104 BACTERIOLOGICAL CHEMISTRY 



replaced by two hydrogen atoms to give desthiobiotin, 

 CO 



/\ 



/ \ ,. , .... 



NH NH which, very surprisingly, is as active as 



CH CH 



I • I ■ 



CHg CH2.(CH2)4.COOH 



biotin itself. Observable growth of Saccharomyces 

 cerevisiae occurs in the presence of a dilution of 1 in 

 4x10^1. Desthiobiotin will not promote the growth 

 of Lactobacillus casei. Hydrolysis of desthiobiotin by 

 acid or by alkali yields a diaminopelargonic acid, 



CH — CH which on oxidation gives pimelic acid, 



I ! ' 



CH3 CH2.(CH2^4.COOH 



COOH.(CH2)5.COOH. Biotin has been shown to be 

 identical with vitamin H which is protective against "egg 

 white injury," and with " co -enzyme R," which is necessary 

 for the resjDiration of the nitrogen fixing organisms, 

 Ehizobiu7n. The action of biotin is inhibited by avidin, 

 the substance in egg white which is responsible for " egg 

 white injury." Since the activity of desthiobiotin is 

 also inhibited by avidin it seems probable that it is the 

 urea grouping of biotin which combines with avidin. 



0-hetero biotin, the analogue of biotin in which the 

 sulphur atom is replaced by an oxygen atom, has about 

 half the activity of biotin lor L. casei, L. arahinosus and 

 Sacch. cerevisiae. It, also, is inactivated by avidin. 



Added biotin is required for the growth of lacto- 

 bacilli, the propionic acid bacteria, CI. acetobntylicum, 

 CI. butylicum, Staphylococcus (0-005 to 0-01 ju,g./ml.). 

 Brucella and hsemolytic streptococci. At present the 

 mechanism of its activity is obscure. 



GIiitamine.--CH2(CONH2).CH2.CH.NH2.COOH. This 



