Project description:Integrating laterally acquired virulence genes into the backbone regulatory network is important for the pathogenesis of Escherichia coli O157:H7, which has captured many virulence genes through horizontal transfer during evolution. GadE is an essential transcriptional activator of glutamate decarboxylase (GAD) system, the most efficient acid resistance mechanism in E. coli. The full contribution of GadE to the acid resistance and virulence of pathogenic E. coli O157:H7 remains largely unknown. We inactivated gadE in E. coli O157:H7 Sakai and compared global transcription profiles with that of wild type in exponential and stationary phases of growth using microarrays containing 6088 ORFs from three E. coli genomes. gadE inactivation significantly altered the expression of 60 genes independent of growth phase and 122 genes in a growth phase-dependent manner. Inactivation of gadE markedly down-regulated the expression of gadA, gadB, gadC and many acid fitness island genes in a growth phase-dependent manner. Nineteen genes encoded on the locus of enterocyte effacement (LEE), including ler, showed a significant increase in expression upon gadE inactivation. Altogether, our data indicate that GadE is critical for acid resistance of E. coli O157:H7 and plays an important role in virulence by down-regulating expression of LEE.
Project description:Deletion of yedL was found to signifcantly decrease type three secretion in EHEC O157:H7. Transcriptional profiles of Escherichia coli O157: H7 and the isogenic yedL mutant were generated and compared.
Project description:Deletion of yhaO was found to signifcantly decrease type three secretion in EHEC O157:H7. Transcriptional profiles of Escherichia coli O157: H7 and the isogenic yhaO mutant were generated and compared.
Project description:Pathogenic biofilms have been associated with persistent infections due to their high resistance to antimicrobial agents. To identify non-toxic biofilm inhibitors for enterohemorrhagic Escherichia coli O157:H7, indole-3-acetaldehyde was used and reduced E. coli O157:H7 biofilm formation. Global transcriptome analyses revealed that indole-3-acetaldehyde most repressed two curli operons, csgBAC and csgDEFG, and induced tryptophanase (tnaAB) in E. coli O157:H7 biofilm cells. Electron microscopy showed that indole-3-acetaldehyde reduced curli production in E. coli O157:H7. Together, this study shows that Actinomycetales are an important resource of biofilm inhibitors as well as antibiotics.
Project description:Cinnamaldehyde is a natural antimicrobial and has been found to be effective against many foodborne pathogens including Escherichia coli O157:H7. Although its antimicrobial effects have been well investigated, limited information is available on its effects at the molecular level. Sublethal treatment at 200 mg/l cinnamaldehyde inhibited growth of E. coli O157:H7 at 37oC and for ≤ 2 h caused cell elongation, but from 2 to 4 h growth resumed and cells reverted to normal length. To understand this transient behaviour, genome-wide transcriptional analysis of E. coli O157:H7 was performed at 2 and 4 h exposure to cinnamaldehyde. Drastically different gene expression profiles were obtained at 2 and 4 h. At 2 h exposure, cinnamaldehyde induced overexpression of many oxidative stress-related genes, reduced DNA replication, and synthesis of protein, O-antigen and fimbriae. At 4 h, many cinnamaldehyde-induced repressive effects on E. coli O157:H7 gene expressions were reversed and oxidatve stress genes were nolonger differentially expressed.
Project description:Transcript abundance in Escherichia coli O157:H7 was determined in the presence or absence of pulsed expression of the small RNA, AsxR.
Project description:The transcriptome of Escherichia coli K-12 has been widely studied over a variety of conditions for the past decade while such studies involving E. coli O157:H7, its pathogenic cousin, are just now being conducted. To better understand the impact of an anaerobic environment on E. coli O157:H7, global transcript levels of strain EDL933 cells grown aerobically were compared to cells grown anaerobically using microarrays.
Project description:The transcriptome of Escherichia coli K-12 has been widely studied over a variety of conditions for the past decade while such studies involving E. coli O157:H7, its pathogenic cousin, are just now being conducted. To better understand the impact of intracellular life within a ruminant and environmental protozoan on E. coli O157:H7, global transcript levels of strain EDL933 cells inside Acanthamoeba were compared to cell grown in the protozoan media (ATCC PYG712) by microarray.
Project description:Escherichia coli O157:H7 strains have been classified into different genotypes based on the presence of specific shiga toxin-encoding bacteriophage insertion sites. Genotypes that are predominant in clinical isolates are named clinical genotypes and those that are isolated mostly from bovine sources are bovine-biased genotypes. To determine whether inherent differences in gene expression could possibly explain the variation in infectivity of these genotypes, we compared the expression patterns of O157:H7 strains isolated from cattle, which belonged to either clinical genotype 1 or bovine-biased genotype 5. Important virulence factors of O157, including locus of enterocyte effacement, enterohemolysin, and pO157 plasmid encoded genes, showed increased expression in clinical genotype. Genes essential for acid resistance such as gadA, gadB, and gadC and other stress fitness-associated genes were up-regulated in the bovine-biased genotype 5. Overall, these results suggest that clinical genotype 1 strains more commonly cause human illness because of an enhanced ability to express O157 virulence factors known to be important for disease pathogenesis. By contrast, strains of the bovine-biased genotype 5 appear to be more resistant to adverse environmental conditions, which enable them to survive well in bovines without causing disease.