Ultrastructure of Synchytrium endobioticum resting spores and enhancement of germination using snails

Living resting spores of Synchytrium endobioticum empty their contents into germination vesicles. After resting spores were fed to water snails, germination (production of vesicles) rate increased. Transmission electron microscopy revealed that the wall was composed of an exospore, likely derived from the host potato cell; a mesospore; and an endospore composed of the vesicle wall and the sporangial wall. Scanning electron microscopy showed that passage through snails eroded the exospore. This was confirmed by examination of freeze fractured resting spores. We conclude that germination (vesicle production) followed loss of impermeability.