The effect of colicin El on proton extrusion and the H +/O ratio in Escherichiacoli

Abstract

Summary The addition of a small pulse of oxygen to an anaerobic suspension of colicin sensitive E . coli B/1,5 cells induces a relatively small, slowly reversible extrusion of protons by the cells into the medium. Pretreatment of the cells with colicins El and K greatly accelerates the rate of proton extrusion as well as the rate of decay of the measured pH change, while increasing the amplitude of the H+/O ratio from 2.0. Colicin El had no effect on the proton extrusion or H+/O ratio in the tolerant E . coli strain A586. These effects suggest that, in the presence of colicins El and K, the E . coli cell envelope becomes freely permeable to a counterion and is therefore no longer able to maintain a membrane electrical potential.