186 PHYSIOLOGY OF THE FUNGI 



has been reported to depress the growth of several fungi, including 

 Collctotrichum lindemuthianum (Mathur et al., 1950), Rhizopus suinus 

 (fechopfer and Guilloud, 1945), and Fusarium lini (Wirth and Nord, 

 1942). Other cases have been observed in our laboratory. In the case 

 of Rhizopus suinus, the addition of inositol overcame the inhibitory effects 

 of thiamine, and we believe it to be effective with certain other fungi. 

 On the basis of these reports, it would seem unwise to add vitamins 

 indiscriminately to media used for the study of fungi which are self- 

 sufficient for these vitamins. 



VITAMERS 



Certain microorganisms are less specific in their vitamin requirements 

 than are animals, owing apparently to their greater synthetic ability. 

 Some vitamin-deficient fungi may respond well to one of the vitamin 

 moieties, as in the case of thiamine, or to a compound similar to the 

 vitamin. The term vitamer w^as suggested by Burk et al. (1944) to denote 

 a compound having vitamin activity but differing in molecular structure 

 from the true vitamin. Usually the structure of a vitamer is closely 

 related to that of the vitamin. More specifically, these compounds are 

 known as thiamine vitamers, biotin vitamers, etc. In general, a vitamer 

 is active for fewer fungi than is the vitamin. Some vitamers are anti- 

 vitamins. This topic is discussed in Chap. 11. 



UNIDENTIFIED GROWTH FACTORS 



It is quite probable that some fungi wdll be discovered which are defi- 

 cient for vitamins or other growth factors w^hich are at present unknown. 

 Fungi which fail to grow in synthetic media to which all the known growth 

 factors have been added offer a challenge and an opportunity to the 

 investigator. Burkholder and Moyer (1943) reported that Candida 

 albicans 475 and Mycoderma vini 939 did not grow unless liver extract 

 was added to glucose-asparagine medium containing six vitamins. One 

 may speculate that the effect of liver extract was due to some amino acid 

 or to an undetermined growth factor, possibly vitamin B12, which is 

 known to be present in liver. In view of the common experience regard- 

 ing the stimulating effect of natural substances on growth of fungi, it is 

 evident that much more investigation on this phase of nutrition is needed. 



SPECIFIC VITAMINS 



In the first portion of this chapter the general aspects of vitamins and 

 growth factors were considered. Different types of vitamin deficiencies 

 and the methods of detecting deficiencies were discussed. The second 

 portion deals with the specific vitamins, their characteristics and 

 functions. 



