Interrelationships in trace-element metabolism in Aspergillus niger

Abstract

Cobalt, nickel and zinc toxicities have been studied in detail in Aspergillus niger from the point of view of their adverse influence on growth, acid formation and overall glucose utilization. At toxic concentrations, all these parameters were impaired to different degrees at various metal concentrations. The counteracting effect of iron and magnesium when supplemented with the toxic metals has been examined. Either of these metals could overcome growth inhibition completely, iron at concentrations uniformly in the range 160-200 [mu]g. ml of culture medium, and magnesium at concentrations varying markedly with the metal toxicity involved. Only magnesium supplementation permitted normal sporulation concomitantly with growth. Magnesium restored growth, acid formation and glucose utilization to normal levels in all cases except in cobalt toxicity, where it had no influence on acid formation and promoted glucose consumption only to the extent of about 87% of the control. Iron reversed the impaired glucose utilization partially in cobalt toxicity alone. In all toxicities it was ineffective with regard to acid production. The results have been discussed, and it has been suggested that zinc toxicity corresponded to a conditioned magnesium deficiency and that due to cobalt to an iron deficiency.