The effect of temperature on the ultrastructure of Histoplasma capsulatum during the mycelium‐yeast transition

Abstract

The ultrastructural morphology of the early phases of mycelium-yeast transition in Histoplasma capsulatum after a temperature shift from 25 degrees C to only 34 degrees C is described. Under this condition of lower temperature oxidative phosphorylation is not completely uncoupled and maximum production of heat shock proteins (hsp) occurs. 24 h after temperature shift more than 90% of the cells still appear vital. Alterations in the organization of the mitochondrial cristae are the only ultrastructural changes observed in these cells. In contrast, 70% of the cells degenerate 24 h after a temperature shift from 25 degrees C to 37 degrees C and in the remaining cells mitochondria are rarely observed. These observations are discussed in relation to the production of hsp, the uncoupling of oxidative phosphorylation and the virulence of different strains of H. capsulatum.

Histoplasma capsulatum Heat-Shock 60 Orchestrates the Adaptation of the Fungus to Temperature Stress

“…This is accompanied by an increase in the number of interactions with proteins involved in protein and carbohydrate metabolism, specifically at the cell wall level. These increased interactions might occur in the stress recovery phase, in response to the uncoupling of oxidative phosphorylation [66] and a decline in intracellular ATP levels [67]. Additionally, it has been shown that respiration is coupled in the yeast phase at 37°C, and this change results in cellular adaptation to higher temperatures [65].…”