Effect of antibiotics influencing membrane function on the potassium transport of E. coli cells.

The effect of polymixin, nigericin, gramicidin on the 42K-efflux of E. coli cells was studied. The 42K-efflux of the bacteria decreases in time according to an exponential function. The slopes of the linearized functions characterizing the efflux increase with increasing concentration of antibiotics. The frequency of events of the 42K-release as a parameter of antibiotics membrane interaction was determined on the basis of a theoretical model developed for the evaluation of our experimental data. In this way a quantitative comparison of the effectiveness of antibiotics was possible. We found, that the most effective antibiotic was polymixin, followed by nigericin and gramicidin.