Temperature- and cyclic nucleotide-induced phase transitions of Histoplasma capsulatum

Abstract

The transition from yeast to mycelia of H. capsulatum could be accomplished by shifting the temperature of incubation from 37 to 25°C. It was accompanied by many changes in cellular metabolism, including changes in respiration, intracellular cyclic adenosine 3',5'-monophosphate (cAMP) levels, and activities of two enzymes specific for the yeast phase, cystine reductase (EC 1.6.4.1) and cysteine oxidase (EC 1.13.11.20). Even at 37°C, the yeast to mycelial transition could be induced by cAMP and agents which raise the intracellular levels of cAMP (theophylline, acetylsalicylic acid, prostaglandin E 1, and nerve growth factor). During this morphogenesis the same pattern of changes occurred as in the temperature-induced transition. Therefore, these changes were not simply dependent on a shift in temperatures, but rather were part of the process of the phase transition.