Regulation of Termitomyces clypeatus protoplast regeneration by Krebs cycle acids

Mycelial derived protoplasts of the mushroom, Termitomyces clypeatus, did not regenerate in synthetic growth medium but did regenerate if casein hydrolysate was added to the same medium. Aspartic acid, glutamic acid, histidine, of serine and alanine when added individually had a similar effect on regeneration to that of casein hydrolysate. Krebs cycle acids also supported protoplast regeneration in the presence of glucose. Glucose alone, in the regenerating medium supported osmotically stable germ tube formation from protoplasts while Krebs cycle acid alone could not even change the osmotic fragility of the protoplasts. Electron microscopy of germ tube preparations indicated the presence of an incomplete wall structure when regeneration took place in the presence of glucose alone.