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Glucose, galactose and fructose uptake was studied during the germination of Streptomyces antibioticus spores. Dormant spores had only the glucose uptake system, whatever the carbon source of the sporulation medium. Even when sporulation took place in the presence of galactose or fructose as the sole carbon and energy source neither galactose nor fructose uptake was detected. During germination the uptake systems for these two sugars were inducible by the appropriate sugar; the induction time was less when the germination process was more advanced. Synthesis of all uptake systems was immediately blocked by the addition of inhibitors of protein or RNA synthesis. Vegetative mycelium in the exponential phase of growth showed a similar pattern of sugar uptake. Glucose caused repression of the galactose and fructose uptake systems. The three sugar uptake systems were strongly inhibited by potassium cyanide, 2,4-dinitrophenol and p-chloromercuribenzoate, and showed optimum temperatures for uptake at 40°C (glucose) and 45 °C (galactose and fructose).