The Bacterial Synthesis of Thiamin in Animals

In 1914, Cooper (48) showed that alcoholic extracts of fowl s and rabbit s excreta possessed antineuritic potency. He postulated that although part of the vitamin content of the stools was derived from the unabsorbed residue, a substantial part was probably derived from bacterial synthesis. However, extracts of B, coli failed to exert a measurable antineuritic activity. Guerrant and Butcher (24, 25) later were able to show that the stools of rats on a B-deficient diet contained appreciable thiamin. The vitamin was apparently utilized by the screened animal, inasmuch as its requirement for the vitamin (26, 38) varied inversely with the extent of synthesis. The location of maximum synthesis (39) was found to be the large colon, particularly the cecum. It seemed probable that in cecec-tomized animals, part of the colon may assume the functim of the cecum (38, 40). 

Thiamin synthesis by a wide variety of micro-organisms has been studied,. 

The synthesis of riboflavin, like thiamin, was observed in various animals. In the rat the site of synthesis seems to be the colon (25, 26, 40). When synthesis of riboflavin is increased the requirement of the rat for the vitamin diminishes. In the rumen of sheep (49) there is even greater synthesis. The rumen contents showed a riboflavin value about one hundred times that of the feed used (68, 69). In the cow marked synthesis also takes place (51, 52, 53, 68). The daily output of riboflavin in the milk alone was found to be ten times the intake (68). This impressive amount of synthesis affords adequate explanation for the observation that the riboflavin content of the ration of the cow (70) and goat (71) does not appreciably alter the amount of riboflavin secreted in the milk. Riboflavin synthesis also occurs in the feces of fowl, particularly after passage (72) from the body. 

Synthesis of riboflavin by isolated bacteria has also been studied. It was found to be synthesized by the lactic acid bacillus (73), strains of dysentery bacilli (61) and diphtherial organisms (62), E. coli, B. aerogenes, A. fecalis, B. vulgatus, B. mesentericus, B. vulgaris (60), Pseudomonas fluorescens, Proteus vulgaris, Clostridium butylicum (65). 

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