Germination of Rhizopus oligosporus sporangiospores

Abstract

The morphology of Rhizopus oligosporus (NRRL 2710) sporangiospores and their physiological requirements for germination were studied. Germination proceeded in two separable phases: phase I (swelling) and phase II (germ tube protrusion). The optimal conditions for germination were 42°C and pH 4.0. Sporangiospores contained insufficient endogenous carbon for swelling or germination to occur in distilled water. Initial swelling during phase I occurred only in the presence of a suitable carbohydrate. Subsequent production of germ tubes during phase II required exogenous sources of both carbon and nitrogen. Spores germinated most rapidly in mixtures of amino acids; L-proline and L-alanine were the most effective. These amino acids, at concentrations as low as 10-6 M, supported germination when combined with glucose and McIlvaine (citric acid-phosphate) buffer. D-glucose, D-xylose, and D-mannose were the most effective carbohydrate tested for promotion of germination.