EFFECT OF CARBON SOURCE AND PH OF THE GROWTH-MEDIUM ON SPORE GERMINATION IN PHYCOMYCES-BLAKESLEEANUS

Phycomyces blakesleeanus sporangiospores responded differently to acti vation by physical and chemical stimuli. Spores that were physically ( heat shock) activated or chemically (ammonium acetate) activated germi nated and grew at pH 4.5 with the hexoses glucose, fructose, galactose , and N-acetylglucosamine, and with glycerol and amino acids. Under th ese conditions, physically activated spores showed a lower, although s ignificant growth with the hexoses fructose, galactose, N-acetylglucos amine and with glycerol. On the other hand, physically activated spore s incubated at alkaline pH (pH 7.3) required glucose to germinate; a r equirement not observed with chemically activated spores, which showed significant growth in the other hexoses tested. Both physically and c hemically activated spores incubated at pH 7.3 were unable to germinat e and grow with amino acids and glycerol. These results suggest that t here are different targets for activation of the spores by physical an d chemical treatments. The levels of the fermentative enzymes alcohol dehydrogenase and lactate dehydrogenase and of the oxidative enzyme NA D(+)-isocitrate dehydrogenase were higher in cells grown at pH 4.5 in medium containing glucose; however, alcohol dehydrogenase and lactate dehydrogenase appear not to be affected by a change in the pH of the g rowth medium.