As an adaptation process to the growth retardation provoked by the presence of nonlethal concentrations of ergosterol biosynthesis inhibitors, Ustilago maydis alters the ratio of linoleic to oleic acid bound to plasma membrane ´ complex lipids [Hernandez, A., Cooke, ., Lewis, M. & Clarkson, . (1997) Microbiology 143, 3165–3174]. This alteration increases plasma membrane H+-ATPase hydrolytic activity.