VITAMINS 203 



quantities of one or more vitamins and are called vitamin-deficient fungi. 

 The deficiency may be single or multiple, complete or partial. Partial 

 deficiency may vary from nearly complete to nearly self-suflficient and 

 is more pronounced during the early stages of growth. 



A single deficiency for thiamine has been more commonly reported 

 among filamentous fungi than any other type. Biotin deficiency is like- 

 wise commonly found, often in combination with thiamine deficiency. 

 Deficiencies for inositol and pyridoxine are less common. Two filamen- 

 tous fungi isolated from nature are reported to be deficient for nicotinic 

 acid. Numerous other deficiencies have been induced in mutants by ir- 

 radiation. Some yeasts show complete or partial multiple deficiencies 

 for three to six vitamins, while relatively few filamentous fungi are 

 deficient for as many as three vitamins. 



Absolute deficiencies are not known to be influenced by the environ- 

 ment, while conditioned deficiencies may be affected either by nutritional 

 factors or by factors of the physical environment. Among these, tem- 

 perature and the composition and pH of the medium seem to be the most 

 important. 



Methods of detecting vitamin deficiencies are exact, and accurate 

 determination depends on the ability or inability of a fungus to grow on 

 a synthetic medium composed of pure chemicals, to which known amounts 

 of the various vitamins to be tested are added. Vegetative growth, 

 measured by dry weight, is apparently the most useful criterion of the 

 utilization of vitamins, although reproduction and other processes are 

 likewise affected. 



Compounds having vitamin activity but differing in molecular struc- 

 ture are called vitamers. In general, only compounds of closely related 

 structure have vitamin activity. 



The inhibitory effects of vitamins in excess quantities are apparently 

 common. They are usually evident by slight reduction in rate or maxi- 

 mum amount of growth and are more common with self-sufficient fungi 

 than with those deficient for the vitamin in question. Thiamine is more 

 commonly reported as a growth depressor than other vitamins. One 

 instance of severe inhibition due to excess inositol and temperatures near 

 maximum for growth is discussed. 



The known effects of vitamins on the growth of fungi emphasize the 

 important fact that growth is a result of a number of interacting factors, 

 among which are the vitamins. A proper balance between the different 

 vitamins and with the other nutritional and environmental factors must 

 exist if maximum rate of growth is to take place. 



REFERENCES 



Ar^a Leao, a. E., and A. Cury: Sobre a exigencia de ^cido nicotlnico observada em 

 cogumelo filamentoso; {Microsporum audouini), O Hospital (Rio de Janiero) 

 35: 347-351, 1949. 



