Halide uptake by the filamentous ascomycete Neocosmospora vasinfecta

Abstract

The uptake of Cl-by the ascomycete Neocosmospora vasinfecta was investigated. Intramycelial concentrations of more than 55 mM (890-fold the external concentration) were reached. Accumulation was as inorganic Cland nystatin induced total loss of mycelial Clwithout extensive protein loss, implying that Clretention was not due to binding to macromolecules. Cltransport was largely unidirectional with efflux being low under all conditions. Uptake was temperature dependent (maximal Arrhenius activation energy of 18.0 kcal/mol) and was severely reduced by KCN, dicyclohexylcarbodiimide, and anaerobiosis. A comparison with the inhibition of oxygen uptake under the same conditions implied that Cltransport was not directly coupled to aerobic electron transport. Cluptake was a saturatable function of the external Clconcentration, and apparent Km values of 6.4 x 10-6 M and 10-1 M were calculated. Of the anions tested, only Br-effectively inhibited Cluptake and I-, NO,-, SO,-2, HCO3-, and H2PO-4 were without effect. Cluptake did not require concomitant cation uptake.

Chloride transport in the vegetative mycelia of filamentous fungus Trichoderma viride

“…The comparison of results of T. viride chloride inward transport with those obtained with Neocosmopora vasinfecta (MILLER and BUDD 1975) show remarkable similarities in the values of K M for the chloride influx and in its inhibition by anions. However, data which could enlighten the character of the driving force for the chloride influx and the chargecompensation properties of the carrier were not obtained in this paper.…”

“…Only limited information of chloride transport is available in fungi. The first description of chloride uptake we are aware of has been described by MILLER and BUDD (1975) in the filamentous ascomycete Neocosmospora vasinfecta more than two decades ago.…”

Influence of exogenous sugars and polyols on C1-influx and efflux by the ascomycete Neocosmospora vasinfecta

“…Such mycelium will be termed preincubated mycelium. During the preincubation period the mycelium develops the capacity to take up C1at a rate higher than that of freshly harvested mycelium (17). For transport studies samples of such preincubated mycelium were washed by filtration and resuspended in the desired solutions.…”

“…The filamentous ascomycete Neocosmospora vasinfecta can accumulate Clto intramycelial concentrations exceeding 55 mM (800-fold the external concentration) by a process requiring the expenditure of metabolic energy (17). Although such extensive uptake of Cl-has not been reported for fungi other than Neocosmospora (see references 3, 21) the ability may in fact be more widespread than previously thought.…”

“…Although Cl-accumulation by Neocosmospora is probably against an electrochemical gradient, with energy being derived from endogenous respiration (17), Cl-uptake is inhibited by the addition of glucose, the usual carbon and energy source for growth, to the external solution (16,17). Not only does exogenously supplied glucose inhibit Cl-influx but it also stimulates Cl-efflux from a preformed Clpool (16).…”