Effect of γ-irradiation on gene expression of heat shock proteins in the foodborne pathogen Escherichia coli O157:H7

Abstract

Purpose: The expression levels of seven genes (clpB, dnaK, groES, grpE, htpG, htpX and ibpB) encoding heat shock proteins (HSP) in Escherichia coli O157:H7 (E. coli) gamma irradiated was investigated. Timing impact of post-irradiated RNA extraction on the expression levels of these seven genes was also studied at a dose damaging the bacterial cells (0.4 kGy).

Methods: Bacterial samples were γ-irradiated at 0.4 kGy and at a lethal dose of 1.3 kGy. RNA was extracted at 0 min post irradiation for both irradiation doses and at 15, 30, 60, 90 or 120 min post-irradiation at the dose damaging the cells. Quantification of the gene expression was performed using quantitative real-time polymerase chain reaction (q-RT-PCR).

Results: The expression of genes encoding HSP was a very dynamic process evolving rapidly when E. coli cells were irradiated at 0.4 kGy. Notably, groES, grpE and ibpB were more up- regulated at 1.3 kGy than those at 0.4 kGy.

Conclusions: For the seven genes studied there were more damaged proteins during irradiation at the lethal dose and this dose causes increased expression in HSP which contributes to damage reparation. Expression patterns of genes encoding HSP in E. coli treated by γ-irradiation are different from those treated by heat shock.

Keywords::

• Gene expression
• heat shock proteins
• E. coli
• irradiation
• qRT-PCR

Acknowledgements

The authors are grateful to Nordion International Inc. for the irradiation operations and thank.

Marie-Christine Groleau and Dominique J. Favreau for the many advices and suggestions.

Declaration of interest

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.

The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

This research was supported by the National Sciences and Engineering Research Council of Canada, Discovery Program. 155141-2009 K.T. is a Fellowship recipient of the Fondation Armand- Frappier.