340 



VITAMIN REQUIREMENTS 



32 



Inositol, pig per 25 ml 



64 



Figure 5. The response of an 

 inositolless mutant of Neuro- 

 spora crassa to inositol. From 

 Leonian and Lilly (136), cour- 

 tesy of the West Virginia Uni- 

 versity Agricultural Experiment 

 Station. 



ashbyii (170), but neither phytin nor lipositol is utilizable by an inosi- 

 tolless mutant of Neurospora crassa (9). 



As mentioned earlier, no general function of inositol is known in 

 fungi. Inositol overcomes the inhibition caused by high levels of some 

 other vitamins (238, 253), and has been stated to cause a conidial type 

 of growth in Ophiostoma multiannulatum (72). The response of Scle- 

 rotinia camelliae to inositol is conditioned by temperature (8). 



The insecticide y-hexachlorocyclohexane (gammexane) has been in- 

 vestigated as a possible inhibitory analogue of inositol; it is not, how- 

 ever, structurally an analogue of meso-inositol but of mz/co-inositol 

 (125). Gammexane inhibition of Neurospora crassa appears to be 

 based on two mechanisms: an interference with the metabolism of exog- 

 enous inositol in an inositol-requiring mutant and a second mechanism 

 which is independent of inositol metabolism (93). 



11. PARA-AMINOBENZOIC ACID 



Only one fungus, Blastocladia ramosa, deficient for p-aminobenzoic 

 acid (PABA) is known to occur naturally (39a); a yeast, Rliodotorula 

 aurantiaca, is reported to show an absolute requirement (221), and 

 several bacteria require the compound (323). Mutants of several fila- 

 mentous fungi require PABA (17, 68, 83, 115, 195), so it is presumably 

 a normal metabolite. The deficient mutant of Neurospora crassa grows 

 maximally with PABA at about 5 /xg per liter (281); the requirement is 

 lower at acid pH than at neutral pH, presumably by reason of a faster 

 penetration of the undissociated acid into the cell (325). The require- 

 ment of the N. crassa mutant is highly specific: of closely related com- 

 pounds only 2-fluoro-p-aminobenzoic acid has appreciable activity 

 (323). 



