GALACTOSE TRANSPORT IN CLOSTRIDIUM-ACETOBUTYLICUM P262

Evidence is provided that there are two separate systems for galactose uptake in Clostridium acetobutylicum P262, a phosphoenolpyruvate-depe ndent phosphotransferase system and a proton motive force-driven syste m. Glucose uptake involves the former but not the latter. When present on their own in a semi-synthetic medium, glucose and galactose were c onsumed by the bacterium at rates of 1.00 mmol l(-1) h(-1) and 0.79 mm ol l(-1) h(-1), respectively. However, when present as a mixture, gluc ose was used preferentially, and there was a lag period before galacto se utilization commenced. The subsequent consumption rates were 0.97 m mol l(-1) h(-1) and 0.38 mmol l(-1) h(-1), for glucose and galactose, respectively. These data provide evidence for repression of galactose utilization by glucose.