Relationship between Sporulation Medium and Germination Ability of Mucor racemosus Sporangiospores

Abstract

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.

Role of Amino Acids and Endogenous Protein in the Germination of Mucor racemosus Sporangiospores

“…As previously reported (Tripp & Paznokas, 1981), greater than 95% of M-and C-spores of M . racernosus germinate in MGM containing glucose, peptone or Casamino acids; but no M-spores and only a portion of C-spores germinate in the presence of glutamate or alanine.…”

“…Interestingly, the addition of exogenous cyclic AMP stimulated the rate of 3-OMDG-triggered protein loss in C-spores but did not initiate it (Fig. 6), and may explain why the rate of swelling but not the percentage of a C-spore population germinating on glutamate was stimulated by cyclic AMP (Wertman & Paznokas, 1981;Tripp & Paznokas, 1981). The observation that cyclic AMP stimulates the rate of protein degradation is not unique to M .…”

“…racemosus sporangiospores average 20 pm3. Upon treatment with a suitable germinant, an increase in volume can be observed with a Coulter counter (model ZB 1) and Channelyzer (model 11) as described previously (Tripp & Paznokas, 1981). For these studies, spores that had increased to a volume >45 pm3 were considered to have initiated germination.…”

Glucose-initiated Germination ofMucor racemosus Sporangiospores

“…Effects of glucose analogues on germination Previous studies (Tripp & Paznokas, 1981) have shown that Mucor racernosus sporangiospores are initiated to germinate synchronously and completely by glucose or the glucose analogue 3-0-methyl-~-glucose. Both C-and M-spores were treated with a number of compounds that are structurally related to glucose (Table 1) in a medium which also contained yeast nitrogen base, ammonium sulphate and glutamate.…”

“…Sporangiospore volume was monitored with a Coulter counter (model ZB 1) and Channelyzer (model 11) as previously described (Tripp & Paznokas, 1981). Greater than 90% of either M-spores or C-spores have a volume (45 pm3 at the time of harvesting.…”