RESUMO
Fimbrial adhesins that mediate attachment to host cells are produced by most virulent Escherichia coli isolates. These virulence factors play an important role in the initial stages of bacterial colonization and also in determination of the host and tissue specificity. Isolates belonging to serotype O78 are known to cause a large variety of clinical syndromes in farm animals and humans and have been shown to produce several types of adherence fimbriae. We studied the fimbrial adhesin from an avian septicemic E. coli isolate of serotype O78. Analysis of the genetic organization of the fac (fimbria of avian E. coli) gene cluster indicates that it belongs to the S-fimbrial adhesin family. Seven open reading frames coding for major and minor structural subunits were identified, and most of them showed a high degree of homology to the corresponding Sfa and Foc determinants. The least-conserved open reading frame was facS, encoding a protein known to play an important role in determining adherence specificity in other S-fimbrial gene clusters.
Assuntos
Adesinas de Escherichia coli/genética , Infecções por Escherichia coli/veterinária , Escherichia coli/genética , Genes Bacterianos , Doenças das Aves Domésticas/microbiologia , Adesinas de Escherichia coli/química , Sequência de Aminoácidos , Animais , Galinhas , Clonagem Molecular , Escherichia coli/química , Escherichia coli/metabolismo , Infecções por Escherichia coli/microbiologia , Fímbrias Bacterianas/genética , Dados de Sequência Molecular , Família Multigênica , Mapeamento por Restrição , Sepse/microbiologia , Sepse/veterinária , Análise de Sequência de DNARESUMO
Online sensitive monitoring of gene expression is essential for understanding microbial life and microbial communities, especially under stress-inducing conditions, such as the presence of environmental pollutants. We describe here a novel use of promoter-based electrochemical biosensing for online and in situ monitoring of gene expression in response to pollutants. As a model system, we used a cadmium-responsive promoter from Escherichia coil fused to a promoterless lacZ gene, which was monitored using an electrochemical assay of beta-galactosidase activity. This whole-cell biosensor could detect, within minutes, nanomolar concentrations of cadmium in water, sea water and soil samples, and it can be used for continuous online and in situ monitoring.
Assuntos
Técnicas Biossensoriais , Cádmio/análise , Monitoramento Ambiental , Poluentes Ambientais/análise , Escherichia coli , Adenosina Trifosfatases , Eletroquímica , Escherichia coli/genética , Escherichia coli/metabolismo , Genes Reporter/genética , Óperon Lac/genética , Regiões Promotoras Genéticas , Proteínas Recombinantes/biossíntese , Água do Mar/microbiologia , Microbiologia do Solo , beta-Galactosidase/biossínteseRESUMO
Using in vivo translational gene fusion in Escherichia coli K-12 we identified a gene that is specifically induced by heavy metals, cadmium, mercury and zinc, at nmolar concentrations. This gene was identified by homology to known zinc and cadmium transporters. We created a disruption of the gene that resulted only in a minor increase in sensitivity to cadmium, suggesting that the fusion, which is at the carboxy-terminal end of the molecule, probably allows for at least partial activity of the protein.
Assuntos
Adenosina Trifosfatases/genética , Escherichia coli/efeitos dos fármacos , Escherichia coli/genética , Regulação Bacteriana da Expressão Gênica , Metais Pesados/farmacologia , Fusão Gênica Artificial , Cádmio/metabolismo , Cádmio/farmacologia , Escherichia coli/crescimento & desenvolvimento , Genes Bacterianos , Resposta ao Choque Térmico/genética , Estresse Oxidativo/genética , Biossíntese de Proteínas , beta-Galactosidase/metabolismoRESUMO
Several septicemic Escherichia coli O78 strains, isolated from different sources, were characterized phenotypically and genotypically. Two avian isolates, one of which is known to carry the AC/I fimbriae, hybridized with the sfa determinant in colony dot-blot assay. Southern hybridizations with specific sfa probes, following pulsed-field gel electrophoresis (PFGE), showed positive hybridization to the same fragment in each of these strains. Determination of the N-terminal amino acid sequence of the AC/I major subunit gene revealed high similarity to the sequence of the SfaA-II protein. These data suggest that the adhesin gene cluster, coding for AC/I fimbriae, belongs to the S-fimbrial adhesin family.
