NUTRITION, GROWTH, AND MORPHOGENESIS OF MUCOR ROUXII

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Abstract
Mucor rouxii was grown under three different atmospheres of incubation: air, N2, and CO2 in parallel cultures. The atmosphere of incubation markedly affected nutritional requirements, growth, and morphogenesis. Absence of oxygen greatly reduced growth and increased the nutritional demands of the fungus. Presence of a high tension of CO2 resulted in a change from filamentous to yeastlike morphogenesis. Aerobically, a large variety of carbon sources was utilized; anaerobically, only hexoses served to meet requirements for carbon and energy. Aerobically, various amino acids supported abundant growth; anaerobically, they were poorly utilized. Ammonium and nitrate ions were better sources of nitrogen for anaerobic growth. In general, incubation under either air or N2 resulted in development of coenocytic filamentous mycelium, whereas incubation under CO2 resulted in development of budding yeastlike cells. Variations in temperature and time of incubation, inoculum size, type and concentration of carbon source, type of nitrogen source, and presence of various substances with known action on fungal morphogenesis altered growth in many cases, but did not significantly affect the patterns of vegetative morphogenesis conditioned by each atmosphere of incubation. However, vegetative morphogenesis was strongly affected by addition of certain chelating agents. Yeastlike development of M. rouxii was prevented by ethylenediaminetetraacetic acid (EDTA) in concentrations which are also partially inhibitory for growth; under these conditions, development was filamentous. Chemically related chelating agents were similarly active. The growth-inhibitory and morphogenetic effects of EDTA were reversed by transition-group metal ions. Yeastlike development of M. subtilissimus. which does not require CO2 for its induction, was also inhibited by EDTA.
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