E.coli O157 and E.coli O121 spiked in wheat flour
Ontology highlight
ABSTRACT:
PROVIDER: PRJNA430401 | ENA |
REPOSITORIES: ENA
Dataset's files
| Action | DRS | |||
|---|---|---|---|---|
| SRR6486880_1.fastq.gz | Fastqsanger.gz | |||
| SRR6486880_2.fastq.gz | Fastqsanger.gz | |||
| SRR6486890_1.fastq.gz | Fastqsanger.gz | |||
| SRR6486890_2.fastq.gz | Fastqsanger.gz | |||
| SRR6486881_1.fastq.gz | Fastqsanger.gz |
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Project description:Escherichia coli O157 presents a number of specific problems in terms of food safety and public health. It has been found that E. coli O157 is more resistant to a number of the stresses encountered during food production such as heat, pH and osmotic shock. This greater resistance is thought to contribute to the low infectious dose of E. coli O157 (<100 organisms). Moreover, E. coli O157 is associated with debilitating conditions such as haemorrhagic colitis and haemoytic uraemic syndrome, particularly in children and the elderly. We have been studying the stress responses of E. coli O157:H7 (Sakai) and comparing with a commensal strain of E. coli K-12, MG1655. We found that E. coli O157 (Sakai) is more sensitive to oxidative stress than MG1655. A microarray study of these strains treated with sub-lethal concentrations (0.5mg/ml) of menadione revealed big differences in their responses. In E. coli O157 (Sakai), 540 genes responded significantly to the treatment compared to 121 genes in MG1655. One surprising finding from the microarray data was the observation that many iron-transport genes were up-regulated in E. coli O157 (Sakai) whereas relatively few were induced in MG1655 despite the fact that the bacteria were grown in a medium containing ample iron. We speculated that the induction of iron transport genes in an iron-rich medium might have contributed to the enhanced killing of E. coli O157 (Sakai) through triggering of a Fenton reaction. We speculated that the difference in sensitivity to oxidative stress might be due to differences in the intracellular iron content of E. coli O157 and MG1655. We found that E. coli O157 contains ~50% more iron than MG1655 and believe that during oxidative stress, this iron is released by damaged proteins. The greater levels of free iron in E. coli O157 will trigger a greater Fenton reaction that can damage the ferric uptake regulator (Fur), resulting in unregulated iron transport. In MG1655, the lower iron content results in a smaller Fenton reaction, enabling the cellular protection systems to limit damage and protect Fur.
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Project description:Background: Enterohemorrhagic Escherichia coli (EHEC) O157 causes severe food-bone illness in humans. The chromosome of O157 consists of 4.1-Mb backbone sequences shared by benign E. coli K-12, and 1.4-Mb O157-specific sequences encoding many virulence determinants such as Shiga toxin genes (stxs) and the locus of enterocyte effacement (LEE). Non-O157 EHECs belonging to clonal lineages distinct from O157 also cause similar illness in humans. According to the parallel evolution model, they have independently acquired the major virulence determinants, stxs and LEE. However, the genomic differences between O157 and non-O157 EHECs have not yet systematically been analyzed. Results: By using the microarray and Whole Genome PCR scanning analyses, we performed a whole genome comparison of 20 EHEC strains of O26, O111, and O103 serotypes with O157. In non-O157 EHEC strains, although genome sizes were similar with or rather larger than O157 and the backbone regions were well conserved, O157-specific regions were very poorly conserved. Only around 20% of the O157-specific genes were fully conserved in each non-O157 serotype. However, the non-O157 EHECs contained a significant number of virulence genes found on prophages and plasmids in O157, and also multiple prophages similar but significantly divergent from those in O157. Conclusion: Although O157 and non-O157 EHECs have independently acquired a huge amount of serotype- or strain-specific genes by lateral gene transfer, they share an unexpectedly large number of virulence genes. Independent infections of similar but distinct bacteriophages carrying these virulence determinants appear to be involved in the parallel evolution of EHEC. Keywords: comparative genomic hybridization, CGH
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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.
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