VITAMINS 



181 



pantothenic acid, nicotinic acid, and biotin. S. ludwigii Y-974 and 

 Kloeckera brevis were totally or partially deficient for six vitamins (thia- 

 mine, biotin, inositol, pyridoxine, nicotinic acid, and pantothenic acid). 

 Growth of all of the 38 yeasts reported by Burkholder (1943) was increased 

 by the addition of liver extract to the medium containing the seven 

 vitamins. 



The preceding discussion of the effects of added vitamins on the growth 

 of fungi has been based on the assumption that near-optimum amounts 

 of the vitamins were present in the media. However, the optimum 



20 28 



Days of incubation 



Fig. 38. The effect of concentration of biotin on the rate and amount of growth ot 

 Sordaria fimicola in 25 ml. liquid glucose-casein hydrolysate medium, initial pH 4.4. 

 Growth in this medium containing biotin but no thiamine is evidence that this fungus 

 can synthesize thiamine under these conditions. (After Lilly and Barnett, Am. Jour. 

 Botany 34: 134, 1947.) 



amount of a vitamin may vary with changes in other conditions and may 

 be different for different fungi. We have found that the following 

 amounts per liter of the four commonly needed vitamins are near optimum 

 for many filamentous fungi: thiamine, 100 Mg; pyridoxine, 100 jug; biotin, 

 5 /ig; inositol, 5 mg. 



The effects of biotin concentration on the growth of Sordaria fimicola 

 are illustrated in Fig. 38, which shows a decided increase in growth rate 

 with greater amounts of biotin. Growth was most rapid in a medium 

 containing 6.4 jug biotin per liter (0.16 /zg per flask), but a steady slow 

 increase in dry weight is evident in as low as 0.1 ^g biotin per Hter. 



Absolute and conditioned deficiencies. According to Robbins and 

 Kavanagh (1942), the deficiency of a fungus for a specific vitamin may be 

 absolute or conditioned. Phycomyces blakesleeanus and Ceratostomella 



