Synergism Between Cysteine and Alkylating Agents

Abstract

Contrary to expectation, l -cysteine did not protect Escherichia coli from the lethal action of two monofunctional alkylating agents (nitrosomethylurethane and methylmethane sulfonate). The antibacterial action of these compounds was actually greatly enhanced by l -cysteine. This synergistic effect was also exhibited, to some extent, by d -cysteine but not by homocysteine, S -methylcysteine, or serine. The synergistic action between methylating agents and l -cysteine was not due to the formation of S -methylcysteine. l -Cysteine had no effect on the bacteriostatic action of ethylmethane sulfonate.