Chapter VA 



BIOGENESIS OF THE B VITAMINS 



Some discussion of the biogenesis of the B vitamins in general will be 

 included below in the section on thiamine. Otherwise we shall treat each 

 member of the group separately and endeavor to present in the respective 

 sections the present status of knowledge with regard to where they origi- 

 nate in nature and in some cases the probable raw materials. Certain 

 details regarding the biosynthesis of the B vitamins which hinge on plant 

 and animal metabolism, intestinal bacterial synthesis in relation to sup- 

 plying the requirements of higher organisms, and upon inhibition studies 

 will be presented in later chapters. 



Thiamine 



Several positive answers can be given to the question as to where 

 thiamine is produced in nature. First, we may say that it is produced 

 by numerous bacteria, presumably all those which can grow on simple 

 media, and by many which require other vitamins. Definitive information 

 on this matter is fragmentary. Peterson and Peterson, 1 in a list of 136 

 organisms which have "growth factor" requirements, indicated 8 which 

 have been found to synthesize thiamine, 12 others which do not require 

 thiamine (and presumably synthesize it), 36 which require or at least are 

 stimulated by it, and 80 for which no information is available. In another 

 table, "23 organisms reported to synthesize thiamine were listed (p. 299). 

 Of the bacteria which are stimulated by thiamine, probably a good many 

 actually synthesize it, as has been demonstrated with certain yeasts. 2 

 Knight 3 has listed 10 bacteria which are capable of synthesizing thiamine, 

 and Najjar and Barrett 4 list 18 such bacteria. The latter list, however, 

 includes organisms for which synthetic ability was indicated before thi- 

 amine and other members of the B family of vitamins were clearly dif- 

 ferentiated. Thompson 5 studied 5 bacteria chosen because of their diverse 

 characteristics, all of which, however, were capable of being grown on 

 relatively simple media, and found that they all produced substantial 

 amounts of thiamine. 



The extent to which thiamine synthesis by bacteria in the soil and in 

 the digestive tracts of animals, particularly in the rumen of cattle, etc., 

 figures in the economy of nature is difficult to assess (see Chapter II C), 



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