Water as a substrate for the development of Paracoccidiodes brasiliensis mycelial form

Two isolates of P. brasiliensis in the mycelial form were studied for their capacity to survive and grow in sterile distilled water (SDW). Inoculum for the experiments consisted of a spectrophotometrically-standardized suspension of washed and homogenized mycelial fragments; these had been obtained from 2-week old cultures grown in a synthetic medium (SM). Series of tubes with SDW and SM were incubated with the above suspension and kept stationary for 6 months at either 4 degrees C or room temperature (RT). Growth was measured by dry weight (DW) and turbidity (OD) determinations; additionally, CFU and ultrastructural appearance by transmission electron microscope (TEM) were assessed for one of the isolates. In general, cultures in SM at RT, grew exponentially after 2 weeks, becoming stationary for 7 weeks and then, declining abruptly. In SDW, fungal development was slow for 5 months when an increase in mass was recorded. When incubated at 4 degrees C, both SDW and SM cultures required longer time to develop but mass also increased. Morphologically, mycelial elements in SDW at RT exhibited increased lipid vacuoles and glycogen deposits but were otherwise normal up to 6 weeks when they presented the inter-hyphae-hyphae phenomenum. In SDW P. brasiliensis appears to utilize debris from its degenerated fungal partners to continue growing.