Effects of penetrating and non-penetrating oxidants on Escherichia coli.

Treatment of Escherichia coli K-12 cells aerobically grown in M9 glucose salt medium (H2O2) and non-penetrating (ferricyanide) oxidants resulted in similar inhibition of growth and decrease in intracellular K+ pool by 15%. Only H2O2 inhibited growth of auxotrophic strains grown in M9 medium supplemented with protein hydrolysate. Ferricyanide reduction was associated with decrease in low-molecular-weight thiols, whereas the treatment of cells with H2O2 increased their level. Pretreatment of cells with ferricyanide enhanced the H2O2-induced expression of katG gene encoding for catalase HPI; this gene is a member of the gene family controlled by the oxyR gene. Pretreatment with ferricyanide inhibited H2O2-induced expression of the sfiA gene which is the member of the gene family controlled by the recA and lexA genes. Glutathione is the major low-molecular-weight thiol in E. coli, and it can play different roles in cellular responses to H2O2 and ferricyanide.