RESUMEN
Mutations in σE-regulated lipoproteins have previously been shown to impact bacterial viability under conditions of stress and during in vivo infection. YraP is conserved across a number of Gram-negative pathogens, including Neisseria meningitidis, where the homolog is a component of the Bexsero meningococcal group B vaccine. Investigations using laboratory-adapted Escherichia coli K-12 have shown that yraP mutants have elevated sensitivity to a range of compounds, including detergents and normally ineffective antibiotics. In this study, we investigate the role of the outer membrane lipoprotein YraP in the pathogenesis of Salmonella enterica serovar Typhimurium. We show that mutations in S Typhimurium yraP result in a defective outer membrane barrier with elevated sensitivity to a range of compounds. This defect is associated with attenuated virulence in an oral infection model and during the early stages of systemic infection. We show that this attenuation is not a result of defects in lipopolysaccharide and O-antigen synthesis, changes in outer membrane protein levels, or the ability to adhere to and invade eukaryotic cell lines in vitro.
Asunto(s)
Proteínas de la Membrana Bacteriana Externa/metabolismo , Lipoproteínas/metabolismo , Infecciones por Salmonella/microbiología , Infecciones por Salmonella/patología , Salmonella typhimurium/patogenicidad , Factores de Virulencia/metabolismo , Animales , Antibacterianos/farmacología , Proteínas de la Membrana Bacteriana Externa/genética , Línea Celular , Modelos Animales de Enfermedad , Células Epiteliales/microbiología , Humanos , Lipoproteínas/genética , Macrófagos/microbiología , Ratones Endogámicos C57BL , Pruebas de Sensibilidad Microbiana , Mutación , Salmonella typhimurium/efectos de los fármacos , Salmonella typhimurium/genética , Salmonella typhimurium/crecimiento & desarrollo , Virulencia , Factores de Virulencia/genéticaRESUMEN
Aeromonas caviae is a Gram-negative, motile and rod-shaped facultative anaerobe that is increasingly being recognized as a cause of diarrhea in children. Here we present the first genome sequence of an A. caviae strain that was isolated as the sole pathogen from a child with profuse diarrhea.
Asunto(s)
Aeromonas caviae/genética , Genoma Bacteriano , Niño , Enfermedades Transmisibles Emergentes/microbiología , Gastroenteritis/microbiología , Infecciones por Bacterias Gramnegativas/microbiología , Humanos , Datos de Secuencia MolecularRESUMEN
Although Neisseria gonorrhoeae is a prolific source of eight c-type cytochromes, little is known about how its electron transfer pathways to oxygen are organized. In this study, the roles in the respiratory chain to oxygen of cytochromes c(2), c(4), and c(5), encoded by the genes cccA, cycA, and cycB, respectively, have been investigated. Single mutations in genes for either cytochrome c(4) or c(5) resulted in an increased sensitivity to growth inhibition by excess oxygen and small decreases in the respiratory capacity of the parent, which were complemented by the chromosomal integration of an ectopic, isopropyl-beta-d-thiogalactopyranoside (IPTG)-inducible copy of the cycA or cycB gene. In contrast, a cccA mutant reduced oxygen slightly more rapidly than the parent, suggesting that cccA is expressed but cytochrome c(2) is not involved in electron transfer to cytochrome oxidase. The deletion of cccA increased the sensitivity of the cycB mutant to excess oxygen but decreased the sensitivity of the cycA mutant. Despite many attempts, a double mutant defective in both cytochromes c(4) and c(5) could not be isolated. However, a strain with the ectopically encoded, IPTG-inducible cycB gene with deletions in both cycA and cycB was constructed: the growth and survival of this strain were dependent upon the addition of IPTG, so gonococcal survival is dependent upon the synthesis of either cytochrome c(4) or c(5). These results define the gonococcal electron transfer chain to oxygen in which cytochromes c(4) and c(5), but not cytochrome c(2), provide alternative pathways for electron transfer from the cytochrome bc(1) complex to the terminal oxidase cytochrome cbb(3).
Asunto(s)
Proteínas Bacterianas/metabolismo , Grupo Citocromo c/metabolismo , Citocromos c2/metabolismo , Transporte de Electrón/fisiología , Neisseria gonorrhoeae/metabolismo , Proteínas Bacterianas/genética , Western Blotting , Grupo Citocromo c/genética , Citocromos c2/genética , Transporte de Electrón/efectos de los fármacos , Transporte de Electrón/genética , Electroforesis en Gel de Poliacrilamida , Regulación Bacteriana de la Expresión Génica/efectos de los fármacos , Regulación Bacteriana de la Expresión Génica/genética , Humanos , Isopropil Tiogalactósido/farmacología , Mutación , Neisseria gonorrhoeae/efectos de los fármacos , Neisseria gonorrhoeae/genética , Oxígeno/farmacologíaRESUMEN
The Escherichia coli NarL protein is a global gene regulatory factor that activates transcription at many target promoters in response to nitrate and nitrite ions. Although most NarL-dependent promoters are also co-dependent on a second transcription factor, FNR protein, two targets, the yeaR and ogt promoters, are activated by NarL alone with no involvement of FNR. Biochemical and genetic studies presented here show that activation of the yeaR promoter is dependent on the binding of NarL to a single target centred at position -43.5, whereas activation at the ogt promoter requires NarL binding to tandem DNA targets centred at position -45.5 and -78.5. NarL-dependent activation at both the yeaR and ogt promoters is decreased in rich medium and this depends on Fis, a nucleoid-associated protein. DNase I footprinting studies identified Fis-binding sites that overlap the yeaR promoter NarL site at position -43.5, and the ogt promoter NarL site at position -78.5, and suggest that Fis represses both promoters by displacing NarL. The ogt gene encodes an O6-alkylguanine DNA alkyltransferase and, hence, this is the first report of expression of a DNA repair function being controlled by nitrate ions.