Isolation and Characterization of an Acidic, Salt-Tolerant Endoglucanase Cel5A from a Bacterial Strain Martelella endophytica YC6887 Genome.

A Martelella endophytica (M. endophytica) strain YC6887 was previously isolated from the roots of a halophyte, Rosa rugosa, which was sequenced and characterized. The genomic and proteomic analysis showed a carbohydrate-degrading enzyme, endoglucanase Cel5A which was further characterized. The protein analysis revealed that this endoglucanase belongs to glycosidic hydrolase family 5 (GH5) with catalytic domain. This gene encodes 349-residue polypeptide and shows closest similarity with cellulases of other Martelella species. The protein was purified to homogeneity and shown that it was a 39 kDa protein. The purified recombinant Cel5A endoglucanase exhibited maximum activity at 50 °C and pH 4.5. The enzyme was salt tolerant and retained more than 50% residual activity up to 15% NaCl. The homology model structure of Cel5A displayed that it is stable and compact protein structure consisting of eleven α-helical structures and eight ß-sheets. According to the predicted ligand binding site after superimposition with Pseudomonas stutzeri endoglucanase Cel5A (PDB ID: 4LX4), it consisted of five amino acid Asn157, Tyr116, Glu158, Glu270 and Trp303 that may be the expected active site of Cel5A from YC6887. This presented that our strain M. endophytica YC6887 that produces cellulase partially degrade the insoluble polysaccharides into reducing sugars.

Plant-Growth Promoting Bacillus oryzicola YC7007 Modulates Stress-Response Gene Expression and Provides Protection From Salt Stress.

High salt stress caused by ionic and osmotic stressors eventually results in the suppression of plant growth and a reduction in crop productivity. In our previous reports, we isolated the endophytic bacterium Bacillus oryzicola YC7007 from the rhizosphere of rice (Oryza sativa L.), which promoted plant growth and development and suppressed bacterial disease in rice by inducing systemic resistance and antibiotic production. In this study, Arabidopsis thaliana seedlings under salt stress that were bacterized with YC7007 displayed an increase in the number of lateral roots and greater fresh weight relative to that of the control seedlings. The chlorophyll content of the bacterized seedlings was increased when compared with that of untreated seedlings. The accumulation of salt-induced malondialdehyde and Na+ in seedlings was inhibited by their co-cultivation with YC7007. The expression of stress-related genes in the shoots and roots of seedlings was induced by YC7007 inoculation under salt stress conditions. Interestingly, YC7007-mediated salt tolerance requires SOS1, a plasma membrane-localized Na+/H+ antiporter, given that plant growth in sos2-1 and sos3-1 mutants was promoted under salt-stress conditions, whereas that of sos1-1 mutants was not. In addition, inoculation with YC7007 in upland-crops, such as radish and cabbage, increased the number of lateral roots and the fresh weight of seedlings under salt-stress conditions. Our results suggest that B. oryzicola YC7007 enhanced plant tolerance to salt stress via the SOS1-dependent salt signaling pathway, resulting in the normal growth of salt-stressed plants.

Bacillus velezensis YC7010 Enhances Plant Defenses Against Brown Planthopper Through Transcriptomic and Metabolic Changes in Rice.

Brown planthopper (BPH; Nilaparvata lugens Stål) is one of the most serious insect pests, which reduce rice yield remarkably in many rice-growing areas. A few plant growth-promoting rhizobacteria induce systemic resistance against herbivorous insects. Here we show that root drenching of rice seedlings with an endophytic strain Bacillus velezensis YC7010 enhanced defenses against BPH. Based on high-throughput transcriptome analysis, systemic resistance against BPH was induced by B. velezensis YC7010 via salicylic acid (SA)- and jasmonic acid (JA)-dependent pathways. Increased leaf contents of secondary metabolites, tricin and C-glycosyl flavone and cell-wall contents of lignin and cellulose were the key defense mechanisms inducing resistance against BPH during the three-way interaction. This study shows for the first time that chemical changes and strengthening of physical barriers play important roles simultaneously in plant defense against BPH in rice by the endophytic bacteria. This defense was induced by lipopeptides including a novel bacillopeptin X.

Martelella suaedae sp. nov. and Martelella limonii sp. nov., isolated from the root of halophytes.

Two Gram-stain-negative, aerobic and endophytic bacterial strains, designated YC7033T and YC7034T, were isolated from the roots of halophytes (Suaeda maritime and Limonium tetragonum, respectively) inhabiting tidal flats of the Sacheon area, Korea. The phylogenetic analyses of 16S rRNA gene sequences showed that the two strains were closely related to Martelella endophytica YC6887T, Martelella mangrovi BM9-1T, Martelella radicis BM5-7T and Martelella mediterranea DSM 17316T at 97.6-99.1 % similarity. Sequence similarities with the type strains of another closely related genus, Rhizobium, were lower than 95.0 %. Both strains contained ubiquinone-10 (Q-10) as the major respiratory quinone system. The G+C contents of the genomic DNA of strains YC7033T and YC7034T were 52.8 and 62.2 mol%, respectively. The major fatty acids of both strain YC7033T and strain YC7034T were summed feature 8 (C18 : 1ω7c and/or C18 : 1ω6c) and C19 : 0 cyclo ω8c. On the basis of phylogenetic analysis, and biochemical and phenotypic characteristics, strains YC7033T and YC7034T represent two novel species of the genus Martelella, for which the names Martelella suaedae sp. nov. (type strain: YC7033T=KACC 17175T=NBRC 109440T) and Martelella limonii sp. nov. (type strain: YC7034T=KACC 17176T=NBRC 109441T) are proposed, respectively.

Biological Control of Rice Bakanae by an Endophytic Bacillus oryzicola YC7007.

In our previous study, we reported that a novel endophytic bacterium Bacillus oryzicola YC7007 has suppressed bacterial diseases of rice via induced systemic resistance and antibiotic production. This endophytic strain, B. oryzicola YC7007 was used as a biological control agent against bakanae disease of rice caused by Fusarium fujikuroi, and its mechanism of interaction with the pathogen and the rice was further elucidated. Root drenching with B. oryzicola YC7007 suspension reduced the disease severity of bakanae significantly when compared with the untreated controls. The treatments of B. oryzicola YC7007 suspension (2.0 × 10(7) cfu/ml) to the rice rhizosphere reduced bakanae severity by 46-78% in pots and nursery box tests containing autoclaved and non-autoclaved soils. Moreover, in the detached rice leaves bioassay, the development of necrotic lesion and mycelial expansion of F. fujikuroi were inhibited significantly by spraying the culture filtrate of B. oryzicola YC7007. Drenching of ethyl acetate extracts of the culture filtrate to the rhizosphere of rice seedlings also reduced the bakanae disease severity in the plant culture dish tests. With the root drenching of B. oryzicola YC7007 suspension, the accumulation of hydrogen peroxide was observed at an early stage of rice seedlings, and a hormonal defense was elicited with and without pathogen inoculation. Our results showed that the strain B. oryzicola YC7007 had a good biocontrol activity against the bakanae disease of rice by direct inhibition, and was also capable of inducing systemic resistance against the pathogen via primed induction of the jasmonic acid pathway.

Roseomonas oryzicola sp. nov., isolated from the rhizosphere of rice (Oryza sativa L.).

A Gram-stain-negative, coccobacilli-shaped bacterium, designated YC6724T, was isolated from the rhizosphere of rice in Jinju, Korea. The taxonomy of strain YC6724T was studied using a polyphasic approach. Strain YC6724T grew optimally at 30 °C and pH 7.0-8.0. Comparative 16S rRNA gene sequence analyses showed that the strain was most closely related to Roseomonas soli 5N26T (98.4 % 16S rRNA gene sequence similarity), Roseomonas lacus THG33T(97.3 %) and Roseomonas terrae DS-48T (97.3 %). Sequence similarities with other species of the genus Roseomonas with validly published names were lower than 94.0 %. Phylogenetic analysis based on the 16S rRNA gene sequence showed that strain YC6724T formed a distinct phyletic lineage within the genus Roseomonas. Strain YC6724T had DNA-DNA relatedness values of 16.6 %, 44.0 % and 33.2 % with R. soli KACC 16376T, R. terrae KACC 12677T and R. lacus KACC 11678T, respectively. The predominant fatty acids of strain YC6724T were C18 : 1ω7c and/or C18 : 1ω6c, C16 : 0 and C18 : 1 2-OH. The polar lipid profile contained phosphatidylethanolamine, phosphatidylcholine, phosphatidylglycerol,diphosphatidylglycerol, an unknown aminolipid and two unknown lipids. The G+C content of the genomic DNA was 70.5 mol% and the major quinone was Q-10. Strain YC6724T contained spermidine as the major polyamine. On the basis of phenotypic, chemotaxonomic and molecular data, it is clear that strain YC6724T represents a novel species of the genus Roseomonas, for which the name Roseomonas oryzicola sp. nov. is proposed. The type strain is YC6724T (=KCTC 22478T=NBRC 109439T).

Nitrospirillum irinus sp. nov., a diazotrophic bacterium isolated from the rhizosphere soil of Iris and emended description of the genus Nitrospirillum.

A polyphasic approach was used to characterize a novel nitrogen-fixing bacterial strain, designated YC6995(T), isolated from the rhizosphere soil of Iris ensata var. spontanea (Makino) Nakai inhabiting a wetland located at an altitude of 960 m on Jiri Mountain, Korea. Strain YC6995(T) cells were Gram-negative, and rod-shaped, with motility provided by a single polar flagellum. Optimal growth conditions were 30 °C and pH 7.0. The major fatty acids of strain YC6995(T) were C18:1 ω7c, C18:1 2-OH and C16:0 3-OH. The major respiratory quinone was ubiquinone-10 (Q-10). The polar lipids were phosphatidylethanolamine, phosphatidyldimethylethanolamine, phosphatidylcholine, phosphatidylglycerol and unidentified glycolipids. The genomic DNA G+C content was 64.1 mol%. Phylogenetic analysis based on 16S rRNA gene sequences showed strain YC6995(T) to form a phyletic lineage with Nitrospirillum amazonense DSM 2787(T) with a high sequence similarity (97.2 %), but it displayed low sequence similarity with other remotely related genera, including Azospirillum (<93 %), Rhodocista (93.1-93.4 %), and Skermanella (91.2-93.3 %) in the family Alphaproteobacteria. Based on the phenotypic, chemotaxonomic, and phylogenetic evidences, strain YC6995(T) represents a novel species within the genus Nitrospirillum, for which the name Nitrospirillum irinus sp. nov. is proposed. The type strain is YC6995(T) (= KACC 13777(T) = DSM 22198(T)). An emended description of the genus Nitrospirillum is also proposed.

Bacillus oryzicola sp. nov., an Endophytic Bacterium Isolated from the Roots of Rice with Antimicrobial, Plant Growth Promoting, and Systemic Resistance Inducing Activities in Rice.

Biological control of major rice diseases has been attempted in several rice-growing countries in Asia during the last few decades and its application using antagonistic bacteria has proved to be somewhat successful for controlling various fungal diseases in field trials. Two novel endophytic Bacillus species, designated strains YC7007 and YC7010(T), with anti-microbial, plant growth-promoting, and systemic resistance-inducing activities were isolated from the roots of rice in paddy fields at Jinju, Korea, and their multifunctional activities were analyzed. Strain YC7007 inhibited mycelial growth of major rice fungal pathogens strongly in vitro. Bacterial blight and panicle blight caused by Xanthomonas oryzae pv. oryzae (KACC 10208) and Burkholderia glumae (KACC 44022), respectively, were also suppressed effectively by drenching a bacterial suspension (10(7) cfu/ml) of strain YC7007 on the rhizosphere of rice. Additionally, strain YC7007 promoted the growth of rice seedlings with higher germination rates and more tillers than the untreated control. The taxonomic position of the strains was also investigated. Phylogenetic analyses based on 16S rRNA gene sequences indicated that both strains belong to the genus Bacillus, with high similarity to the closely related strains, Bacillus siamensis KACC 15859(T) (99.67%), Bacillus methylotrophicus KACC 13105(T) (99.65%), Bacillus amyloliquefaciens subsp. plantarum KACC 17177(T) (99.60%), and Bacillus tequilensis KACC 15944(T) (99.45%). The DNA-DNA relatedness value between strain YC7010(T) and the most closely related strain, B. siamensis KACC 15859(T) was 50.4±3.5%, but it was 91.5±11.0% between two strains YC7007 and YC7010(T), indicating the same species. The major fatty acids of two strains were anteiso-C15:0 and iso C15:0. Both strains contained MK-7 as a major respiratory quinone system. The G+C contents of the genomic DNA of two strains were 50.5 mol% and 51.2 mol%, respectively. Based on these polyphasic studies, the two strains YC7007 and YC7010(T) represent novel species of the genus Bacillus, for which the name Bacillus oryzicola sp. nov. is proposed. The type strain is YC7010(T) (= KACC 18228(T)). Taken together, our findings suggest that novel endophytic Bacillus strains can be used for the biological control of rice diseases.

Complete Genome Sequence of Martelella endophytica YC6887, Which Has Antifungal Activity Associated with a Halophyte.

Martelella endophytica YC6887, which produces antifungal compounds against fungal and oomycete pathogens, was isolated from the root of a halophyte, Rosa rugosa, collected at a tidal flat in South Korea. Its full-genome sequence shows that it is a circular DNA, without a plasmid, of about 4.8 Mb in size.

Gynuella sunshinyii gen. nov., sp. nov., an antifungal rhizobacterium isolated from a halophyte, Carex scabrifolia Steud.

An antifungal bacterial strain, designated YC6258(T), was isolated from the rhizosphere of a halophyte (Carex scabrifolia Steud.) growing in a tidal flat area of Namhae Island, Korea. Cells of the strain were Gram-stain-negative, facultatively anaerobic, moderately halophilic, rod-shaped and motile by a single polar flagellum. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain YC6258(T) formed a phyletic lineage distinct from members of the most closely related genera, Saccharospirillum and Reinekea, with less than 91.2 % sequence similarities. The major cellular fatty acids were C18 : 1ω7c, C16 : 0 and Summed feature 3 (C16 : 1ω7c/ C16 : 1ω6c). The quinone system of strain YC6258(T) consisted mainly of ubiquinone Q-8. The polar lipid profile exhibited phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol and unknown lipids. The DNA G+C content was 48.9 mol%. Based on the phylogenetic and phenotypic characteristics, strain YC6258(T) should be classified as a representative of a novel species in a novel genus for which the name Gynuella sunshinyii gen. nov., sp. nov. is proposed. The type strain is YC6258(T) (KCCM 43015(T) = NBRC 109345(T)).

Draft Genome Sequence of Kitasatospora cheerisanensis KCTC 2395, Which Produces Plecomacrolide against Phytopathogenic Fungi.

Kitasatospora cheerisanensis KCTC 2395, which produces antifungal metabolites with bafilomycin derivatives, including bafilomycin C1-amide, was isolated from a soil sample at Mt. Jiri, South Korea. Here, we report its draft genome sequence, which contains 8.04 Mb with 73.6% G+C content and 7,810 protein-coding genes.

Labrenzia suaedae sp. nov., a marine bacterium isolated from a halophyte, and emended description of the genus Labrenzia.

An endophytic, Gram-staining-negative bacterium was isolated from sterilized roots of a plant, Suaeda maritima, growing on tidal flats. Cells of the strain were motile by means of a single polar flagellum and colonies were pigmented light brown. Strain YC6927(T) was able to grow at 15-37 °C (optimum at 28-30 °C) and at pH 5.0-10.0 (optimum at pH 7.0-8.0). The strain was able to grow at NaCl concentrations of 0-9.0 % (w/v), with optimum growth at 0-5.0 % NaCl. Comparison of 16S rRNA gene sequences showed that the strain was a member of the genus Labrenzia, exhibiting the highest similarity to Labrenzia marina mano18(T) (97.6 % sequence similarity). Strain YC6927(T) produced light-brown carotenoid pigments. The major respiratory quinone was Q-10 and the DNA G+C content was 58.5 mol%. The DNA-DNA relatedness between strain YC6927(T) and closely related strains was between 8.2±1.8 and 20.3±1.5 %. Strain YC6927(T) contained summed feature 8 (C18 : 1ω7c and/or C18 : 1ω6c) and C14 : 0 3-OH as major fatty acids, confirming the affiliation of the strain with the genus Labrenzia. The polar lipids consisted of phosphatidylglycerol, diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine, phosphatidylmonomethylethanolamine, an unknown aminolipid, an unknown phospholipid and five unknown lipids. On the basis of phylogenetic analysis, physiological and biochemical characterization and DNA-DNA hybridization data, strain YC6927(T) should be assigned to a novel species of the genus Labrenzia, for which the name Labrenzia suaedae sp. nov. is proposed. The type strain is YC6927(T) ( = KACC 13772(T) = DSM 22153(T)). An emended description of the genus Labrenzia is also proposed.

Cloning and functional characterization of endo-ß-1,4-glucanase gene from metagenomic library of vermicompost.

In the vermicomposting of paper mill sludge, the activity of earthworms is very dependent on dietetic polysaccharides including cellulose as energy sources. Most of these polymers are degraded by the host microbiota and considered potentially important source for cellulolytic enzymes. In the present study, a metagenomic library was constructed from vermicompost (VC) prepared with paper mill sludge and dairy sludge (fresh sludge, FS) and functionally screened for cellulolytic activities. Eighteen cellulase expressing clones were isolated from about 89,000 fosmid clones libraries. A short fragment library was constructed from the most active positive clone (cMGL504) and one open reading frame (ORF) of 1,092 bp encoding an endo-ß-1,4-glucanase was indentified which showed 88% similarity with Cellvibrio mixtus cellulase A gene. The endo-ß-1,4-glucanase cmgl504 gene was overexpressed in Escherichia coli. The purified recombinant cmgl504 cellulase displayed activities at a broad range of temperature (25-55°C) and pH (5.5-8.5). The enzyme degraded carboxymethyl cellulose (CMC) with 15.4 U, while having low activity against avicel. No detectable activity was found for xylan and laminarin. The enzyme activity was stimulated by potassium chloride. The deduced protein and three-dimensional structure of metagenome-derived cellulase cmgl504 possessed all features, including general architecture, signature motifs, and N-terminal signal peptide, followed by the catalytic domain of cellulase belonging to glycosyl hydrolase family 5 (GHF5). The cellulases cloned in this work may play important roles in the degradation of celluloses in vermicomposting process and could be exploited for industrial application in future.

Engineering of family-5 glycoside hydrolase (Cel5A) from an uncultured bacterium for efficient hydrolysis of cellulosic substrates.

Cel5A, an endoglucanase, was derived from the metagenomic library of vermicompost. The deduced amino acid sequence of Cel5A shows high sequence homology with family-5 glycoside hydrolases, which contain a single catalytic domain but no distinct cellulose-binding domain. Random mutagenesis and cellulose-binding module (CBM) fusion approaches were successfully applied to obtain properties required for cellulose hydrolysis. After two rounds of error-prone PCR and screening of 3,000 mutants, amino acid substitutions were identified at various positions in thermotolerant mutants. The most heat-tolerant mutant, Cel5A_2R2, showed a 7-fold increase in thermostability. To enhance the affinity and hydrolytic activity of Cel5A on cellulose substrates, the family-6 CBM from Saccharophagus degradans was fused to the C-terminus of the Cel5A_2R2 mutant using overlap PCR. The Cel5A_2R2-CBM6 fusion protein showed 7-fold higher activity than the native Cel5A on Avicel and filter paper. Cellobiose was a major product obtained from the hydrolysis of cellulosic substrates by the fusion enzyme, which was identified by using thin layer chromatography analysis.

Amorphus suaedae sp. nov., isolated from the root of a tidal flat plant, Suaeda maritima.

A novel bacterial strain, YC6899(T), was isolated from the root of Suaedae maritima growing on a tidal flat of Namhae Island, Korea. Cells were Gram-reaction-negative, rod-shaped, non-motile, slightly halophilic and heterotrophic. Strain YC6899(T) grew optimally at a salinity of 2-4 %, at 25-37 °C and at pH 6.5-8.0. Phylogenetic analysis of 16S rRNA gene sequences demonstrated that strain YC6899(T) was closely related to Amorphus orientalis YIM D10(T) (96.1 % similarity) and Amorphus coralli RS.Sph.026(T) (95.9 %). The polar lipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, unknown aminolipids, an unknown aminophospholipid, an unknown aminoglycolipid, unknown glycolipids and unknown lipids. The major fatty acids of strain YC6899(T) were C19 : 0 cyclo ω8c and C18 : 1ω7c. The G+C content of the genomic DNA was 61.3 mol%. Strain YC6899(T) contained ubiquinone-10 (Q-10) as the major respiratory quinone system. On the basis of phenotypic, chemotaxonomic and phylogenetic data, strain YC6899(T) represents a novel species within the genus Amorphus, for which the name Amorphus suaedae sp. nov. is proposed. The type strain is YC6899(T) ( = KACC 14912(T) = NBRC 107845(T)).

Mucilaginibacter gynuensis sp. nov., isolated from rotten wood.

A Gram-staining-negative, rod-shaped, aerobic bacterial strain designated YC7003(T), was isolated from a piece of rotten wood collected at Jinju, Korea. The taxonomic position of the strain was investigated using a polyphasic approach. The strain was catalase- and oxidase-positive, grew at 4-35 °C (optimum, 30 °C) and at pH 5.0-10.0 (optimum, pH 6.5-7.0). The major cellular fatty acids were C(16:1)ω7c and/or iso-C(15:0) 2-OH (summed feature 3), iso-C(15:0) and C(16 : 1)ω5c and the major respiratory quinone was MK-7. The total genomic DNA G+C content was 49.0 mol%. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain YC7003(T) belonged to the genus Mucilaginibacter in the family Sphingobacteriaceae with 94.4-97.2% sequence similarities with type strains of species of the genus Mucilaginibacter. The most closely related species was Mucilaginibacter mallensis MP1X4(T) (97.2%). The DNA-DNA relatedness value between strain YC7003(T) and M. mallensis MP1X4(T) was 21.7 ± 3.3%. Based on these data, strain YC7003(T) represents a novel species of the genus Mucilaginibacter, for which the name Mucilaginibacter gynuensis sp. nov. is proposed. The type strain is YC7003(T) ( =KACC 15532(T) =JCM 17705(T)).

Martelella endophytica sp. nov., an antifungal bacterium associated with a halophyte.

A Gram-staining-negative, non-spore-forming endophytic bacterium, designated strain YC6887(T), was isolated from a root sample of a halophyte, Rosa rugosa, collected from a tidal flat area of Namhae Island, located at the southern end of Korea. Strain YC6887(T) was found to exhibit inhibitory activity against oomycete plant pathogens. The cells were non-motile and aerobic rods. The strain was able to grow at 4-40 °C (optimum 28-30 °C) and at pH 5.0-9.0 (optimum pH 7.0-8.5). Strain YC6887(T) was able to grow at NaCl concentrations of 0-9 % (w/v) with optimum growth at 4-5 % (w/v) NaCl, but NaCl is not essential for growth. Comparison of 16S rRNA gene sequences showed that the strain was a member of the genus Martelella, a member of order Rhizobiales, exhibiting highest similarity with Martelella mediterranea (98.6 %). The DNA-DNA relatedness between strain YC6887(T) and M. mediterranea MACL11(T) was 19.8 ± 6.8. Chemotaxonomically, strain YC6887(T) contained C19 : 0 cyclo ω8c (28.0 %) and C18 : 1ω7c (17.9 %) as predominant fatty acids, confirming the affiliation of strain YC6887(T) with the genus Martelella. The major respiratory quinone was Q-10 and the DNA G+C content was 62.1 mol%. On the basis of phylogenetic analysis, physiological and biochemical characterization and DNA-DNA hybridization data, strain YC6887(T) should be classified as representing a novel species of the genus Martelella, for which the name Martelella endophytica sp. nov. is proposed. The type strain is YC6887(T) ( = KCCM 43011(T) = NBRC 109149(T)).

Mucilaginibacter jinjuensis sp. nov., with xylan-degrading activity.

A gram-negative, rod-shaped, pale-orange-pigmented bacterial strain with xylan-degrading activity designated YC7004(T) was isolated from a rotten-wood sample collected at Jinju, Korea, and its taxonomic position was investigated by using a polyphasic approach. The strain grew optimally on R2A medium at 30 °C and at pH 6. The major isoprenoid quinone was MK7 and major fatty acids were summed feature 3, iso-C15 : 0, C16 : 0, iso-C17 : 0 3-OH, iso-C17 : 1ω9c and C16 : 1ω5c. The G+C content of the genomic DNA was 40.0 mol%. Phylogenetic analysis based on the 16S rRNA gene sequences showed that the strain belongs to the genus Mucilaginibacter in the family Sphingobacteriaceae. The most closely related species were Mucilaginibacter daejeonensis (95.5 %), Mucilaginibacter frigoritolerans (94.6 %) and Mucilaginibacter mallensis (94.0 %). Based on the phylogenetic and chemotaxonomic data analyses, strain YC7004(T) represents a novel species of the genus Mucilaginibacter with the proposed name of Mucilaginibacter jinjuensis sp. nov. The type strain is YC7004(T) ( = KACC 16571(T) = NBRC 108856(T)).

Enhancement of geraniol resistance of Escherichia coli by MarA overexpression.

Improvement of a microorganism's tolerance against organic solvents is required for a microbial factory producing terpenoid based biofuels. The bacterial genes, marA, imp, cls and cti have been found to increase organic solvent tolerance. Thus, the tolerance against the following terpenoids (isopentenol, geraniol, myrcene, and farnesol) was studied with overexpression of marA, imp, cls and cti genes in Escherichia coli. The marA overexpression significantly enhanced the tolerance of E. coli against geraniol, whereas there was no tolerance improvement against the terpenoids by overexpression of cls and cti genes. The imp overexpression even yielded sensitive phenotype to the tested solvents. The colony forming efficiency of the marA overexpressing E. coli was increased by 10(4)-fold in plate overlay of geraniol compared to that of wild type E. coli and a two-fold decrease of intracellular geraniol accumulation was also observed in liquid culture of geraniol. Single knock-out mutations of marA, or one of the following genes (acrA, acrB and tolC) encoding AcrAB-TolC efflux pump made E. coli hypersensitive to geraniol. The geraniol tolerance conferred by marA overexpression was attributed to the AcrAB-TolC efflux pump that is activated by MarA.