NUTRITION OF MICRO-ORGANISMS 



Bacteria that grow well without added nicotinic acid presumably 

 synthesise sufficient for their needs. The formation of nicotinic acid 

 on a synthetic medium was in fact demonstrated by P. R. Burkholder 

 and I. McVeigh ^^ for E. coli, B. aerogenes, B. mesentericus and B. 

 vulgatus. 



According to M. R. Bovarnick,^^ the product obtained by heating 

 glutamic acid, methionine or certain other amino acids with asparagine 

 or iso-asparagine at ioo° C. at pH 7, could replace nicotinamide as a 

 growth factor for 5. dysenteriae, S. aureus and L. arabinosus. The 

 culture fluid was found to contain nicotinamide. According to P. 

 Ellinger and M. M. Abdel Kader,^^ however, ornithine was a more 

 effective precursor of nicotinic acid. Using two strains of E. coli, 

 isolated from rat faeces and known to synthesise nicotinamide when 

 grown in an ammonium lactate medium, they showed that the amount 

 of nicotinamide synthesised was increased 4j-fold by ornithine and to 

 the extent of only 50 to 70 % by glutamine and arginine. Ornithine 

 was therefore utilised by E. coli for the biosynthesis of nicotinamide, 

 a conclusion of particular significance in view of the isolation of dinico- 

 tinyl ornithine from chick faeces (page 256). It was suggested that 

 arginine and glutamine, with 8-amino groups, were probably converted 

 into ornithine and thus exhibit a similar, though less marked effect. 



No evidence was obtained to suggest that tryptophan could be 

 converted into ornithine, and E. coli could not convert tryptophan 

 into nicotinamide. It may be, however, that other intestinal organisms 

 can effect the first part of this transformation, for a mixed culture 

 from rats' caecum was able to convert tryptophan into nicotinamide. 

 On the other hand, ingestion of ornithine did not increase the output 

 of N^-methylnicotinamide ; perhaps the amino acid was utilised too 

 rapidly for protein formation. 



The synthesis of nicotinic acid by sulphonamide-resistant and 

 sulphonamide-sensitive strains of E. coli was not diminished by 

 sulphathiazole.^^ 



Nicotinic acid was destroyed during cell proliferation by Pseudo- 

 monas fluorescens ^^ and by a mixed culture isolated from faeces. ^^ 

 Destruction was due to enzymic oxidation, which was inhibited by 

 inhibitors of metal enzjnnes, e.g. sodimn azide, or by surface active 

 agents. ^^ Thus, unless an adequate supply of nicotinic acid is main- 

 tained or an organism is able to synthesise it as rapidly as it is used 

 up, the organism will fail to grow. 



H. Mcllwain ^2 has calculated the rate of production of nicotinic 

 acid and the " turnover number " of enzymes containing it. He 

 estimated that, making allowance for the vitamin that passed into 

 the culture fluid, the five bacteria Aerobacter aerogenes, Serratia mar- 

 cescens, Pseudomonas fluorescens, Proteus vulgaris and Clostridium 



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