RESUMO
Concatenated sequence analysis with 16S rRNA, rpoB and fusA genes identified a bacterial strain (IRBG74) isolated from root nodules of the aquatic legume Sesbania cannabina as a close relative of the plant pathogen Rhizobium radiobacter (syn. Agrobacterium tumefaciens). However, DNA:DNA hybridization with R. radiobacter, R. rubi, R. vitis and R. huautlense gave only 44%, 5%, 8% and 8% similarity respectively, suggesting that IRBG74 is potentially a new species. Additionally, it contained no vir genes and lacked tumour-forming ability, but harboured a sym-plasmid containing nifH and nodA genes similar to those in other Sesbania symbionts. Indeed, IRBG74 effectively nodulated S. cannabina and seven other Sesbania spp. that nodulate with Ensifer (Sinorhizobium)/Rhizobium strains with similar nodA genes to IRBG74, but not species that nodulate with Azorhizobium or Mesorhizobium. Light and electron microscopy revealed that IRBG74 infected Sesbania spp. via lateral root junctions under flooded conditions, but via root hairs under non-flooded conditions. Thus, IRBG74 is the first confirmed legume-nodulating symbiont from the Rhizobium (Agrobacterium) clade. Cross-inoculation studies with various Sesbania symbionts showed that S. cannabina could form fully effective symbioses with strains in the genera Rhizobium and Ensifer, only ineffective ones with Azorhizobium strains, and either partially effective (Mesorhizobium huakii) or ineffective (Mesorhizobium plurifarium) symbioses with Mesorhizobium. These data are discussed in terms of the molecular phylogeny of Sesbania and its symbionts.
Assuntos
Rhizobium/genética , Nódulos Radiculares de Plantas/microbiologia , Sesbania/microbiologia , Aciltransferases/análise , Aciltransferases/genética , Proteínas de Bactérias/análise , Proteínas de Bactérias/genética , DNA Bacteriano/análise , DNA Bacteriano/genética , Fixação de Nitrogênio , Oxirredutases/análise , Oxirredutases/genética , Fator G para Elongação de Peptídeos/análise , Fator G para Elongação de Peptídeos/genética , Filogenia , Plasmídeos/análise , Plasmídeos/genética , RNA Ribossômico 16S/análise , RNA Ribossômico 16S/genética , Rhizobium/ultraestrutura , Nódulos Radiculares de Plantas/ultraestrutura , Alinhamento de Sequência , Análise de Sequência de DNA , Sesbania/ultraestrutura , Especificidade da Espécie , SimbioseRESUMO
The taxonomic position of "Agrobacterium radiobacter strain 204," used in Russia as a cereal crop growth promoting inoculant, was derived by a polyphasic approach. The phenotypic analyses gave very similar biochemical profiles for strain 204, Rhizobium radiobacter NCIMB 9042 (formerly the A. radiobacter type strain) and R. radiobacter NCIMB 13307 (formerly the Agrobacterium tumefaciens type strain). High percentage similarities, above the species separation level, were observed between the 16S rRNA, fusA and rpoB housekeeping gene sequences of these three strains, and the genomic DNA-DNA hybridisation of strain 204 against the type strain of R. radiobacter NCIMB 9042 was over 70%. Strain 204 is not phytopathogenic and it does not fix atmospheric N2 or form a physical association with the roots of barley. Strain 204 culture and culture supernatant stimulated the rate of mobilisation of seed reserves of barley in darkness and promoted its shoot growth in the light. Gibberellic acid (GA) concentration was 1.3 microM but indole acetic acid was undetectable (< 50 nM) in cultures of strain 204. It is concluded that strain 204 is phenotypically and genotypically very similar to the current R. radiobacter type strain and that the mechanism of its effect on growth of cereals is via the production of plant growth promoting substances. GA is likely to play an important role in the strain 204 stimulation of early growth of barley.
Assuntos
Agrobacterium tumefaciens/classificação , Agrobacterium tumefaciens/fisiologia , Produtos Agrícolas/microbiologia , Agrobacterium tumefaciens/genética , Proteínas de Bactérias/genética , Técnicas de Tipagem Bacteriana , Produtos Agrícolas/crescimento & desenvolvimento , DNA Bacteriano/química , DNA Bacteriano/genética , DNA Ribossômico/química , DNA Ribossômico/genética , RNA Polimerases Dirigidas por DNA/genética , Genes de RNAr , Giberelinas/biossíntese , Hordeum/crescimento & desenvolvimento , Hordeum/microbiologia , Ácidos Indolacéticos/metabolismo , Dados de Sequência Molecular , Fixação de Nitrogênio/genética , Hibridização de Ácido Nucleico , Oxirredutases/genética , Fator G para Elongação de Peptídeos/genética , Filogenia , Doenças das Plantas/microbiologia , Brotos de Planta/crescimento & desenvolvimento , Reação em Cadeia da Polimerase , RNA Ribossômico 16S/genética , Federação Russa , Análise de Sequência de DNA , Homologia de Sequência do Ácido Nucleico , Solanum tuberosum/microbiologiaRESUMO
'Pseudomonas fluorescens subsp. cellulosa' NCIMB 10462 has been demonstrated by a polyphasic taxonomic approach to be a member of the genus Cellvibrio. 16S rDNA sequence analysis suggests that this is the only genus that could accept this specimen. The sequence is 95.5% similar to that of Cellvibrio mixtus subsp. mixtus ACM 2601T (the type strain of the type species of the genus), which is its closest relation. The genomic DNA G + C content was determined to be 53.3 mol%, which is similar to the values obtained for the validly described Cellvibrio species. DNA-DNA hybridization experiments have shown that strain NCIMB 10462T (= NCDO 2697T) represents a novel species; therefore, it is proposed that it be designated as the type strain of the novel species Cellvibrio japonicus sp. nov. This study also used 16S rDNA analysis, DNA-DNA hybridization experiments and phenotypic testing to revive the species Cellvibrio vulgaris sp. nov., nom. rev. and Cellvibrio fulvus sp. nov., nom. rev. C. vulgaris NCIMB 8633T (=LMG 2848T) and C. fulvus NCIMB 8634T (=LMG 2847T) are the proposed type strains.
Assuntos
Cellvibrio/classificação , Pseudomonas fluorescens/classificação , RNA Ribossômico 16S/análise , Composição de Bases , Cellvibrio/genética , Cellvibrio/metabolismo , DNA Bacteriano/análise , DNA Bacteriano/genética , Dados de Sequência Molecular , Hibridização de Ácido Nucleico , Filogenia , Pseudomonas fluorescens/genética , Pseudomonas fluorescens/isolamento & purificação , RNA Ribossômico 16S/genética , Análise de Sequência de DNA , Microbiologia do SoloRESUMO
The microbial degradation of xylan is a key biological process. Hardwood 4-O-methyl-D-glucuronoxylans are extensively decorated with 4-O-methyl-D-glucuronic acid, which is cleaved from the polysaccharides by alpha-glucuronidases. In this report we describe the primary structures of the alpha-glucuronidase from Cellvibrio mixtus (C. mixtus GlcA67A) and the alpha-glucuronidase from Pseudomonas cellulosa (P. cellulosa GlcA67A) and characterize P. cellulosa GlcA67A. The primary structures of C. mixtus GlcA67A and P. cellulosa GlcA67A, which are 76% identical, exhibit similarities with alpha-glucuronidases in glycoside hydrolase family 67. The membrane-associated pseudomonad alpha-glucuronidase released 4-O-methyl-D-glucuronic acid from 4-O-methyl-D-glucuronoxylooligosaccharides but not from 4-O-methyl-D-glucuronoxylan. We propose that the role of the glucuronidase, in combination with cell-associated xylanases, is to hydrolyze decorated xylooligosaccharides, generated by extracellular hemicellulases, to xylose and 4-O-methyl-D-glucuronic acid, enabling the pseudomonad to preferentially utilize the sugars derived from these polymers.