[Caffeine as an inhibitor of the conjugation transfer of R-factors. A study of the quantitative effect of caffeine on the conjugation transfer of R-factors].

The effect of caffeine on the conjugation transfer of R-factors was studied using a standartized kinetic conjugation system described earlier. It was shown that caffeine had a pronounced inhibitory effect on R-factor transfer. The inhibition coefficients at a caffeine concentration of 2000 gamma/ml were from 2.5 (when using strain CSH-2 R222 of E. coli as the donor) to 13.8 (when using strain J5-3 RI drd of E. coli as the donor). Higher concentrations of caffeine induced a significant increase in the coefficient. Since R-transfer inhibition was induced by rather high concentrations of caffeine, the effect of equivalent concentrations of some normal metabolites of the purine and pyrimidine series, such as ATP, guanine, cytosine and thymine was studied. It was shown that the substances had no inhibitory effect on R-factor transfer. Inhibition of P-transfer by caffeine did not depend on either the type of R-factor or the microbial host.