Effect of tunicamycin on germ tube and yeast bud formation in Candida albicans

Tunicamycin is an antimicrobial agent which inhibits the first reaction of the dolichol pathway leading to N-glycosylation of proteins. The effect of tunicamycin on the growth of the dimorphic fungus Candida albicans differed depending on the growth phase of the organism. Addition of tunicamycin to stationary phase yeast cells inhibited the resumption of growth of those cells in either morphology, as cultures failed to initiate either yeast bud or germ tube formation. When tunicamycin was added to growing cells, growth was inhibited but not immediately. When it was added to germ tube cultures, nuclear division and septum formation continued for some time before ceasing. Addition of the drug to exponential phase yeast cultures resulted in an approximately 45% increase in cell number before cell division ceased and yeast accumulated in both budded and unbudded stages of the cell cycle. Accumulation of trichloroacetic acid precipitable radiolabelled protein and nucleic acid continued unchanged for some time following addition of tunicamycin; however, after a while a reduced rate of accumulation was noted.