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Applied and Environmental Microbiology, October 2009, p. 6110-6123, Vol. 75, No. 19
0099-2240/09/$08.00+0     doi:10.1128/AEM.00914-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Transcriptomic Response of Escherichia coli O157:H7 to Oxidative Stress{triangledown} ,{dagger}

Siyun Wang,1 Kaiping Deng,2 Sam Zaremba,3 Xiangyu Deng,1 Chiahui Lin,1 Qian Wang,1 Mary Lou Tortorello,2 and Wei Zhang1*

National Center for Food Safety and Technology, Illinois Institute of Technology, Chicago, Illinois,1 U.S. Food and Drug Administration, Summit Argo, Illinois 60501,2 Enteropathogen Resource Integration Center, SRA International, Rockville, Maryland 208523

Received 22 April 2009/ Accepted 26 July 2009

Chlorinated water is commonly used in industrial operations to wash and sanitize fresh-cut, minimally processed produce. Here we compared 42 human outbreak strains that represented nine distinct Escherichia coli O157:H7 genetic lineages (or clades) for their relative resistance to chlorine treatment. A quantitative measurement of resistance was made by comparing the extension of the lag phase during growth of each strain under exposure to sublethal concentrations of sodium hypochlorite in Luria-Bertani or brain heart infusion broth. Strains in clade 8 showed significantly (P < 0.05) higher resistance to chlorine than strains from other clades of E. coli O157:H7. To further explore how E. coli O157:H7 responds to oxidative stress at transcriptional levels, we analyzed the global gene expression profiles of two strains, TW14359 (clade 8; associated with the 2006 spinach outbreak) and Sakai (clade 1; associated with the 1996 radish sprout outbreak), under sodium hypochlorite or hydrogen peroxide treatment. We found over 380 genes were differentially expressed (more than twofold; P < 0.05) after exposure to low levels of chlorine or hydrogen peroxide. Significantly upregulated genes included several regulatory genes responsive to oxidative stress, genes encoding putative oxidoreductases, and genes associated with cysteine biosynthesis, iron-sulfur cluster assembly, and antibiotic resistance. Identification of E. coli O157:H7 strains with enhanced resistance to chlorine decontamination and analysis of their transcriptomic response to oxidative stress may improve our basic understanding of the survival strategy of this human enteric pathogen on fresh produce during minimal processing.

* Corresponding author. Mailing address: National Center for Food Safety and Technology, Illinois Institute of Technology, Summit Argo, IL 60501. Phone: (708) 563-2980. Fax: (708) 563-1873. E-mail: zhangw{at}iit.edu

{triangledown} Published ahead of print on 7 August 2009.

{dagger} Supplemental material for this article may be found at http://aem.asm.org/.

Applied and Environmental Microbiology, October 2009, p. 6110-6123, Vol. 75, No. 19
0099-2240/09/$08.00+0     doi:10.1128/AEM.00914-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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