1887

Abstract

K-12 defends itself against peroxide-mediated oxidative damage using two catalases, KatG and KatE, and the peroxiredoxin, alkyl hydroperoxide reductase, encoded by . In O157 : H7 strain ATCC 43895 (EDL933), plasmid pO157 carries an additional catalase-peroxidase gene, . 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 unclear. To examine the individual roles of peroxide-resistance genes in O157 : H7, mutant strains of ATCC 43895 were constructed bearing individual deletions of , , and , 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 HO and resistance to exogenous peroxides. Although KatG scavenged the most exogenous HO, KatP scavenged statistically greater amounts than either KatE or AhpC during exponential growth. However, and together were sufficient for full peroxide resistance in disc diffusion assays. Strains with only or were the only triple deletion strains with significantly shorter generation times than the quadruple deletion strain. 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 is an OxyR-regulated gene, but its expression is suppressed in stationary phase by RpoS. These studies indicate that pO157-borne contributes to the complex gene network protecting strain 43895 from peroxide-mediated oxidative damage in an OxyR-dependent manner.

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2009-11-01
2024-03-28
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