This 1982 study investigates how glucose triggers germination of Mucor racernosus sporangiospores. Researchers examined two spore types grown on different media: C-spores (complex medium) and M-spores (minimal medium). Both spore types were induced to germinate by glucose and certain glucose analogues, particularly mannose, 3-O-methyl-D-glucose, 5-thio-D-glucose, and 6-deoxy-D-glucose. The germination rate depended on the concentration of the triggering compound, with similar kinetic constants for glucose and 3-O-methyl-D-glucose. Importantly, spores accumulated various glucose analogues including non-triggering compounds like 1-O-methyl-D-glucose, indicating that uptake alone does not determine triggering capacity. Chromatographic analysis revealed that 3-O-methyl-D-glucose was not metabolized during germination. The germination process required continued presence of the trigger molecule and protein synthesis, as demonstrated by cycloheximide inhibition studies. These findings support the hypothesis that glucose acts as a specific effector molecule triggering spore germination through a non-metabolic mechanism, likely involving stereospecific interaction with a regulatory protein rather than glucose catabolism.

Key findings

• Glucose and structurally similar analogues (mannose, 3-O-methyl-D-glucose, 5-thio-D-glucose, 6-deoxy-D-glucose) specifically trigger M. racernosus sporangiospore germination in a concentration-dependent manner
• 3-O-methyl-D-glucose triggers germination without being metabolized, demonstrating that glucose acts as a non-metabolizable trigger molecule rather than an energy source
• Spores accumulate both triggering and non-triggering glucose analogues to similar intracellular concentrations, indicating that transport alone does not determine germination capacity
• Germination requires both continued presence of the trigger molecule and active protein synthesis, suggesting an intracellular signaling mechanism