VITAMINS 193 



Among the first investigators to test the action of biotin on filamentous 

 fungi were Kogl and Fries (1937), who showed that Nematospora gossypii 

 did not grow in the absence of biotin. As httle as 0.4 ^g of biotin per 

 liter permitted almost as much growth as did ten times that amount. For 

 most filamentous fungi 5 /xg of biotin per liter is adequate. The effects 

 of biotin deficiency on the development of the ascospores of Sordaria 

 fimicola are shown in Fig. G8. 



Some filamentous fungi reported as being partially or totally deficient 

 for biotin, with other deficiencies (if any) given in parentheses, are as 

 follows: Chaetomium convolutum (thiamine), Coemansia interrupta (thia- 

 mine), Diplodia macrospora, Endothia parasitica (thiamine), Hypoxylon 

 pruinatum (thiamine), Lamhertella pruni (thiamine), Melanospora destru- 

 ens (thiamine), Memnoniella echinata, Neurospora spp., Ophioholus 

 graminis (thiamine), 0. oryzinus, Ophiostoma catonianum, Penicillium 

 digitatum (thiamine, pyridoxine, pantothenate), Piricularia oryzae (thia- 

 mine), Pleurage curvicolla (thiamine), Podospora curvula (thiamine), 

 Pseudopeziza ribis, Rosellinia arcuata, Sclerotinia camelliae (thiamine, 

 inositol), Sordaria fimicola, Sporormia intermedia, Stachybotrys atra, 

 Thraustotheca clavata. 



Specificity. The biotin molecule is not separable into moieties as is 

 thiamine. One of the first related compounds to be studied was desthio- 

 biotin. As the name indicates, the molecule no longer contains sulfur. 

 The structure of the desthiobiotin molecule is as follows: 



CO 



/ \ 

 NH NH 



I I 



CH3— CH CH— (CH2)6— COOH 



Desthiobiotin 



The removal of sulfur from the biotin molecule destroyed the tetrahydro- 

 thiophene ring and introduced a methyl group. In addition, the acidic 

 chain of desthiobiotin contains one more methylene group than does that 

 of biotin. Stokes and Gunness (1945) tested the growth of some biotin- 

 deficient microorganisms on desthiobiotin and found that this compound 

 was utilized by Neurospora sitophila and three strains of Saccharomyces 

 cerevisiae, but Rhizobium trifolii 209, Lactobacillus casei, and L. arabinosus 

 17-5 were unable to utilize desthiobiotin. From further experiments it 

 was concluded that the yeast synthesized biotin, or some other compound 

 which replaced it, from desthiobiotin, rather than utilizing desthiobiotin 

 directly. The source of sulfur in the medium was found to influence the 

 amount of desthiobiotin converted into biotin, with methionine and 

 sodium sulfate being better sources than cystine, sulfanilamide, or 

 thiamine thiazole. 



Lilly and Leonian (1944) studied the effect of desthiobiotin on 45 



