The influence of altered plasma membrane fatty acid composition on cesium uptake and toxicity was investigated in Saccharomyces cerevisiae. Detailed kinetic studies revealed that both the Vmaxand Kmvalues for Cs+transport increased (by approximately twofold in the latter case) when S. cerevisiae was grown in medium supplemented with the polyunsaturated fatty acid linoleate. In addition, Cs+uptake by linoleate-enriched cells was considerably less sensitive to the competitive effects of other monovalent cations (K+, Rb+, and NH4+) than that by unsupplemented cells. Stimulation of Cs+uptake in the presence of certain K+and Rb+concentrations was only evident in linoleate-enriched S. cerevisiae. At 100 mM CsCl, the initial rate of Cs+uptake was greater in linoleate-supplemented cells than in unsupplemented cells and this was reflected in a more rapid displacement of cellular K+. However, little difference in net Cs+accumulation between linoleate-supplemented and unsupplemented cells was evident during prolonged incubation in buffer or during growth. Thus, Cs+toxicity was similar in linoleate-supplemented and unsupplemented cells. The results were consistent with the Cs+(K+) transport mechanism adopting an altered conformational state in linoleate-enriched S. cerevisiae.Key words: monovalent cation transport, plasma membrane fatty acid composition, lipid–protein interactions, metal–microbe interactions, cation competition.
Assessment of Plasma Membrane Fatty Acid Composition and Fluidity Using Imaging Flow Cytometry
