The development of an increased rate of Cl- uptake in the ascomycete Neocosmospora vasinfecta.

Freshly harvested mycelium of the filamentous ascomycete Neocosmospora vasinfecta accumulated C1- against a concentration gradient by a process probably requiring the expenditure of metabolic energy. When mycelium, washed free of growth medium, was incubated in deionized water or tris (hydroxymethyl) aminomethane sulfate at pH 7.5 for 4 h and then transferred to K36C1 solutions, the C1- uptake rate was, on the average, 3.77 +/- 0.26 (+/-SE, N = 20) times the uptake rate exhibited by freshly harvested mycelium. This development of an increased rate of Cl- uptake could be blocked by the presence of an inhibitor of ribonucleic acid synthesis (azaguanine) or of protein synthesis (cycloheximide, fluorophenylalanine, or puromycin). The combined presence of glucose and a potassium salt in the preincubation solution virtually arrested the development of enhanced Cl- uptake. The rate of Cl- uptake by freshly harvested mycelium did not vary greatly with the age of the culture on harvest but the ability to develop an increased rate declined with age. The fact that it is possible to obtain mycelium possessing widely different capacities for Cl- uptake should assist in biochemical characterization of the Cl- uptake system.