38 THE COMPOSITION OF FUNGUS CELLS 



* As per cent of total ash. 



enced, probably indirectly through effects on growth or pH, by the 

 type of nitrogen source (64, 143, 194) and by the concentration of 

 nitrogen (78). A low nitrogen supply may be expected to act directly 

 on phosphorus content by restriction of the synthesis of nucleic acids 

 (63). _ 



It is assumed that only phosphorus, sulfur, and chlorine occur in 

 fungi in organic combination; an attempt to isolate organic com- 

 pounds of magnesium failed (143). Phosphorus is, of course, present 

 in several types of organic molecules: sugar phosphates and adenosine 

 phosphates (22, 92, 113), phosphoproteins (107), nucleic acids (63), 

 and phospholipids (p. 47). None of these has been investigated 

 thoroughly in the fungi. 



The inorganic phosphate of fungal mycelium includes orthophos- 

 phate and inorganic condensed phosphates (151). Pyrophosphate 

 occurs in Aspergillus niger (106), but most attention has been directed 

 to the metaphosphates, polymers of the general formula (NaP0 3 ) n . 

 Volutin, a common visible intracellular inclusion, is probably meta- 

 phosphate (85). Metaphosphates have been found in cells of Asper- 

 gillus niger (96) and, possibly, Neurospora crassa (83). The metaphos- 

 phate of A. niger has a molecular weight of 6000-7000 (86). Fungal 

 enzymes which hydrolyze these condensed inorganic phosphates are 

 considered briefly in Chapter 9. Utilization of the bond energy of 

 these compounds to drive synthetic reactions, although not impossible 

 in principle, has not as yet been demonstrated. 



