Dataset Information

Transcriptome analysis of rectal tissues of E. coli O157 super-shedding and E. coli O157 negative cattle

ABSTRACT: Total RNA from rectal tissues of E. coli O157 super-shedders and non-shedders were sequenced using Illumina Hiseq 2000 system. For comparative analysis, differentially expressed genes were identified with edgeR. Fifteen of differentially expressed genes were related to innate and adaptive immune functions and were down-regulated in super-shedders, which could be one of reasons for super-shedding phenomenon.

ORGANISM(S): Bos taurus

PROVIDER: GSE67099 | GEO | 2016/03/20

SECONDARY ACCESSION(S): PRJNA278944

REPOSITORIES: GEO

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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.

Dataset Information

Transcriptome analysis of rectal tissues of E. coli O157 super-shedding and E. coli O157 negative cattle

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