in this study, strain LPB0072T should be classified as a novel species in the genus Hydrogenophaga, and the name Hydrogenophaga crassostreae sp. nov. is proposed. The type strain is LPB0072T (=KACC 18705T=JCM 31188T).

Rhodoferax koreense sp. nov, an obligately aerobic bacterium within the family Comamonadaceae, and emended description of the genus Rhodoferax.

Gram-staining-negative, uniflagellated, rod-shaped, designated as DCY110T, was isolated from sludge located in Gangwon province, Republic of Korea. The phylogenetic tree of 16S rRNA gene sequence showed that the strain DCY110T belonged to the genus Rhodoferax with a close similarity to Rhodoferax saidenbachensis DSM 22694T (97.7%), Rhodoferax antarcticus DSM 24876T (97.5%), Rhodoferax ferrireducens DSM 15236T (97.3%), and Rhodoferax fermentans JCM 7819T (96.7%). The predominant isoprenoid quinine was ubiquinone (Q-8). DNA G + C content was 62.8 mol%. The major polar lipids were phosphatidylethanolamine and two unidentified phospholipids. The major fatty acids (> 10%) were C12:0, C16:0, summed feature 3 (which comprised C16:1 ω7c and/or C16:1 ω6c). The DNA-DNA relatedness values between the strain DCY110T and the closely related relatives used in this study were lower than 70%. Based on the following polyphasic analysis, the strain DCY110T is considered as a novel species of the genus Rhodoferax, for which the name Rhodoferax koreense sp. nov. is proposed. The type strain is DCY-110T (= KCTC 52288T = JCM 31441T).

Ramlibacter monticola sp. nov., isolated from forest soil.

During a study of bacterial diversity in forest soil, strain G-3-2T, a Gram-stain-negative, light brown-coloured, non-motile, rod- or coccoid-shaped bacterium, was isolated. It was able to grow at 15-37 °C, at pH 5.5-10.0 and at 0-0.5 % (w/v) NaCl concentration. The strain was taxonomically characterized by a polyphasic approach. Based on the 16S rRNA gene sequence analysis, strain G-3-2T belongs to the genus Ramlibacter and is closely related to Ramlibacter ginsenosidimutans BXN5-27T (98.69 % sequence similarity), Ramlibacter henchirensis TMB834T (96.98 %), Ramlibacter tataouinensis TTB310T (96.49 %) and Ramlibacter solisilvae 5-10T (96.42 %). The only respiratory quinone was ubiquinone-8. The major polar lipids were phosphatidylethanolamine, phosphatidylglycerol and diphosphatidylglycerol. The predominant fatty acids of strain G-3-2T were C16 : 0, summed feature 3 (C16 : 1ω7c and/or C16 : 1ω6c), C17 : 0 cyclo, summed feature 8 (C18 : 1ω7c and/or C18 : 1ω6c) and C10 : 0 3-OH. The genomic DNA G+C content of this novel strain was 68.9 mol%. The DNA-DNA relatedness between strain G-3-2T and R. ginsenosidimutans BXN5-27T was 44.7 %, which falls below the threshold value of 70 % for the strain to be considered as novel. The morphological, physiological, chemotaxonomic and phylogenetic analyses clearly distinguished this strain from its closest phylogenetic neighbours. Thus, strain G-3-2T represents a novel species of the genus Ramlibacter, for which the name Ramlibacter monticola sp. nov. is proposed. The type strain is G-3-2T (=KEMB 9005-573T=KACC 19175T=JCM 31918T).

Bifunctional quorum-quenching and antibiotic-acylase MacQ forms a 170-kDa capsule-shaped molecule containing spacer polypeptides.

Understanding the molecular mechanisms of bacterial antibiotic resistance will help prepare against further emergence of multi-drug resistant strains. MacQ is an enzyme responsible for the multi-drug resistance of Acidovorax sp. strain MR-S7. MacQ has acylase activity against both N-acylhomoserine lactones (AHLs), a class of signalling compounds involved in quorum sensing, and ß-lactam antibiotics. Thus, MacQ is crucial as a quencher of quorum sensing as well as in conferring antibiotic resistance in Acidovorax. Here, we report the X-ray structures of MacQ in ligand-free and reaction product complexes. MacQ forms a 170-kDa capsule-shaped molecule via face-to-face interaction with two heterodimers consisting of an α-chain and a ß-chain, generated by the self-cleaving activity of a precursor polypeptide. The electron density of the spacer polypeptide in the hollow of the molecule revealed the close orientation of the peptide-bond atoms of Val20SP-Gly21SP to the active-site, implying a role of the residues in substrate binding. In mutational analyses, uncleaved MacQ retained degradation activity against both AHLs and penicillin G. These results provide novel insights into the mechanism of self-cleaving maturation and enzymatic function of N-terminal nucleophile hydrolases.