InNeurospora crassa,0.44 mM Be²⁺ caused half-maximal inhibition of growth and this inhibition could be fully counteracted by the addition of 2.5 mM Ca²⁺ to the medium. Mn²⁺ and Mg²⁺ were less effective in reversing the growth inhibition caused by Be²⁺ and the order of effectiveness was Ca²⁺ > Mn2+ > Mg²⁺. Fe3+ and Zn²⁺ were ineffective in reversing Be²⁺ toxicity.

Pyruvate, malate and succinate also reversed the growth inhibition caused by Be²⁺ inN. crassa. Pyruvate restored growth by a mechanism not involving control of Be²⁺ accumulation in the mould. The rate of utilisation of glucose by the mycelia grown in the presence of Be²⁺ was reduced, while that of pyruvate was not affected. The results indicate that the primary metabolic lesion in Be²⁺ toxicity inN. crassa is probably a block at some step(s) in the glycolytic sequence.

Among several metal ions tested, Cu²⁺ was unique in slowing down methylene blue sensitized photodynamic breakdown of some nucleic acid bases and nucleosides. The t_1/2 values were increased in the case of xanthine and uric acid by Cu²⁺, but without any alteration in the nature or amounts of photoproducts formed. Xanthine was degraded quantitatively to allantoin and urea.

The breakdown of the sugar moiety of nucleosides was more drastically retarded than that of the purine ring. The decomposition rate and its magnitude was dependent on the concentration of Cu²⁺ as well as the nucleoside. The most profound increase in t_1/2 values was found with xanthosine—7 min for the purine ring and 65 min for the ribose moiety, at 0.6 mM Cu²⁺ Hg²⁺ in the case of xanthine, and some paramagnetic metal ions in the case of the nucleosides, slowed down the photobreakdown to a small extent; however, differential effects were not observed unlike with Cu²⁺. None of the other metal ions tested significantly influenced the process.