Inhibitors of energy-dependent efflux of the fungicide fenarimol by Aspergillus nidulans

Fenarimol is a fungicide classified as a sterol biosynthesis inhibitor (SBI). Its passive influx in mycelium of wild-type and SBI-resistant strains of Aspergillus nidulans is counteracted by an energy-dependent efflux. Sodium orthovanadate, the ionophores nigericin and valinomycin, and the cationic agents Cu 2+, cetylpyridinium bromide, and dodine inhibit the energy-dependent efflux of fenarimol and thus allow this fungicide to accumulate in mycelium of both wild-type and SBI-resistant strains. The ionophore gramicidin and anionic and neutral detergents had the opposite effect. It is suggested that fenarimol efflux is mediated by the electrochemical proton gradient across the fungal plasma membrane.