A Dactylium dendroides morphological mutant defective in D-galactose metabolism.

1. A morphological mutant of the mold Dactylium dendroides was isolated and the phenotype characterized as D-Gal- and L-Ara-. 2. The transport system for D-galactose seemed to be inducible in wild type and mutant and was altered in the mutant. 3. Galactose-1-P-uridylyl transferase activity was absent in the mutant. 4. The levels of intracellular galactose oxidase activity were similar in the wild type and in the mutant, thereby excluding a possible participation of this enzyme in galactose catabolism in the mold. 5. The low level of galactose oxidase activity found in the extracellular medium indicates a defect in galactose oxidase secretion by the mutant.