NICOTINIC ACID (NIACIN) 



the microbiological assay of nicotinic acid, but many other bacteria 

 also fail to grow in its absence. These include Proteus vulgaris,'^ 

 Pr. morganii, ^ Shigella dysenteriae ^ and S. paradysenteriae. ^°' i^' ^^ 

 Cultures of the dysentery bacteria could be trained to grow without 

 nicotinic acid by repeated transfer into media containing progres- 

 sively smaller amounts ; ^^ the variants so produced, however, grew 

 better in the presence of optimal amounts of nicotinamide. Culture 

 filtrates of the variants stimulated the growth of the parent strain, 

 indicating that nicotinamide, or a substance biologically equivalent to 

 it, must have been synthesised by the variant. Nicotinic acid was 

 also essential for the growth oi Acetohacter suboxydans^>'^^ Staphylococcus 

 aureus, ^^ Streptohacterium plantarum ^^ and Clostridium tetaniP A 

 mutant of Escherichia coli that required nicotinamide was produced by 

 Roepke et al.^^ Nicotinic acid enhanced the growth of Leptospira 

 icterohaemorrhagiae ^^ and of Brucella abortus, but not of Br. melitensis, 

 the growth of which was actually inhibited.^^ 



The cell content of L. arabinosus, which assimilates nicotinic acid 

 during growth, rises to 0'7-5-o m/x mol. per mg. of dry weight. It 

 exists in the cell as cozymase.^^" 



High concentrations of nicotinic acid or nicotinamide, e.g. of the 

 order of lo mg. per ml., were found ^^ to inhibit the growth of a number 

 of representative bacteria in a simple medium ; but in casein hydro- 

 lysate the inhibition was much less marked and was completely 

 nullified by the addition of yeast extract. The phenomenon is 

 believed to be an example of nutritional imbalance. 



Nicotinamide suppressed the spread of tuberculosis in mice, the 

 effect of 0-50 to 075 % in the diet being equivalent to that of i mg. 

 of streptomycin four times daily. ^^^ It is unlikely that the effect is 

 due to a direct antibacterial action of the nicotinamide. 



Nicotinic acid is not an essential growth factor for Bacillus para- 

 typhosum A, but is essential for the fermentation of carbohydrates by 

 this organism ; it must first be converted into cozymase.^^ Some 

 organisms, e.g. Haemophilus parainfluenzae, cannot utilise nicotinic 

 acid or nicotinamide in the absence of D-ribose and adenylic acid, 

 although they grow in presence of the mixture just as well as they do 

 in presence of codehydrogenase I.^^ H. parainfluenzae was able to 

 utilise nicotinamide nucleoside, dihydrocozymase and deamino- 

 cozymase, showing that the reaction it cannot perform is the combina- 

 tion of nicotinamide with ribose. The utilisation of nicotinic acid by 

 many micro-organisms is inapeded by the presence of pyridine-jS-sul- 

 phonic acid or its amide, which appears to interfere with its conversion 

 into cozymase (see page 291). Several species of Pasteurella were 

 stimulated by nicotinamide, but not by nicotinic acid,^* suggesting 

 that these organisms are unable to convert the acid into the amide. 



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