Dibutyryl cyclic AMP-enhanced germ tube formation in exponentially growing Candida albicans cells

Competence in germ tube formation for exponential phase cells of several Candida albicans was low (less than 14%) in 0.1 M phosphate buffer (pH 6.8) containing 1 mM proline. Addition of 5 mM dibutyryl cyclic AMP (cAMP), a lipophilic cAMP analog, to the induction medium increased germ tube formation up to 50%. This enhancement occurred only when the cells were grown in medium lacking glucose or fructose as a carbon source. N-Acetylglucosamine-induced germ tube formation was enhanced by dibutyryl cAMP under similar conditions, but the enhancement was only slight. Cyclic GMP (cGMP) or AMP did not enhance germ tube formation, while dibutyryl cGMP, theophylline, and butyric acid were inhibitory. These results show that dibutyryl cAMP stimulation of the germ tube formation depends on the growth phase and the nutritional status of the cell.