Title: Understanding the role of the catalase/peroxide genes in H2O2 resistance of E. coli serotype O157:H7 biofilms Authors
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: March 6, 2012
Publication Date: July 25, 2012
Citation: Uhlich, G.A., Chen, C., Irwin, P.L. 2012. Understanding the role of the catalase/peroxide genes in H2O2 resistance of E. coli serotype O157:H7 biofilms [abstract]. 1:1. Technical Abstract: Introduction: Escherichia coli serotype O157:H7 defenses against H2O2 include the peroxiredoxin AhpC and three catalases: KatG (catalase-peroxidase), KatE (catalase), and the plasmid-encoded KatP (catalase/peroxidase). AhpC, KatG, and KatP are induced by OxyR in exponential phase, while KatE is induced by RpoS and independent of OxyR. In stationary phase, basal expression of KatG and AhpC are also maintained by RpoS. Purpose: In this study we investigated the role and regulation of each catalase/peroxidase in the H2O2 resistance of a biofilm forming variant of strain EDL933 (43895OR) residing in a single-species biofilm. Methods: We constructed mutants of isolate 43895OR with deletion of rpoS, oxyR, both oxyR/rpoS, or with deletions of 3 of the 4 peroxide scavenging enzymes. Strains bearing only katG, katP, ahpC or katE were compared to a strain with deletion of all four genes and to the wild-type for survival differences following H2O2 challenge. rpoS deletions constructed in each of the strains bearing a single catalase/peroxidase gene defined the regulatory influence of RpoS. Results: Strain 43895OR survival was greater (P<0.05) in biofilm than in planktonic cells, and full resistance required rpoS but not oxyR. In 72-h biofilms, katG and katE provided the most protection, with katG able to maintain full resistance. Each mutant bearing a single resistance gene survived under reduced O2 conditions, but their counts were significantly lowered (P<0.05) in the absence of RpoS. In contrast, RpoS deletion was lethal in a strain missing all four resistance genes indicating that all four resistance genes provide some RpoS-independent peroxide resistance in biofilms. Significance: This is the first study of the role and regulation of the major peroxide resistance genes in E. coli serotype O157:H7 biofilms. Understanding the mechanism and regulation of peroxide resistance in biofilms will aid in developing intervention strategies for the control of E. coli O157:H7.