Respiratory Capacity, Cyclic Adenosine 3',5'-monophosphate, and Morphogenesis of Mucor Racemosus

A variety of cultural conditions were examined to determine the relationship between respiratory capacity and the growth of Mucor racemosus in the yeast and mycelial form. The results show that both yeasts and hyphae can develop when the respiratory capacity is low (e.g., in N2). In addition, the yeast form of the fungus could be grown in air in the presence of cyclic adenosine 5'-monophosphate with high respiratory rates characteristic of air-grown mycelia. These results indicate that their is not an obligatory relationship between respiratory capacity and morphogenesis in M. racemosus. Low intracellular levels of cyclic adenosine 5'-monophosphate, however, were correlated with aerobic mycelial development, whereas yeast development under CO2 was characterized by higher cyclic adenosine 5'-monophosphate levels.