UNCOUPLER-RESISTANT GLUCOSE-UPTAKE BY THE THERMOPHILIC GLYCOLYTIC ANAEROBE THERMOANAEROBACTER-THERMOSULFURICUS (CLOSTRIDIUM-THERMOHYDROSULFURICUM)

The transport of glucose across the bacterial cell membrane of Thermoa naerobacter thermsulfuricus (clostridium thermohydrosulfuricum) Rt8.B1 was governed by a permease which did not catalyze concomitant substra te transport and phosphorylation and thus was not a phosphoenolpyruvat e-dependent phosphotransferase. Glucose uptake was carrier mediated, c ould not be driven by an artificial membrane potential (DETLApsi) in t he presence or absence of sodium, and was not sensitive to inhibitors which dissipate the proton motive force (DELTAp; tetrachlorosalicylani lide, N,N-dicyclohexylcarboiimide, and 2,4-dinitrophenol), and no upta ke of the nonmetabolizable analog 2-deoxyglucose could be demonstrated . The glucokinase apparent K(m) for glucose (0.21 mM) was similar to t he K(t) (affinity constant) for glucose uptake (0.15 mM), suggesting t hat glucokinase controls the rate of glucose uptake. Inhibitors of ATP synthesis (iodoacetate and sodium fluoride) also inhibited glucose up take, and this effect was due to a reduction in the level of ATP avail able to glucokinase for glucose phosphorylation. These results indicat ed that T. thermosulfuricus Rt8.B1 lacks a concentrative uptake system for glucose and that uptake is via facilitated diffusion, followed by ATP-dependent phosphorylation by glucokinase. In T. thermosulfuricus Rt8.B1, glucose is metabolized by the Embden-Meyerhof-Parnas pathway, which yields 2 mol of ATP (G. M. Cook, unpublished data). Since only 1 mol of ATP is used to transport 1 mol of glucose, the energetics of t his system are therefore similar to those found in bacteria which poss ess a phosphotransferase.