title: Influence of polyphenols on Escherichia coli resistance to oxidative stress.
abstract: Among all polyphenols tested (tannic acid and flavonoids belonging to different subclasses) only tannin and quercetin significantly enhanced resistance of Escherichia coli to peroxide stress. Pretreatment of the cells with quercetin and tannin resulted in a decrease in the growth arrest duration under moderate H(2)O(2) concentration (2 mM) and an increase in survival under high (10 mM) doses. The shorter growth recovery period in pretreated cells was connected with more rapid H(2)O(2) elimination because of induced activity of scavenging enzymes. This effect was absent in the Delta oxyR mutant, which was unable to induce genes responding to peroxide stress. The data obtained suggest that the observed protection was a result of two overlapping effects: induction of OxyR regulon by low concentrations of H(2)O(2), accumulated during extracellular autoxidation of quercetin and tannin, and protection of synthesis of OxyR-regulated antioxidant enzymes during H(2)O(2) stress because of intracellular binding of iron by quercetin and tannin and suppressing Fenton chemistry.
authors.affiliation: Institute of Ecology and Genetics of Microorganisms, Russian Academy of Sciences, Golev Street 13, Perm 614081, Russia. smirnova@iegm.ru
authors.forename: Galina V
authors.initials: GV
authors.lastname: Smirnova
authors.forename: Zoya Y
authors.initials: ZY
authors.lastname: Samoylova
authors.forename: Nadezda G
authors.initials: NG
authors.lastname: Muzyka
authors.forename: Oleg N
authors.initials: ON
authors.lastname: Oktyabrsky
mesh_terms: D000975:Antioxidants / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects; D004926:Escherichia coli / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D006861:Hydrogen Peroxide / Q000378:metabolism; D009154:Mutation; D018384:Oxidative Stress / Q000187:drug effects*; D011794:Quercetin / Q000494:pharmacology*; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D013482:Superoxide Dismutase / Q000378:metabolism; D013634:Tannins / Q000494:pharmacology*; D001616:beta-Galactosidase / Q000378:metabolism
chemical_list: D000975:Antioxidants; D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D012097:Repressor Proteins; D013634:Tannins; C499299:oxyR protein, E coli; D011794:Quercetin; D006861:Hydrogen Peroxide; C095500:SodA protein, Bacteria; D013482:Superoxide Dismutase; D001616:beta-Galactosidase