Nutrient utilization and transport in the thermoacidophilic archaeon Sulfolobus shibatae

Department of Biochemistry and Molecular Biology, Royal Free Hospital School of Medicine, University of London, Rowland Hill Street, London NW3 ZPF, UK Growth of the thermoacidophilic archaeon Sulfolobus shibatae was tested on a range of carbon and nitrogen sources. Optimal defined and complex growth media were developed and growth conditions in both shake flask and fermenter cultures were optimized. Better growth was observed on maltose in particular and disaccharides in general than on monosaccharides. Moreover, maltose utilization was not repressed in the presence of glucose which suggests that glucose is not the preferred substrate of S. shibatae. Uptake studies putatively identified two saturable, constitutive maltose transport systems, a high-aff inity, possible membrane-binding system with a Km of 20 pM and a Vof 218 nmol min-l (mg protein)-l, and a low-aff inity, protondependent system with a Km of 158 pM and a VmuI of 680 nmol min-l (mg protein)-l. Both systems showed differential responses to treatment with 2,4 dinitrophenol and arsenate, and differed from other maltose transport mechanisms described in being constitutive under all conditions tested and not repressed by glucose.