E. L. TATUM 451 



Strains, and conversely growth-factor syntheses by normal strains, are 

 controlled by genes located on the chromosomes in the nucleus of the 

 organism rather than by extra-nuclear factors. It might even be suggested 

 that a microorganism which had developed an extra-nuclear system of 

 control of growth-factor synthesis might not survive since such an 

 extra-nuclear system might be more susceptible to environmental modi- 

 fication and accidental loss or destruction. 



Although strains of fungi, either of natural origin or mutant strains, 

 are known which require almost all of the B-vitamins which are required 

 by bacteria or higher organisms, rather less is known of the exact function 

 of these vitamins in fungi than in some other organisms. Although there is 

 every reason to believe that the B-vitamins have the same coenzyme 

 functions in fungi as they do in other organisms, direct demonstrations 

 of this in the filamentous fungi are available in only a few instances. That 

 thiamin in the form of cocarboxylase is involved in the respiration of 

 fungi is indicated by the accumulation of pyruvic acid in thiamin- 

 deficient cultures of Vhycomyces blahesleeanus (32) as well as by the 

 stimulating effect of thiamin on the respiration of homogenized Sclero- 

 tium delphinii mycelium (61). The situation presumably is similar in 

 Nettrospora since carboxylase has been demonstrated in this organism 

 (83). Although the involvement of vitamin B2 in the glucose oxidase 

 system oi Penicillium has been established (8), and D-amino acid oxidase 

 has been demonstrated in Neurospora (37), the participation of riboflavin 

 in this enzyme in Neurospora has not yet been established. In Neurospora 

 pyridoxal phosphate has been demonstrated to be the coenzyme of the 

 tryptophane synthesizing system (86). Very little evidence is available 

 in regard to /?-aminobenzoic acid, biotin, and pantothenic acid with the 

 exception of an early report by Giese and Tatum (28) that they were 

 involved in respiratory systems in Neurospora. Although biotin has 

 been shown to be involved in sexual reproduction of certain fungi, 

 such as Sordaria fijnicola (3), only two lines of evidence link the action 

 of biotin in fungi with its functions in other organisms. These are reports 

 that biotin may be spared by oleic acid for Neurospora (36), and by 

 aspartic acid for several other fungi (60). 



Investigations with mutant strains of Neurospora may provide a clue 

 to the nutritional function of inositol. The effect of inositol on this 

 organism was early described by Beadle (5). Limiting amounts of this 

 substance have been found to alter profoundly morphogenetic growth 



