RESUMO
Acinetobacter pittii 978-A_19 was obtained from a parrot with pneumonia. It is resistant to ampicillin, carbenicillin, cephalosporins, clindamycin, and trimethoprim + sulfamethoxazole. The genome encodes a new blaADC allele, a blaOXA-502 gene, possesses several virulence genes related to adherence and biofilm formation, and has types I, II, and IV secretion systems.
RESUMO
Fifty rhizobial isolates from root nodules of Mimosa affinis, a small leguminous plant native to Mexico, were identified as Rhizobium etli on the basis of the results of PCR-RFLP and RFLP analyses of small-subunit rRNA genes, multilocus enzyme electrophoresis and DNA-DNA homology. They are, however, a restricted group of lineages with low genetic diversity within the species. The isolates from M. affinis differed-from the R. etli strains that orginated from bean plants (Phaseolus vulgaris) in the size and replicator region of the symbiotic plasmid and in symbiotic-plasmid-borne traits such as nifH gene sequence and organization, melanin production and host specificity. A new biovar, bv. mimosae, is proposed within R. etli to encompass Rhizobium isolates obtained from M. affinis. The strains from common bean plants have been designated previously as R. etli bv. phaseoli. Strains of both R. etli biovars could nodulate P. vulgaris, but only those of bv. mimosae could form nitrogen-fixing nodules on Leucaena leucocephala.
Assuntos
Fabaceae/microbiologia , Oxirredutases , Plantas Medicinais , Rhizobium/classificação , Rhizobium/genética , Conjugação Genética , Impressões Digitais de DNA , DNA Bacteriano/genética , Eletroforese/métodos , Enzimas/análise , Genes de RNAr , Variação Genética , Dados de Sequência Molecular , Nitrogenase/genética , Raízes de Plantas/microbiologia , Plasmídeos/genética , Reação em Cadeia da Polimerase , Polimorfismo de Fragmento de Restrição , Rhizobium/isolamento & purificação , SimbioseRESUMO
Azorhizobium caulinodans is able to fix nitrogen in the free-living state and in symbiosis with the tropical legume Sesbania rostrata. The bacteria accumulate poly-beta-hydroxybutyrate (PHB) under both conditions. The structural gene for PHB synthase, phbC, was inactivated by insertion of an interposon. The mutant strains obtained were devoid of PHB, impaired in their growth properties, totally devoid of nitrogenase activity ex planta (Nif-), and affected in nucleotide pools and induced Fix- nodules devoid of bacteria. The Nif- phenotype was the consequence of the lack of nifA transcription. Nitrogenase activity was partially restored to a phbC mutant by constitutive expression of the nifA gene. However, this constitutive nifA expression had no effect on the nucleotide content or on growth of the phbC mutant. It is suggested that PHB is required for maintaining the reducing power of the cell and therefore the bacterial growth. These observations also suggest a new control of nifA expression to adapt nitrogen fixation to the availability of carbon and reducing equivalents.
Assuntos
Aciltransferases/genética , Proteínas de Bactérias/genética , Regulação Bacteriana da Expressão Gênica/fisiologia , Hidroxibutiratos/metabolismo , Poliésteres/metabolismo , Rhizobiaceae/genética , Fatores de Transcrição/genética , Aciltransferases/fisiologia , Fabaceae/microbiologia , Genes Bacterianos/genética , Dados de Sequência Molecular , Mutagênese Insercional , Fixação de Nitrogênio/genética , Nitrogenase/metabolismo , Nucleotídeos/análise , Raízes de Plantas , Plantas Medicinais , Rhizobiaceae/enzimologia , Rhizobiaceae/crescimento & desenvolvimentoRESUMO
Pyruvate carboxylase (PYC) is a biotin-dependent enzyme catalyzing the anaplerotic conversion of pyruvate to oxaloacetate in Rhizobium etli strain CE3. A pyc::Tn5 mutant had severely reduced growth, or failed to grow on sugars, three-carbon organic acids or glycerol, consistent with these substrates being metabolized via pyruvate. Transconjugants expressing a pyc::beta-glucuronidase gene fusion had slightly increased apparent pyc transcription during growth on pyruvate as compared to succinate, similar to the modest carbon source dependent changes in PYC activity reported previously. Biotin supplementation of cultures growing on pyruvate dramatically increased PYC activity but not apparent pyc transcription. Bacteroids isolated from bean nodules did not contain detectable PYC activity while apparent pyc transcription occurred at a moderate level.
Assuntos
Proteínas de Bactérias/biossíntese , Regulação Bacteriana da Expressão Gênica , Regulação Enzimológica da Expressão Gênica , Piruvato Carboxilase/biossíntese , Rhizobium/enzimologia , Proteínas de Bactérias/genética , Biotina/farmacologia , Metabolismo dos Carboidratos , Indução Enzimática/efeitos dos fármacos , Fabaceae/microbiologia , Regulação Bacteriana da Expressão Gênica/efeitos dos fármacos , Regulação Enzimológica da Expressão Gênica/efeitos dos fármacos , Glicerol/metabolismo , Plantas Medicinais , Piruvato Carboxilase/genética , Ácido Pirúvico/metabolismo , Rhizobium/crescimento & desenvolvimento , Transcrição Gênica/efeitos dos fármacosRESUMO
The complete coding sequence of the nitrogenase reductase gene (nifH) is present in three different regions of a Rhizobium phaseoli symbiotic plasmid. Homology between two of the regions containing nifH coding sequences extends over 5 kilobases. These in turn share 1.3 kilobases of homology with the third region. The nucleotide sequences of the three nitrogenase reductase genes were found to be identical. Site-directed insertion mutagenesis indicated that none of the three genes is indispensable for nitrogen fixation during symbiosis with Phaseolus vulgaris. This implies that at least two of the reiterated genes can be functionally expressed.