RESUMO
The acidophilic proteobacterium Acidithiobacillus ferrooxidans is involved in the industrial biorecovery of copper. It is found in acidic environments in biofilms and is important in the biogeochemical cycling of metals and nutrients. Its genome contains a cluster of four genes, glyQ, glysS, gph, and act, that are predicted to encode the alpha and beta subunits of glycine tRNA synthetase, a phosphatase, and an acyltransferase, respectively (GenBank accession no. DQ149607). act, cloned and expressed in Escherichia coli, produces acyl homoserine lactones (AHLs) principally of chain length C14 according to gas chromatography and mass spectrometry measurements. The AHLs have biological activity as shown by in vivo studies using the reporter strain Sinorhizobium meliloti Rm41 SinI-. Reverse transcription-PCR (RT-PCR) experiments indicate that the four genes are expressed as a single transcript, demonstrating that they constitute an operon. According to semiquantitative RT-PCR results, act is expressed more highly when A. ferrooxidans is grown in medium containing iron than when it is grown in medium containing sulfur. Since AHLs are important intercellular signaling molecules used by many bacteria to monitor their population density in quorum-sensing control of gene expression, this result suggests that A. ferrooxidans has two quorum-sensing systems, one based on Act, as described herein, and the other based on a Lux-like quorum-sensing system, reported previously. The latter system was shown to be upregulated in A. ferrooxidans grown in sulfur medium, suggesting that the two quorum-sensing systems respond to different environmental signals that may be related to their abilities to colonize and use different solid sulfur- and iron-containing minerals.
Assuntos
4-Butirolactona/análogos & derivados , Acidithiobacillus/enzimologia , Acidithiobacillus/genética , Redes e Vias Metabólicas/genética , 4-Butirolactona/biossíntese , Acidithiobacillus/metabolismo , Aciltransferases/genética , Proteínas de Bactérias/genética , Clonagem Molecular , DNA Bacteriano/genética , Escherichia coli/genética , Escherichia coli/metabolismo , Cromatografia Gasosa-Espectrometria de Massas , Regulação Bacteriana da Expressão Gênica , Genes Bacterianos , Glicina-tRNA Ligase/genética , Ferro/metabolismo , Dados de Sequência Molecular , Família Multigênica , Óperon , Monoéster Fosfórico Hidrolases/genética , RNA Bacteriano/análise , RNA Mensageiro/análise , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Análise de Sequência , Sinorhizobium meliloti/efeitos dos fármacos , Sinorhizobium meliloti/fisiologia , Enxofre/metabolismoRESUMO
The "maize white spot" foliar disease is a problem of increasing importance to Brazilian maize crops. A bacterium isolated from water-soaked lesions from infected maize leaves was pathogenic in biological assays in vivo. It was identified as a Gram-negative, nonsporulating, facultative anaerobic bacterium, belonging to the genus Pantoea. Chemical study of the extracts from bacterial cultivation media allowed the identification of (S)-(-)-N-butanoyl-homoserine lactone and trace amounts of N-hexanoyl-homoserine lactone, widely recognized quorum-sensing signaling substances employed in cell-to-cell communication systems. The absolute configuration of natural (S)-(-)-N-butanoyl-homoserine lactone was determined by gas chromatography-flame ionization detection with a chiral stationary phase and by comparison of circular dichroism spectroscopic data with enantiopure synthetic substances. Biological evaluations with reporter Agrobacterium tumefaciens NTL4(pZLR4) were carried out with synthetic and natural products and also with extracts from maize leaves contaminated with the isolated bacterium, as well as from healthy leaves.
Assuntos
4-Butirolactona/análogos & derivados , Pantoea/metabolismo , Doenças das Plantas/microbiologia , Folhas de Planta/química , Zea mays/microbiologia , 4-Butirolactona/biossíntese , 4-Butirolactona/química , 4-Butirolactona/isolamento & purificação , Cromatografia GasosaRESUMO
A new serogroup of Vibrio cholerae non-O1, O:139, has been implicated in recent epidemics. It was scanned with a factor A-specific fluoresceine-conjugated monoclonal antibody, searching for antigen determinants by laser flow cytometry. First, a group of gram-negative 4-amine-4, 6 dideoxy-D-mannose antigen-related microorganisms were tested to assess monoclonal antibody cross reactions. Later, a clear recognition of antigen determinants was found with this monoclonal antibody, on V. cholerae non-O1, O:136, Bengal, and MO45 strains, showing no cross reactions with the antigenically related non O1, O:22, and Inaba and Ogawa O1 strains. On the other hand, factor A of V. cholerae O1 strains was recognized by the specific monoclonal antibody and a discrete factor A on V. cholerae non-O1, O:139, Bengal and MO45 strains was detected.