Peroxide resistance in Escherichia coli serotype O157 : H7 biofilms is regulated by both RpoS-dependent and -independent mechanisms.
In many Escherichia coli serotype O157 : H7 strains, defences against peroxide damage include the peroxiredoxin AhpCF and three catalases: KatG (catalase/peroxidase), KatE (catalase) and the plasmid-encoded KatP (catalase/peroxidase). AhpC and KatG basal expression is maintained by RpoS, and AhpC, KatG and KatP are all induced by OxyR/σ(70) in exponential phase. KatE is regulated by RpoS during stationary growth and is independent of OxyR. In a previous study we used mutant strains of ATCC 43895 (EDL933) with deletions of katG, ahpC, katE and katP in all possible combinations to characterize peroxide resistance during both exponential and 18-24 h growth in Luria-Bertani broth at 37 °C. In this study, we used triple deletion strains that isolated each catalase/peroxidase gene to investigate their role in the peroxide resistance of biofilm-forming variant 43895OR in 48 and 72 h biofilms. We also used quantitative real-time reverse transcriptase PCR and translational lacZ fusions to study gene expression. Peroxide resistance was greater (P<0.05) in biofilm cells than in planktonic cells, and full resistance required rpoS but not oxyR. In 72 h biofilms, katG and katE were the major protective genes. katG, ahpC and katE peroxide protection had both rpoS-dependent and rpoS-independent components, but katP protection was independent of rpoS. H(2)O(2) challenge induced (P<0.05) katG, ahpC and katP expression in biofilm cells, suggesting that peroxide induction of the OxyR-dependent resistance genes may contribute to the RpoS-independent protection in Shiga toxin-producing E. coli biofilms.
Molecular Characterization of Foodborne Pathogens Research Unit, Eastern Regional Research Center, Agricultural Research Service, US Department of Agriculture, 600 East Mermaid Lane, Wyndmoor, PA, USA.
Gaylen A
GA
Uhlich
Molecular Characterization of Foodborne Pathogens Research Unit, Eastern Regional Research Center, Agricultural Research Service, US Department of Agriculture, 600 East Mermaid Lane, Wyndmoor, PA, USA.
Chin-Yi
CY
Chen
Molecular Characterization of Foodborne Pathogens Research Unit, Eastern Regional Research Center, Agricultural Research Service, US Department of Agriculture, 600 East Mermaid Lane, Wyndmoor, PA, USA.
Bryan J
BJ
Cottrell
Molecular Characterization of Foodborne Pathogens Research Unit, Eastern Regional Research Center, Agricultural Research Service, US Department of Agriculture, 600 East Mermaid Lane, Wyndmoor, PA, USA.
Peter L
PL
Irwin
Molecular Characterization of Foodborne Pathogens Research Unit, Eastern Regional Research Center, Agricultural Research Service, US Department of Agriculture, 600 East Mermaid Lane, Wyndmoor, PA, USA.
John G
JG
Phillips
D019677:Artificial Gene Fusion; D001426:Bacterial Proteins / Q000378:metabolism*; D018441:Biofilms / Q000187:drug effects*; D002374:Catalase / Q000235:genetics / Q000378:metabolism; D024881:Drug Resistance, Bacterial; D019453:Escherichia coli O157 / Q000187:drug effects* / Q000502:physiology*; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial; D017930:Genes, Reporter; D050296:Microbial Viability / Q000187:drug effects; D016877:Oxidants / Q000633:toxicity; D018384:Oxidative Stress; D010545:Peroxides / Q000633:toxicity*; D054464:Peroxiredoxins / Q000235:genetics / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D012808:Sigma Factor / Q000378:metabolism*; D013312:Stress, Physiological; D014158:Transcription, Genetic; D001616:beta-Galactosidase / Q000032:analysis / Q000235:genetics
D001426:Bacterial Proteins; D016877:Oxidants; D010545:Peroxides; D012808:Sigma Factor; C069567:sigma factor KatF protein, Bacteria; D054464:Peroxiredoxins; D002374:Catalase; D001616:beta-Galactosidase