VI. HIOCKNKSIS 587 



iliai ilic.-^c liidtiii niialoos arc utili/.cd (lii<'cll\- without pi'ior (•(nixcrsioii to 

 1 lie \itainiii. 



VI. Biogenesis 



I'Aii. (;y()U(;v 



The i)es( sources of hiotiu are yeast/- lower fuuoi including Aspergilli 

 and P( nicillia,^ and bacteria.^ It may be assumed that animals derive the 

 biotin they require, at least in pnvt, from such micr()biol()j2;ical synthesis 

 of biotin. The amount of biotin i-eleased by bacteria into the culture me- 

 dium may be several times that present in bacterial cells.'' It is not due 

 to the autolysis of dead cells, and it appears to be the vital function of the 

 lixinti microorganisms. 



It has been shown that bacteria in the rumen of cattle are biotin pro- 

 ducers.^ ' The fact that rats and man on a diet low in biotin excrete much 

 more l)i()tiii than they do when biotin is supplied in the diet is also explained 

 l)v the synthesis of V)iotin inside the body, through activity of the intestinal 

 bacteria. In man the urinary output of biotin is roughly proportional to 

 the intake, whereas the fecal excretion may greatly exceed the intake.**"^'- 

 In rats receiving raw egg white in their diet the amount of biotin excreted 

 in the urine and in the feces far exceeds that in the diet. This excess biotin 

 must hsive originated chiefly from the non-dietary source of intestinal syn- 

 thesis.^'^ 



' R. .1. WilliaMLs. R. E. Eakin, and K. K. Snoll. ./, Am. (Item. Soc. 62, 1204 (1940). 



- b. II. Looiiian and V. G. Lilly, Science 95, 6.58 (1!)42). 



•■' B. (". J. (;. Knifrlit. Vitamins anil Hormones 3, 105 (1945). 



' \V. II. Peterson and M. S. Peterson, Bacieriol. Rcrs. S, 19 (1945). 



* R. C. Thompson. Cnir. Texas Pithl. 4237, 87 (1942.). 



'■ I.. W. M(i:irov ;ind T. 11. Jukes, Proc. Soc. Exptl. Biol. Med. 45, 296 (1940). 



■ .M. I. Wctiner. .V. X. lUnAh, C. A. lOlvehjem, and E. B. Hart. Proc. Soc. Exptl. 

 Biol. Meil. 45, 7()9 (1940). 



" T. W. Oppel, Am. .J. Med. Sci . 204, 886 (1942). 



U. Gardner. H. T. Parsons, and W. H. Peterson. Arch. Biochem. 8, ;5;}9 (1945). 

 '« J. Gardner. II. T. Par.sons, and W. H. Peterson, Am. ./. Med. Sci. 211, 198 (1946). 

 " C. W. Denko, W. E. Grundy, J. W. Porter, G. H. Berrvman. T. E. Friedemann. 



and J. B. Vounians, Arch. Biochem. 10, 33 (1946). 

 '2 C. W. Denko, W. E. Grundy, X. C. Wheller, C. R. Ileiiderson, G. II. Bcirynian, 



T. E. Friedemann, and J. B. Youmans, Arch. Biochem. 11, 109 (1946). 

 '•^ M. .\. McGregor. II. R. Parsons, and W. H. Peterson. ./. Xntrition 33, 517 (1947). 



