Effect of Potassium Cyanide, Glucose and Anaerobiosis on Morphogenesis of Mucor rouxii

Abstract

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.

Protein Synthesis During Morphogenesis of Mucor racemosus

“…Thus molecular oxygen and presumably the energy generated by aerobic metabolism do not directly induce the response. Cyanide, 2,4-dinitrophenol, and other inhibitors or uncouplers of oxidative phosphorylation have been reported to interfere with energy metabolism in this and related organisms (6,8,20,21), but they also keep the cells in the yeast forn and therefore were not tested. Mucor can on August 17, 2020 by guest http://jb.asm.org/ Downloaded from grow in either yeast or hyphal form in N2, depending on the flow rate of the gas.…”

Mucor dimorphism.

“…Substances that inhibit mitochondrial energy-generating functions such as electron transfer (e.g., potassium cyanide and antimycin A) and oxidative phosphorylation (e.g, oligomycin) lock Mucor spp., or their relatives the Mycotypha spp., into the yeast form under aerobic conditions (73,199). Similarly, chloramphenicol, which inhibits protein synthesis on 70S ribosomes and thus prevents the production of cytochrome oxidase, cytochrome b, and other key components of the mitochondrion, constrains growth of Mucor spp.…”

“…Several different experimental approaches have been employed in the attempt to collect evidence supportive of a link between Mucor morphology and the mode of carbon and energy metabolism. Inhibitors of electron transport or oxidative phosphorylation in mitochondria (73) and inhibitors of protein synthesis within mitochondria (238) constrain growth of dimorphic Mucor spp. to the yeast phase.…”

Calcineurin Plays Key Roles in the Dimorphic Transition and Virulence of the Human Pathogenic Zygomycete Mucor circinelloides

“…Although dimorphic Mucor species vary in their responses to the environment during morphogenic changes, common critical factors that induce yeast growth of Mucor species include oxygen concentration, CO 2 concentration, and carbon source (reviewed in [12]). In addition, several chemicals that inhibit mitochondrial function [including potassium cyanide and antimycin A (which block electron transport) or oligomycin and phenyl alcohol (which inhibit oxidative phosphorylation)] induce yeast growth in Mucor spp., even in aerobic conditions [18]–[20]. Inhibition of the synthesis of cytochrome b and other mitochondrial components by chloramphenicol also results in Mucor yeast growth [21], [22].…”