Dimorphism-associated changes in intracellular pH of Candida albicans.

Intracellular pH (pHi) was monitored during pH-regulated dimorphism of Candida albicans using two different methods: (1) by steady-state distribution of propionic acid and (2) by use of polyene antibiotic, nystatin. There was no significant change in pHi during the first 120 min in either bud- or germ tube-forming populations. However, there was a rapid increase around 135 min which also coincided with the time of evagination. The magnitude of increase in pHi was different in the two populations; being 0.44 and 0.14 pH units in bud- and germ tube-forming populations, respectively. In the two diverging populations, the transient increase in pHi was followed by a rapid drop. The sharp rise in pHi of the population destined to form buds was sensitive to orthovanadate and to the depletion of K+ from the medium while this was not the case with germ tube-forming cells. The results suggest that pHi may play an important role in the phenotypic divergence of C. albicans.