Hyphal tip growth in Achlya: Enzyme activities in mycelium and medium
Achlya ambisexualis Raper is a coenocytic, hyphal water mold which exhibits apical vegetative growth when cultured on a denned liquid medium. Upon transfer to a medium containing only glucose, growth is reduced considerably as measured by changes in fresh weight, incorporation of exogenous glucose into hyphal walls, and secretion of cellulase. Of the enzymes tested, only cellulase and alkaline phosphatase exhibit higher specific activities in growing mycelia than in nongrowing mycelia; the specific activity of UDPG transferase remains about the same. All enzyme activities found in mycelial extracts also were present in the culture filtrate. The only enzymes showing much higher activities in the filtrate than in the mycelium were ATPase and cellulase. Possible roles for cellulase during growth are discussed.