title: Potentiation by L-cysteine of the bactericidal effect of hydrogen peroxide in Escherichia coli.
abstract: Under anaerobic conditions an exponentially growing culture of Escherichia coli K-12 was exposed to hydrogen peroxide in the presence of various compounds. Hydrogen peroxide (0.1 mM) together with 0.1 mM L-cysteine or L-cystine killed the organisms more rapidly than 10 mM hydrogen peroxide alone. The exposure of E. coli to hydrogen peroxide in the presence of L-cysteine inhibited some of the catalase. This inhibition, however, could not fully explain the 100-fold increase in hydrogen peroxide sensitivity of the organism in the presence of L-cysteine. Of other compounds tested only some thiols potentiated the bactericidal effect of hydrogen peroxide. These thiols were effective, however, only at concentrations significantly higher than 0.1 mM. The effect of L-cysteine and L-cystine could be annihilated by the metal ion chelating agent 2,2'-bipyridyl. DNA breakage in E. coli K-12 was demonstrated under conditions where the organisms were killed by hydrogen peroxide.
mesh_terms: D015082:2,2'-Dipyridyl / Q000494:pharmacology; D000332:Aerobiosis; D000693:Anaerobiosis; D002374:Catalase / Q000037:antagonists & inhibitors / Q000378:metabolism; D003545:Cysteine / Q000494:pharmacology*; D003553:Cystine / Q000494:pharmacology; D004269:DNA, Bacterial / Q000378:metabolism; D004357:Drug Synergism; D004926:Escherichia coli / Q000187:drug effects* / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D008670:Metals / Q000494:pharmacology
chemical_list: D004269:DNA, Bacterial; D008670:Metals; D003553:Cystine; D015082:2,2'-Dipyridyl; D006861:Hydrogen Peroxide; D002374:Catalase; D003545:Cysteine