SUMMARYThe morphological effect of potassium cyanide on the aerobic germination of spores of Mucor rouxii (NRRLI 894) in the presence of glucose was investigated. At concentrations of up to 2 mM-KCN, normal filaments were formed; at concentrations of 3 to 6 mM intermediate forms were observed ranging from enlarged and septated hyphae to rounded multipolar cells; at 8 mM spores produced only budding spherical cells. The effect of glucose on the anaerobic germination of spores was also studied. At 0.01 % glucose hyphal development occurred, whereas at increasing concentrations dimorphic colonies were formed. At 2 % glucose purely yeast colonies appeared of the type described by Bartnicki-Garcia (1968) for Mucor rouxii Y M~O . In the absence of glucose, or when glucose was replaced by xylose, maltose or succinate, spores did not germinate.Anaerobiosis did not prevent the elongation of preformed hyphae obtained under aerobic conditions, provided that the cellular integrity was maintained. The anaerobic mycelia had a fermentative metabolism, as indicated by the low level of cytochrome oxidase, the amount and the type of pyruvate kinase, and the production of ethyl alcohol. Conversion of hyphal to yeast-like morphology was observed when tips of young hyphae were cultured in conditions favouring fermentation. The budding cells obtained were indistinguishable from yeast-like cells generated by anaerobic germination of spores.

Pyruvate kinase from Mucor rouxii constitutes a family of three isoenzymes which can be separated in DEAE-cellulose columns. These have been named type I, I1 and 111. They also have different electrophoretic mobility in polyacrylamide gels. Pyruvate kinases type I, I1 and I11were partially purified by ion-exchange chromatography. Antisera were prepared against types I and 111. The antigenic behaviour of the three isoenzymes supported the hypothesis on the hybrid nature of pyruvate kinase type I1 and confirmed the identity of pyruvate kinase from yeastlike cells and type I from mycelium.The filamentous form contains the three types, none of them being constitutive and the proportion of each depends on the concentration and on the nature of the carbohydrate in the growth medium. Under gluconeogenic conditions of growth type 111 predominantes while in any condition in which aerobic glycosis is favoured type I is the dominant form. We also show the results of a detailed study of the effects of nutritional factors on the enzymatic pattern of pyruvate kinases in M . rouxii.Evidence is presented indicating that under a variety of conditions the filamentous form contains the three forms of the enzyme, which can be distinguished from each other on DEAE-cellulose columns. None of the three forms seems to be constitutive, the relative proportions of each form vary according to the growing conditions as well as to the morphology of the fungus. Kinetics of induction of pyruvate kinase I1 and I11 during aerobic germination of spores under gluconeogenic conditions, accompanied by disappearance of type I and also reappearance of types I and I1 upon addition of glucose or xylose to growing cultures devoid

No abstract

No abstract