Excretion of pyruvate in nickel toxicity in wild type and Ni2+ resistant mutants ofNeurospora crassa

The parent wild strainNeurospora crassa Em 5297a and three Ni²⁺ resistantNeurospora 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 inNeurospora crassa Ni^R1. 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 inNeurospora crassa is a derangement in carbohydrate metabolism at step(s) beyond pyruvate and that this is possibly due to decreased invivo activity of Mg²⁺ dependent processes