Fixation technique to preserve the vacuolation ofPenicillium chrysogenum hyphae

Summary It has been shown that a paraformaldehyde/glutaraldehyde/phosphate buffer saline fixative can be used to preserve vacuolation ofPenicillium chrysogenum hyphae from submerged cultures for later image analysis characterisation. After fixing, the proportion of the hyphase as vacuoles and empty cells (in several samples from different fermentations with different initial percentage vacuolations) did not change significantly over about 70h, and there were only minor changes towards smaller vacuoles in the vacuolation size distributions over the same period. This fixation method will permit the storage of vacuolated hyphae, for later analysis either for physiological studies or for dynamic studies of the links between hyphal vacuolation and fragmentation.