COPPER 309 



economic coefficient and on carbon dioxide evolution. The effect of 

 zinc on citric acid formation is, in almost all reported instances, to 

 decrease the per cent conversion of carbohydrate to citrate (35). This 

 zinc effect is not specific; citric acid accumulation is favored by other 

 mineral deficiencies (36). 



2. Lowering of specific enzyme concentrations in cells grown in 

 low-zinc media. Enzymes affected include pyruvic carboxylase (59, 

 242) and ethanol dehydrogenase and the tryptophan-synthesizing en- 

 zyme (156). Diphosphopyridine nucleotidase, on the other hand, is 

 increased by moderate zinc deficiency (156, 157). It should not be 

 assumed, however, that these effects are specific to zinc. 



3. Decrease by zinc of the accumulation of certain antibiotics (141, 

 245). In Aspergillus ochraceus, the specific 6/?-hydroxylation of steroids 

 is much retarded by zinc deficiency (51). 



4. Increase in cytochrome synthesis in Ustilago sphaerogena at high 

 zinc (76), with an accompanying decrease in ferrichrome accumula- 

 tion (158). 



5. Changes in cell composition (127, 189, 214). 



6. Stimulation by zinc of the in vitro formation of vesicles by Puc- 

 cinia coronata (218). 



7. A shift in the proportions of related ring compounds produced 

 by Penicillium urticae (52). 



8. Effects of zinc supply on sporulation, reviewed by Foster (57). 



Zinc is known to activate a few enzymes specifically (126) and 

 others non-specifically (207); ethanol dehydrogenase and glutamic de- 

 hydrogenase are zinc proteins (249, 250). The diverse effects of zinc 

 on metabolism suggest in addition that it is concerned with the syn- 

 thesis of enzyme proteins; this hypothesis applies especially to the 

 second, third, fourth, and seventh effects just listed. 



7. COPPER 



Copper is required by fungi for normal growth and sporulation at 

 about 0.01-0.1 ppm (36, 37, 100, 241). Higher concentrations are of 

 course toxic, although two fungi make visible growth even in a satu- 

 rated solution of copper sulfate (226). The uptake of copper is some- 

 what greater at moderate pH than at low pH (215). 



Perhaps the most striking physiological effect of copper deficiency is 

 the reduction in pigmentation of the colored spores of Aspergillus spp. 

 (26, 102, 142, 150) and Trichoderma viride (27). Although other metal 



