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

Abstract

The role of amino acids as triggers of Mucor racemosus sporangiospore germination was investigated. No single amino acid was effective as glucose or peptone at triggering germination. Germination induced by glucose or peptone was pH-independent, whereas germination induced by glutamate was pH-dependent. The composition of the free amino acid pools of M-spores (those unable to germinate on glutamate) was qualitatively and quantitatively similar to that of C-spores (those capable of germinating on glutamate) with the exceptions of hydroxyproline and methionine and methionine whose concentrations were several-fold higher in C-spores. Glutamate and leucine were taken up by germinating and nongerminating spores; however, significant protein synthesis occurred only in germinating spores. Spores not triggered by 3-O-methyl-D-glucose (M-spores) contained about one-half the protein of those triggered by 3-O-methyl-D-glucose (C-spores). C-spores initiated to germinate by 3-O-methyl-D-glucose decreased in total organic carbon and protein over a 6 h period; removal of the 3-O-methyl-D-glucose resulted in an immediate halt of protein degradation and spore swelling. These results suggest that protein is a major endogenous reserve in M. racemosus sporangiospores and that its turnover is a necessary event for glucose-triggered germination.

Effect of individual amino acids and glucose on activation and germination of Rhizopus oligosporus sporangiospores in tempe starter

“…It should be noted that we observed only a slight uptake of l ‐leucine (data not shown), which is in good agreement with earlier publications (Tripp and Paznokas 1982b).…”

“…It should be noted that we observed only a slight uptake of L L-leucine (data not shown), which is in good agreement with earlier publications (Tripp and Paznokas 1982b). As was mentioned above, L L-proline could activate dormant spores and stimulate formation of germ tubes, but it did not support their outgrowth to colonies.…”

Mucor dimorphism.

“…The influence of L-amino acids on dimorphism and sporangiospore germination was examined in M. rouxii (126) and M. racemosus (225). Certain amino acids were more effective than others in stimulating germination when offered as the sole carbon source (225).…”

“…Some amino acids favored growth in the yeast morphology, whereas others favored growth in the hyphal form when offered as the sole nitrogen source (126). The pH influenced both morphological responses (126,225). There is presently no single theory that satisfactorily explains the diverse effects of amino acids on Mucor morphogenesis.…”

Differential gene expression during aerobic germination of Mucor racemosus sporangiospores

“…When placed ihto a hexose-containing nutrient medium under CO2 or N2, for example, the sporangiospore carries out an essentially equivalent amount of spherical growth before initiating the formation of multipolar buds. Several previous studies have dealt with the aerobic germination of Mucor sporangiospores (13,18,19,21,(27)(28)(29)33), and this is the system of development we have focused upon in the present work.…”