A proposed mechanism for the germination of microsporidian (Protozoa: Microspora) spores

Abstract

A hypothesis for the mechanism of microsporidian spore germination is presented which is consistent with the experimental evidence available. Based upon concentrations of the disaccharide, trehalose, in germinated and ungerminated spores, stimulation by anions and cations and the high osmotic pressures involved in germinating spores, the following explanation is proposed: monovalent ions diffuse passively into the spores, stimulating changes which cause trehalase to come into contact with trehalose, possibly through an intermediary calcium exchange or release. As trehalose is degraded into higher concentrations of smaller molecules, the osmotic pressure increases until the filament begins its emergence. Once started, expulsion is completed by the osmotic movement of water into the spore, maintaining the pressure as the filament and sporoplasm are forced out. This hypothesis is discussed in light of existing data and hypotheses on microsporidian spore germination and the role of trehalose in the germination of fungal spores. Methods for testing some predictions arising from this hypothesis are suggested.