Relationship between sporulation medium and germination ability of Mucor racemosus sporangiospores.

Asexual sporangiospores of Mucor racemosus produced on a minimal sporulation medium (M spores) germinated only if glucose, mannose or a complex substrate such as peptone, yeast extract or Casamino acids was present. Once germinated, growth was supported by a wide range of substrates including amino acids, carbohydrates or organic acids. Sporangiospores produced on a nutritionally complex sporulation medium (C-spores) germinated on a wide range of carbon sources. C-spore phenotype was pleiotropic in that sporangiospores capable of germinating on cellobiose could always germinate on glutamate or xylose; but C-spores capable of germinating on xylose or glutamate did not always germinate on cellobiose. There was a hierarchy of substrates capable of initiating germination with glucose = mannose greater than xylose greater than glutamate greater than cellobiose. C-spores also differed from M-spores by initiating germination in the presence of the non-metabolizable glucose analogue 3-O-methylglucose. These results suggest that at least two sporangiospore phenotypes are produced depending upon the concentration and type of ingredients present in the sporulation medium.