HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: mic.0.031435-0v1 155/11/3589    most recent Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via CrossRef Google Scholar Articles by Uhlich, G. A. PubMed PubMed Citation Articles by Uhlich, G. A. Agricola Articles by Uhlich, G. A.

KatP contributes to OxyR-regulated hydrogen peroxide resistance in Escherichia coli serotype O157 : H7

Microbial Food Safety Research Unit, Eastern Regional Research Center, Agricultural Research Service, US Department of Agriculture, 600 East Mermaid Lane, Wyndmoor, PA, USA

Escherichia coli K-12 defends itself against peroxide-mediated oxidative damage using two catalases, KatG and KatE, and the peroxiredoxin, alkyl hydroperoxide reductase, encoded by ahpC. In E. coli O157 : H7 strain ATCC 43895 (EDL933), plasmid pO157 carries an additional catalase-peroxidase gene, katP. KatP has been shown to be a functional catalase-peroxidase. However, deletion of pO157 does not alter the peroxide resistance of strain EDL933, leaving the physiological role of katP unclear. To examine the individual roles of peroxide-resistance genes in E. coli O157 : H7, mutant strains of ATCC 43895 were constructed bearing individual deletions of katG, katE, katP and ahpC, as well as double, triple and quadruple deletions encompassing all possible gene combinations thereof. The wild-type and all 15 mutant strains were compared for differences in aerobic growth, ability to scavenge exogenous H₂O₂ and resistance to exogenous peroxides. Although KatG scavenged the most exogenous H₂O₂, KatP scavenged statistically greater amounts than either KatE or AhpC during exponential growth. However, katG and ahpC together were sufficient for full peroxide resistance in disc diffusion assays. Strains with only katG or ahpC were the only triple deletion strains with significantly shorter generation times than the quadruple deletion strain. ahpC was the only gene that could allow rapid transition from lag phase to exponential phase in a triple deletion strain. Gene expression studies revealed that katP is an OxyR-regulated gene, but its expression is suppressed in stationary phase by RpoS. These studies indicate that pO157-borne katP contributes to the complex gene network protecting strain 43895 from peroxide-mediated oxidative damage in an OxyR-dependent manner.

Correspondence
Gaylen A. Uhlich
gaylen.uhlich{at}ars.usda.gov