Class 1 In-Tn5393c array contributed to antibiotic resistance of non-pathogenic Pseudoxanthomonas mexicana isolated from a wastewater bioreactor treating streptomycin.

The emergence of antibiotic resistance in retort to environmental pollutants during wastewater treatment still remains elusive. Here, we first to investigate the emergence of antibiotic resistance in an environmental non-pathogenic bacterium, Pseudoxanthomonas mexicana isolated from a lab-scale bioreactor treating wastewater containing streptomycin. The molecular mechanism of antibiotic resistance development was evaluated in its genomic, transcriptional, and proteomic levels. The streptomycin resistant (SR) strain showed strong resistance to streptomycin (MIC > 600 µg/mL) as well to sulfamethoxazole, ampicillin, and kanamycin (≥250 µg/mL). A 13.4 kb class-1-integron array consisting of a new arrangement of gene cassette (IS6100-sul1-aadA2-catB3-aacA1-2-aadB-int1-IS256-int) linked with Tn5393c transposon was identified in the SR strain, which has only been reported in clinical pathogens so far. iTRAQ-LC-MS/MS proteomics revealed 22 up-regulated proteins in the SR strain growing under 100 mg L-1 streptomycin, involving antibiotic resistance, toxin production, stress response, and ribosomal protein synthesis. At the mRNA level, elevated expressions of ARGs (strA, strB, and aadB) and 30S-ribosomal protein genes (rpsA and rpsU) were observed in the SR strain. The results highlighted the genomic plasticity and multifaceted regulatory mechanism employed by P. mexicana in adaptation to high-level streptomycin during biological wastewater treatment.

Aerosticca soli gen. nov., sp. nov., an aerobic gammaproteobacterium isolated from crude oil-contaminated soil.

An aerobic bacterium, designated strain Dysh456T, was isolated from a crude oil-contaminated soil. Cells of strain Dysh456T were rod-shaped, motile, and Gram-stain-negative. Strain Dysh456T grew at 13-48 °C and pH 4.3-7.9. Major cellular fatty acids were iso-C15:0 (42.5%), iso-C17:0 (15.3%) and summed feature 9 (iso-C17:1 ω9c/C16:0 10-methyl [13.7%]). Major respiratory quinone was ubiquinone-8. The genome of strain Dysh456T consists of a single circular chromosome of 2,874,969 bp in length with G + C content of 68.3%. Phylogenetic analysis based on the 16S rRNA gene sequences indicated that strain Dysh456T belongs to the family Rhodanobacteraceae, but none of the existing genera can accommodate this novel isolate. On the basis of physiological, chemotaxonomic, and genomic properties, strain Dysh456T (= NBRC 112897T = DSM 105662T) is proposed as the type strain representing a novel species of novel genus, for which the name Aerosticca soli gen. nov., sp. nov. is proposed.

Rhodanobacter rhizosphaerae sp. nov., isolated from soil of ginseng rhizosphere.

A Gram-stain-negative, aerobic, non-motile, non-spore-forming, yellow and rod-shaped bacterium, designated strain CR164T, was isolated from the rhizosphere soil of a ginseng field at Geumsan in Korea. CR164T grew at between 15 and 37 °C (optimal growth at 28 °C), between pH 6.0 and 9.0 (optimal growth at pH 7.0) and at salinities of 0-1.0 % (w/v) NaCl, growing optimally in the absence of NaCl. The results of phylogenetic analyses based on 16S rRNA gene sequences indicated that CR164T represents a member of the genus Rhodanobacter, showing the highest sequence similarity to Rhodanobactercaeni MJ01T (98.5 %), Rhodanobacter ginsenosidimutans Gsoil 3054T (98.4 %), Rhodanobacter thiooxydans LCS2T (98.3 %), Rhodanobacter lindaniclasticus RP5557T (98.1 %), Rhodanobacter denitrificans 2APBS1T (98.0 %), Rhodanobacter fulvus Jip2T (97.6 %), Rhodanobacter soli DCY45T (97.3 %) and 'Rhodanobacterxiangquanii' BJQ-6 (97.0 %). The major fatty acids were iso-C17 : 1ω9c (21.8 %), iso-C15 : 0 (12.1 %), iso-C11 : 0 (11.9 %) and iso-C16 : 0 (11.1 %). The predominant ubiquinone was Q-8. The major polar lipids were diphosphatidylglycerol, phosphatidylethanolamine and phosphatidylglycerol. The G+C content of the genomic DNA was 62.3 mol%. DNA-DNA relatedness between CR164T and the type strains of eight other species of the genus ranged from 51 to 9 %. On the basis of the polyphasic analysis, CR164T represents a novel species of the genus Rhodanobacter, for which the name Rhodanobacter rhizosphaerae sp. nov. is proposed. The type strain is CR164T (=KACC 18699T=NBRC 111845T).

Luteimonas dalianensis sp. nov., an obligate marine bacterium isolated from seawater.

A marine bacterial strain, designated OB44-3(T), was isolated from a crude oil-contaminated seawater sample collected near Dalian Bay, China. Cells of strain OB44-3(T) were Gramnegative, aerobic, rod-shaped, and oxidase- and catalasepositive. The major fatty acids were branched-chain saturated iso-C15:0 (27.9%) and unsaturated iso-C17:1 ω9c (14.8%). The DNA G+C content was 64.6 mol%. Phylogenetic analysis based on the 16S rRNA gene sequence indicated that strain OB44-3(T) was a member of the genus Luteimonas (95-96% 16S rRNA gene sequence similarity); its closest neighbors were the type strains of Luteimonas terricola (96% sequence similarity), Luteimonas mephitis (96%), and Luteimonas lutimaris (96%). On the basis of phenotypic, chemotaxonomic, and phylogenetic distinctiveness, strain OB44-3(T) was considered to represent a novel species of the genus Luteimonas. The name Luteimonas dalianensis sp. nov. is proposed, with strain OB44-3(T) (=CGMCC 1.12191(T) =JCM 18136(T)) as the type strain.

Rhodanobacter umsongensis sp. nov., isolated from a Korean ginseng field.

A bacterial isolate designated GR24-2(T) was isolated from Korean soil used for cultivating ginseng (Panax ginseng C. A. Meyer). The strain was aerobic, Gram-negative, motile, and rod-shaped. It grew optimally at 28-30°C, pH 7.0, and in a range of 0-1% NaCl. Phylogenetically, the strain clustered with members of the genus Rhodanobacter. The strain exhibited the highest sequence similarities (>98%) with R. panaciterrae LnR5-47(T) (98.4%), R. soli DCY45(T) (98.2%), and R. ginsengisoli GR17-7(T) (98.0%). However, it also showed high sequence similarities (>97%) with some other Rhodanobacter and Dyella species. The strain contained Q-8 as the predominant respiratory quinone. The major fatty acids (greater than 10% of the total fatty acids) were iso-C17:1 ω9c (24.5%), iso-C16:0 (22.8%), anteiso-C15:0 (10.5%), and iso-C15:0 (10.1%). Its major polar lipids were phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, and an unknown aminophospholipid. The DNA G+C content of strain GR24-2(T) was 65.6 mol%. The strain showed less than 70% DNA relatedness values between the closely related Rhodanobacter and Dyella species. The phylogeny, phenotype, DNA-DNA hybridization, and chemotaxonomic data generated in this study reveal that the isolate is a novel species of the genus Rhodanobacter. The name proposed for this strain is Rhodanobacter umsongensis sp. nov. (type strain GR24-2(T) =KACC 12917(T) =DSM 21300(T)).

Aerobic uranium immobilization by Rhodanobacter A2-61 through formation of intracellular uranium-phosphate complexes.

Severe environmental problems arise from old uranium mines, which continue to discharge uranium (U) via acid mine drainage water, resulting in soil, subsoil and groundwater contamination. Bioremediation of U contaminated environments has been attempted, but most of the conceptual models propose U removal by cell suspensions of anaerobic bacteria. In this study, strain Rhodanobacter A2-61, isolated from Urgeiriça Mine, Portugal, was shown to resist up to 2 mM of U(vi). The conditions used (low nutrient content and pH 5) potentiated the interaction of the toxic uranyl ion with the tested strain. The strain was able to remove approximately 120 µM of U(vi) when grown aerobically in the presence of 500 µM U. Under these conditions, this strain was also able to lower the phosphate concentration in the medium and increased its capacity to take up inorganic phosphate, accumulating up to 0.52 µmol phosphate per optical density unit of the medium at 600 nm, after 24 hours, corresponding approximately to the late log phase of the bacterial culture. Microscopically dense intracellular structures with nanometer size were visible. The extent of U inside the cells was quantified by LS counting. EDS analysis of heated cells showed the presence of complexes composed of phosphate and uranium, suggesting the simultaneous precipitation of U and phosphate within the cells. XRD analysis of the cells containing the U-phosphate complexes suggested the presence of a meta-autunite-like mineral structure. SEM identified, in pyrolyzed cells, crystalline nanoparticles with shape in the tetragonal system characteristic of the meta-autunite-like mineral structures. U removal has been reported previously but mainly by cell suspensions and through release of phosphate. The innovative Rhodanobacter A2-61 can actively grow aerobically, in the presence of U, and can efficiently remove U(vi) from the environment, accumulating it in a structural form consistent with that of the mineral meta-autunite inside the cell, corresponding to effective metal immobilization. This work supports previous findings that U bioremediation could be achieved via the biomineralization of U(vi) in phosphate minerals.

Rhodanobacter denitrificans sp. nov., isolated from nitrate-rich zones of a contaminated aquifer.

Bacterial strains 2APBS1(T) and 116-2 were isolated from the subsurface of a nuclear legacy waste site where the sediments are co-contaminated with large amounts of acids, nitrate, metal radionuclides and other heavy metals. A combination of physiological and genetic assays indicated that these strains represent the first member of the genus Rhodanobacter shown to be capable of complete denitrification. Cells of strain 2APBS1(T) and 116-2 were Gram-negative, non-spore-forming rods, 3-5 µm long and 0.25-0.5 µm in diameter. The isolates were facultative anaerobes, and had temperature and pH optima for growth of 30 °C and pH 6.5; they were able to tolerate up to 2.0 % NaCl, although growth improved in its absence. Strains 2APBS1(T) and 116-2 contained fatty acid and quinone (ubiquinone-8; 100 %) profiles that are characteristic features of the genus Rhodanobacter. Although strains 2APBS1(T) and 116-2 shared high 16S rRNA gene sequence similarity with Rhodanobacter thiooxydans LCS2(T) (>99 %), levels of DNA-DNA relatedness between these strains were substantially below the 70 % threshold used to designate novel species. Thus, based on genotypic, phylogenetic, chemotaxonomic and physiological differences, strains 2APBS1(T) and 116-2 are considered to represent a single novel species of the genus Rhodanobacter, for which the name Rhodanobacter denitrificans sp. nov. is proposed. The type strain is 2APBS1(T) ( = DSM 23569(T) = JCM 17641(T)).

Rhodanobacter panaciterrae sp. nov., a bacterium with ginsenoside-converting activity isolated from soil of a ginseng field.

A novel gammaproteobacterium, designated LnR5-47(T), was isolated from soil of a ginseng field in Liaoning province, China. The isolate was a Gram-negative, aerobic, non-motile, non-spore-forming rod. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain LnR5-47(T) belonged to the genus Rhodanobacter. The isolate was most closely related to Rhodanobacter ginsengisoli GR17-7(T), Rhodanobacter terrae GP18-1(T), Dyella ginsengisoli Gsoil 3046(T), Rhodanobacter soli DCY45(T), Dyella soli JS12-10(T) and Dyella japonica IAM 15069(T) (98.0, 97.9, 97.7, 97.3, 97.2 and 97.1% 16S rRNA gene sequence similarity, respectively). Chemotaxonomic data (Q-8 as the predominant ubiquinone, and iso-C(16:0), iso-C(17:1)ω9c and iso-C(15:0) as the major fatty acids) also supported the affiliation of strain LnR5-47(T) with the genus Rhodanobacter. However, DNA-DNA relatedness between strain LnR5-47(T) and its closest phylogenetic neighbours was <25.8%. Moreover, physiological and biochemical tests phenotypically differentiated the isolate from other members of the genus Rhodanobacter. Therefore, strain LnR5-47(T) represents a novel species, for which the name Rhodanobacter panaciterrae sp. nov. is proposed; the type strain is LnR5-47(T) (=KACC 12826(T)=KCTC 22232(T)=LMG 24460(T)).

Panacagrimonas perspica gen. nov., sp. nov., a novel member of Gammaproteobacteria isolated from soil of a ginseng field.

A taxonomic study was carried out on Gsoil 142(T), a bacterial strain isolated from the soil collected in a ginseng field in Pocheon province, South Korea. Comparative 16S rRNA gene sequence studies showed a clear affiliation of this bacterium to the Gammaproteobacteria, and it was most closely related to Hydrocarboniphaga effusa ATCC BAA 332(T) (94.4%, 16S rRNA gene sequence similarity), Nevskia ramosa DSM 11499(T) (94.1%) and Alkanibacter difficilis MN154.3(T) (92.0%). Strain Gsoil 142(T) was a gram-negative, strictly aerobic, motile, and rod-shaped bacterium. The G+C content of the genomic DNA was 69.9% and predominant ubiquinone was Q-8. Major fatty acids were summed feature 8 (C(18:1) omega7c and/or omega6c, 36.3%), summed feature 3 (iso-C(15:0) 2-OH and/or C(16:1) omega7c, 20.6%) and C(16:0) (17.4%). The major polar lipids detected in strain Gsoil 142(T) were phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, and an unknown glycolipid. On the basis of polyphasic evidence, it is proposed that strain Gsoil 142(T) should be placed in a novel genus and species, for which the name Panacagrimonas perspica gen. nov., sp. nov. is proposed. The type strain is Gsoil 142(T) (= KCTC 12982(T) = LMG 23239(T)).

Rhodanobacter soli sp. nov., isolated from soil of a ginseng field.

Strain DCY45(T) was isolated from soil of a ginseng field in Pocheon Province, Korea. Strain DCY45(T) was Gram-negative, oxidase- and catalase-positive, motile and rod-shaped and produced yellow pigments on R2A agar. The organism grew optimally at 30 °C and at pH 7.0. The G+C content of the genomic DNA was 65.4 mol%. The predominant respiratory quinone was Q-8. The major fatty acids were iso-C(17 : 1)ω9c, iso-C(16 : 0) and iso-C(15 : 0). Phylogenetic analysis based on the 16S rRNA gene sequence was used to determine the taxonomic position of strain DCY45(T), which is most closely related to species of the genus Rhodanobacter, with similarity levels of 96.0-98.4 %; DNA-DNA relatedness with related strains was lower than 60 %. Strain DCY45(T) differed significantly from related type strains in phenotypic characteristics. On the basis of these phenotypic, genotypic and chemotaxonomic studies, strain DCY45(T) represents a novel species of the genus Rhodanobacter, for which the name Rhodanobacter soli sp. nov. is proposed. The type strain is DCY45(T) (=KCTC 22620(T) =JCM 16126(T)).

Dokdonella ginsengisoli sp. nov., isolated from soil from a ginseng field, and emended description of the genus Dokdonella.

A Gram-negative, aerobic, rod-shaped, non-motile, non-spore-forming bacterial strain, designated Gsoil 191T, was isolated from a soil sample from a ginseng field in Pocheon Province, South Korea, and was characterized taxonomically by using a polyphasic approach. Comparative 16S rRNA gene sequence analysis showed that strain Gsoil 191T belongs to the family Xanthomonadaceae and is related to Dokdonella fugitiva LMG 23001T (97.8% sequence similarity) and Dokdonella koreensis KCTC 12396T (96.9%). The G+C content of the genomic DNA was 68.7 mol%. The major respiratory quinone was Q-8 and the major fatty acids were iso-C17:1omega9c (30.6%), iso-C17:0 (21.6%) and iso-C15:0 (13.0%), supporting the affiliation of strain Gsoil 191T to the genus Dokdonella. DNA-DNA hybridization experiments showed that the DNA-DNA relatedness values between strain Gsoil 191T and its closest phylogenetic neighbours were below 40%. The results of physiological and biochemical tests allowed genotypic and phenotypic differentiation of strain Gsoil 191T from recognized species of the genus Dokdonella. On the basis of its phenotypic properties and phylogenetic distinctiveness, strain Gsoil 191T represents a novel species of the genus Dokdonella, for which the name Dokdonella ginsengisoli sp. nov. is proposed. The type strain is Gsoil 191T (=KCTC 12564T=DSM 17954T=CCUG 52462T).

Rhodanobacter ginsenosidimutans sp. nov., isolated from soil of a ginseng field in South Korea.

A novel gammaproteobacterium, designated Gsoil 3054(T), was isolated from soil of a ginseng field in Pocheon province, South Korea, and was characterized using a polyphasic approach to determine its taxonomic position. The strain was Gram-negative, aerobic, non-motile, non-spore-forming and rod-shaped. Phylogenetic analysis based on 16S rRNA gene sequences showed that the strain belonged to the genus Rhodanobacter; it was most closely related to Rhodanobacter fulvus Jip2(T) and Rhodanobacter thiooxydans LCS2(T) (97.9 and 97.2 % 16S rRNA gene sequence similarity, respectively). Chemotaxonomic data, i.e. Q-8 as the predominant ubiquinone and iso-C(15 : 0), 10-methyl C(16 : 0) and iso-C(17 : 0) as major fatty acids, also supported classification of strain Gsoil 3054(T) in the genus Rhodanobacter. However, DNA-DNA hybridization values of Gsoil 3054(T) with R. fulvus Jip2(T) and R. thiooxydans LCS2(T) were 45 and 31 %, respectively. Moreover, physiological and biochemical tests enabled strain Gsoil 3054(T) to be differentiated phenotypically from other established species of Rhodanobacter. Therefore, the isolate represents a novel species, for which the name Rhodanobacter ginsenosidimutans sp. nov. is proposed; the type strain is Gsoil 3054(T) (=KACC 12822(T) =DSM 21013(T) =KCTC 22231(T) =LMG 24457(T)).

Dyella ginsengisoli sp. nov., isolated from soil of a ginseng field in South Korea.

A Gram-negative, aerobic, yellow-pigmented, non-spore-forming, motile, rod-shaped bacterium, designated strain Gsoil 3046(T), was isolated from soil from a ginseng field in Pocheon Province, South Korea, and was characterized taxonomically by using a polyphasic approach. A comparative analysis of 16S rRNA gene sequences revealed that strain Gsoil 3046(T) belongs to the family Xanthomonadaceae in the Gammaproteobacteria. The greatest sequence similarity was found with respect to Dyella koreensis KCTC 12359(T) (97.7 %), Dyella japonica IAM 15069(T) (97.4 %), Frateuria aurantia DSM 6220(T) (96.7 %), Fulvimonas soli LMG 19981(T) (96.2 %) and Luteibacter rhizovicinus DSM 16549(T) (96.0 %). The phylogenetic distances from other recognized species within the family Xanthomonadaceae, including Dyella yeojuensis KACC 11405(T), were greater than 4.0 % (i.e. the sequence similarities were less than 96.0 %). DNA-DNA hybridization experiments showed that the levels of DNA-DNA relatedness between strain Gsoil 3046(T) and its phylogenetically closest neighbours were below 25 %. The G+C content of the genomic DNA was 66.6 mol%. In addition, the presence of ubiquinone Q-8 as the predominant respiratory quinone, iso-C(17 : 1)omega9c, iso-C(16 : 0), iso-C(15 : 0) and iso-C(17 : 0) as the major cellular fatty acids and iso-C(13 : 0) 3-OH and iso-C(11 : 0) 3-OH as the major hydroxy fatty acids supported the affiliation of strain Gsoil 3046(T) to the genus Dyella. On the basis of its phenotypic properties and phylogenetic distinctiveness, strain Gsoil 3046(T) represents a novel species in the genus Dyella, for which the name Dyella ginsengisoli sp. nov. is proposed. The type strain is Gsoil 3046(T) (=KCTC 12599(T)=DSM 18387(T)).

Nevskia soli sp. nov., isolated from soil cultivated with Korean ginseng.

A Gram-negative bacterium, designated strain GR15-1(T), was isolated from a field cultivated with Korean ginseng. Cells were strictly aerobic, motile with multipolar flagella and rod-shaped. The strain grew optimally at 25-28 degrees C and pH 6.0-7.0. The predominant fatty acids of strain GR15-1(T) were C(18 : 1)omega7c, C(16 : 0) and summed feature 2 (C(14 : 0) 3-OH and/or iso-C(16 : 1) I). The major isoprenoid quinone was ubiquinone 8. The G+C content of the genomic DNA was 63.9 mol%. Phylogenetic analysis showed that strain GR15-1(T) formed a phyletic cluster with Nevskia ramosa Soe1(T), with a 16S rRNA gene sequence similarity of 96.8 %. Based on phenotypic, chemotaxonomic and phylogenetic features, strain GR15-1(T) represents a novel species within the genus Nevskia, for which the name Nevskia soli sp. nov. is proposed. The type strain is GR15-1(T) (=KACC 11703(T) =DSM 19509(T)).

Arenimonas malthae sp. nov., a gammaproteobacterium isolated from an oil-contaminated site.

A Gram-negative, rod-shaped bacterium (CC-JY-1(T)) was isolated on nutrient agar from a soil sample collected from an oil-contaminated site located in Chyai county, Taiwan. 16S rRNA gene sequence analysis demonstrated that this isolate is unique, showing 96.7 % sequence similarity to the type strain of Arenimonas donghaensis and similarities of 93.0-93.8 % to species of the genera Thermomonas, Lysobacter and Silanimonas. The presence of ubiquinone Q-8, a polar lipid profile consisting of the major compounds diphosphatidylglycerol, phosphatidylglycerol and phosphatidylethanolamine and the fatty acid profile were in accordance with the phylogenetic affiliation of CC-JY-1(T). DNA-DNA reassociation experiments between CC-JY-1(T) and A. donghaensis KACC 11381(T) resulted in a mean relatedness value of 32 %, indicating that strain CC-JY1(T) represents a novel species in the genus Arenimonas, for which we propose the name Arenimonas malthae sp. nov. The type strain is CC-JY-1(T) (=CCUG 53596(T) =CIP 109310(T)).

Rhodanobacter ginsengisoli sp. nov. and Rhodanobacter terrae sp. nov., isolated from soil cultivated with Korean ginseng.

Two bacterial isolates from ginseng fields in Korea, strains GR17-7(T) and GP18-1(T), were characterized using a polyphasic approach. Phylogenetic analysis of their 16S rRNA gene sequences revealed a clear affiliation with the Gammaproteobacteria, and showed that the closest phylogenetic relationships were with members of the genus Rhodanobacter. The 16S rRNA gene sequence similarity between strains GR17-7(T) and GP18-1(T) was 97.2 %. Both strains showed 16S rRNA gene sequence similarities of 95.2-96.9 % to type strains of recognized Rhodanobacter species. The G+C contents of the DNA of strains GR17-7(T) and GP18-1(T) were 61.0 and 62.5 mol%, respectively. According to the DNA-DNA hydridization tests, the hybridization value between strains GR17-7(T) and GP18-1(T) was 34 %. Strains GR17-7(T) and GP18-1(T) showed less than 32 % DNA-DNA relatedness with Rhodanobacter fulvus KCTC 12098(T) and Rhodanobacter spathiphylli LMG 23181(T). Strains GR17-7(T) and GP18-1(T) were aerobic, Gram-negative, rod-shaped, and catalase- and oxidase-positive. Major fatty acids of both strains were iso-C(17 : 1)omega9c and iso-C(16 : 0). Based on the data presented, two novel Rhodanobacter species are proposed, with the names Rhodanobacter ginsengisoli sp. nov. (type strain GR17-7(T)=KACC 11762(T)=DSM 18993(T)) and Rhodanobacter terrae sp. nov. (type strain GP18-1(T)=KACC 11761(T)=DSM 19241(T)).

Pseudoxanthomonas spadix sp. nov., isolated from oil-contaminated soil.

A bacterial isolate from a sample of oil-contaminated soil was characterized using a polyphasic taxonomic approach. Comparative analysis of the 16S rRNA gene sequence showed that this isolate constituted a distinct phyletic line within the genus Pseudoxanthomonas, displaying >3.7 % sequence divergence with respect to recognised Pseudoxanthomonas species. The genus assignment was confirmed by a chemotaxonomic analysis, which revealed the presence of a fatty acid profile characteristic of members of the genus Pseudoxanthomonas (straight-chain saturated, unsaturated and branched-chain fatty acids of the iso/anteiso type and 3-hydroxylated fatty acids) and the presence of a ubiquinone with eight isoprene units (Q-8) as the predominant respiratory quinone. The novel isolate was distinguishable from other members of the genus Pseudoxanthomonas on the basis of a combination of phenotypic properties. The genotypic and phenotypic data show that the strain represents a novel species of the genus Pseudoxanthomonas, for which the name Pseudoxanthomonas spadix sp. nov. is proposed. The type strain is IMMIB AFH-5(T) (=DSM 18855(T)=CCUG 53828(T)).

Pseudoxanthomonas yeongjuensis sp. nov., isolated from soil cultivated with Korean ginseng.

A Gram-negative, strictly aerobic, non-spore-forming bacterium, motile by means of single polar flagellum and rod-shaped, designated strain GR12-1(T), was isolated from soil of a ginseng field in Yeongju region, Korea. Phylogenetic analysis based on 16S rRNA gene sequences indicated that this strain is related to members of the genus Pseudoxanthomonas, showing sequence similarity values ranged from 92.3 to 96.2 %. This organism grew at 5-33 degrees C, with optimum growth at 28 degrees C. Strain GR12-1(T) grew optimally in the presence of 0-2 % NaCl. The whole-cell fatty acid profile included iso-C(15 : 0), iso-C(17 : 1)omega9c, iso-C(16 : 0), iso-C(11 : 0) 3-OH and iso-C(17 : 0) as major components. The only isoprenoid quinone was ubiquinone 8 (Q-8). The DNA G+C content was 63.4 mol%. On the basis of phenotypic, genetic and phylogenetic data, strain GR12-1(T) should be classified as a member of a novel species of the genus Pseudoxanthomonas, for which the name Pseudoxanthomonas yeongjuensis sp. nov. is proposed, with strain GR12-1(T) (=KACC 11580(T)=DSM 18204(T)) as the type strain.

Suppression of damping-off disease in host plants by the rhizoplane bacterium Lysobacter sp. strain SB-K88 is linked to plant colonization and antibiosis against soilborne Peronosporomycetes.

We previously demonstrated that xanthobaccin A from the rhizoplane bacterium Lysobacter sp. strain SB-K88 suppresses damping-off disease caused by Pythium sp. in sugar beet. In this study we focused on modes of Lysobacter sp. strain SB-K88 root colonization and antibiosis of the bacterium against Aphanomyces cochlioides, a pathogen of damping-off disease. Scanning electron microscopic analysis of 2-week-old sugar beet seedlings from seeds previously inoculated with SB-K88 revealed dense colonization on the root surfaces and a characteristic perpendicular pattern of Lysobacter colonization possibly generated via development of polar, brush-like fimbriae. In colonized regions a semitransparent film apparently enveloping the root and microcolonies were observed on the root surface. This Lysobacter strain also efficiently colonized the roots of several plants, including spinach, tomato, Arabidopsis thaliana, and Amaranthus gangeticus. Plants grown from both sugar beet and spinach seeds that were previously treated with Lysobacter sp. strain SB-K88 displayed significant resistance to the damping-off disease triggered by A. cochlioides. Interestingly, zoospores of A. cochlioides became immotile within 1 min after exposure to a SB-K88 cell suspension, a cell-free supernatant of SB-K88, or pure xanthobaccin A (MIC, 0.01 microg/ml). In all cases, lysis followed within 30 min in the presence of the inhibiting factor(s). Our data indicate that Lysobacter sp. strain SB-K88 has a direct inhibitory effect on A. cochlioides, suppressing damping-off disease. Furthermore, this inhibitory effect of Lysobacter sp. strain SB-K88 is likely due to a combination of antibiosis and characteristic biofilm formation at the rhizoplane of the host plant.

Rhizosphere-induced selenium precipitation for possible applications in phytoremediation of se polluted effluents.

Two bacterial isolates were obtained in axenic culture from the rhizosphere soil of Astragalus bisulcatus, a legume able to hyperaccumulate selenium. Both strains resulted of particular interest for their high resistance to the toxic oxyanion SeO3(2-) (selenite, Se(IV)). On the basis of molecular and biochemical analyses, these two isolates were attributed to the species Bacillus mycoides and Stenotrophomonas maltophilia, respectively. Their capability in axenic culture to precipitate the soluble, bioavailable and highly toxic selenium form selenite to insoluble and relatively non-toxic Se(0) (elemental selenium) was evaluated in defined medium added with 0.2 or 0.5 mM Se(IV). Both strains showed to completely reduce 0.2 mM selenite in 120 h, while 0.5 mM Se(IV) was reduced up to 67% of the initial concentration by B. mycoides and to about 50% by S. maltophilia in 48 h. Together in a dual consortium, B. mycoides and S. maltophilia increased the kinetics of selenite reduction, thus improving the efficiency of the process. A model system for selenium rhizofiltration based on plant-rhizobacteria interactions has been proposed.