ABSTRACT
The parent wild strain Neurospora crassa Em 5297a and three Ni2+ resistant Neurospora crassa mutants have been shown to excrete pyruvate into the culture medium in Ni2+ and Co2 + toxicities. Ni2+ has a more pronounced effect in this regard. The excretion is progressive with growth inhibition and is abolished by Mg2+ in all strains and by Fe3+ partially in the Em strain but not in Neurospora crassa NiR1. Pyruvate, citrate and malate supplementation reverse growth inhibition caused by excess Ni2+, but with concomitant suppression of Ni2+ accumulation. It is suggested that one of the features of Ni2+ toxicity in Neurospora crassa is a derangement in carbohydrate metabolism at step(s) beyond pyruvate and that this is possibly due to decreased in vivo activity of Mg2+ dependent processes.