310 INORGANIC NUTRITION A N D M E T A B O L I S M 



deficiencies also affect spore pigmentation (58), copper is probably the 

 most important, at least for the dark spore pigments. 



It has been mentioned earlier (Chapter 6) that copper may play a 

 role in chlorine metabolism of fungi. The possibility that, as in ani- 

 mals (134), copper is essential for normal iron metabolism has not been 

 explored. 



8. MANGANESE 



The essentiality of manganese in small amounts, about 0.005-0.01 

 ppm, has been demonstrated for a number of fungi (23, 36, 53, 57, 86, 

 137, 190, 199, 227, 241); we may assume that fungi in general require it, 

 although the effects of deficiency are not apparent for all. The re- 

 quirement is more easily shown at low pH than at high (121). 



Manganese deficiency has several physiological effects (57, 183), in- 

 cluding a pronounced decrease in sporulation. The frequent role of 

 the metal in activation of enzymes, especially those of the citric acid 

 cycle (136), suggests a role for it in metabolism at this point; manga- 

 nese concentration also affects the concentration of other enzymes in 

 the cell (86). 



The biological oxidation of manganese in soil can be demonstrated 

 perhaps best in soil percolation experiments (129). It is probable that 

 fungi as well as other organisms carry out this reaction; the limited 

 evidence is reviewed by Mulder and Gerretsen (153) and by Starkey 

 (225). 



9. MOLYBDENUM 



The essentiality of molybdenum for Aspergillus niger was discovered 

 by Steinberg (229). The requirement is small — estimates range from 

 0.1 parts per billon (152, 168) to 10 ppb (241) — and A. niger responds 

 to as little as 0.02 ppb (152). Vanadium does not replace molybdenum 

 (168). 



It has been observed repeatedly that the molybdenum requirement 

 of both Aspergillus niger and Neurospora crassa is higher if nitrate is 

 used as the source of nitrogen than if ammonium nitrogen is provided 

 (152, 170, 230). The explanation for this phenomenon is the first un- 

 equivocal demonstration of a specific enzymatic basis for a deficiency 

 symptom in fungi. Molybdenum participates as electron carrier in the 

 reduction of nitrate by enzymes of Neurospora crassa, Escherichia coli, 

 and soybean; the evidence for this conclusion is reviewed by Nason 



