VI. BIOGENESIS 447 



the yield of the \-itamiii. Tlie most striking discox'ery was the effect of the 

 addition of cobalt to the fermentation medium in the biosynthesis of 

 LLD-active substances l\v Strcplomyces griseus and a large number of other 

 vitamin Bi2-producing microorganisms.^ Addition of one or two parts per 

 million of cobalt ion produced optimum production of LLD-active sub- 

 stances. The stimulation due to added cobalt ion has been put to practical 

 use in the formation of vitamin B12 containing cobalt 60.- By addition of 

 cobalt 60 as the nitrate of specific activity 1.800 nc per milligram to the 

 nutrient medium, it was possible to obtain vitamin B12 with a specific 

 activity of c^ 67 nc. per milligram.- 



Addition of 1 ,2-dimethyl-4,5-diaminobenzene to bacterial cultures of 

 Bacillus megatherium stimulated the production of vitamin B12 and also 

 riboflavin.^ These results are not surprising; in both vitamins, the diamine 

 may be considered as a degradation product and a precursor.'' • ^ Addition 

 of 1 ,2-dichloro-4,5-diaminobenzene to similar bacterial cultures brought 

 about an inhibition in the production of vitamin B12 and riboflavin when 

 the dichloride was present in an insufficient quantity to inhibit growth of 

 the organism.^ 



The activity of choline chloride has been tested on fourteen strains of 

 microorganisms isolated from poultry house litter. The vitamin B12 produc- 

 tion of twelve strains was reduced and that of two strains was improved 

 by addition of choline chloride to the medium.^ 



Investigations of the vitamin B12 content of the intestinal tract of various 

 animals and man has given some evidence on the biogenesis of the vitamin. 

 Sheep iiimen has l:)een found to be a fairly rich source of vitamin B^.^ 

 About one-half of the colmlt ion fed to sheep was excreted in organically 

 bound form in the feces. Biological assay of the butanol extract of feces 

 indicated the presence of large amounts of \dtamin B12.* Only two types of 

 bacteria. Bacillus subtilis and a corynebacterium, were found in fresh pig 

 stomach mucosa and in a commercial preparation of this tissue.^ These 

 produce \'itamin B12 and control bacterial growth in the mucosa. Vitamin 

 B12 has been found at \'arious levels in the alimentary canal of man and 



1 D. Hendlin and M. L. Ruger, Sciejice 111, 541 (1950). 



2 C. Rosenblum and D. T. Woodbury, Science 113, 215 (1951); L. Chaiet, C. Rosen- 

 blum, and D. T. Woodbury, ibid. Ill, 601 (1950). 



' D. W. Woolley, Proc. Soc. Exptl. Biol. Med. 75, 745 (1950). 



* N. G. Rrink and K. Folkers, J. Am. Chem. Soc. 71, 2951 (1949). 



6 N. G. Brink and K. Folkers, J. Am. Chem. Soc. 72, 4442 (1950). 



6 E. R. Ilalbrook, F. Cords, A. R. Winter, and T. S. Sutton, J. Nutrition 41, 555 



(1950). 

 ' V. J. Lewis, U. D. Register, H. T. Thompson, and C. A. Klvehjem, Proc. Soc. 



Exptl. Biol. Med. 72, 479 (1949). 

 8 P. H. Abelson and H. H. Darby, Science 110, 566 (1949). 



3 B. Noer, Lancet 259, 706 (1950). 



