INHIBITION OF R-FACTOR TRANSFER AND PHAGE INFECTION BY REQUINOMYCIN

To be effective in inhibiting R-factor transfer (between Escherichia coli strains) and infection of E. coli with phage f 2, requinomycin must be present at the time of initiation of both events. Delayed addition of requinomycin showed no or slight inhibition. No direct effect of requinomycin on phage f2 or E. coli strains employed was observed. The intact cell surface of E. coli must be impermeable to requinomycin as shown by the fact that DNA synthesis by toluene-treated E. coli cells (permeability modified) was markedly inhibited by requinomycin, in contrast to its ineffectiveness on intact E. coli cells. Therefore, requinomycin probably acts without penetrating the cells. Probable mechanism of action is discussed.