ABSTRACT
Prokaryotic microorganisms also possess several important advantages over eukaryotic cells, specifically for investigations of membrane permeability and transport processes. This chapter summarizes and critically evaluates the effect of membrane lipids on the movement of molecules across the membranes of prokaryotic microorganisms. It focuses on the relationship between membrane lipid fluidity and phase state and passive permeability and various protein-mediated transport processes. The chapter discusses the definition and measurement of membrane lipid fluidity and phase state and of the interpretation of diffusional and transport experiments. For membrane- associated transport systems and enzymes, however, nonlinear Arrhenius plots are often obtained. A careful examination of the Arrhenius plot of antibiotic transport reveals that, in fact, the experimental points fall on a single, slightly curving line. Thus, the assignment of discrete transport break temperatures seems quite arbitrary, and for this reason the significance of this study is unclear.
