“…Two phenomena that lower the energy status of the cell could account for these effects. Firstly, the presence of toxic levels of toluene severely perturbs the membrane, bringing about the passive flux of protons across the membrane (Fay and Farias, 1977; Leao and Van Uden, 1984; Cartwright et al ., 1986; Sikkema et al ., 1994), thus dissipating the PMF (Cartwright et al ., 1986; Sikkema et al ., 1994). Secondly, toluene induces expression of the solvent‐resistance pump SrpABC (Kieboom et al ., 1998a,b), which is a proton‐dependent solvent‐efflux system (Isken and de Bont, 1996; Isken et al ., 1999).…”