Biosynthesis of Nicotinic Acid by Mycobacterium Tuberculosis.

Although the bacterium Xanthomonas pruni utilizes the classic "tryptophan pathway" to synthesize nicotinic acid (Wilson and Henderson, J. Bacteriol. 85:221, 1963), evidence is accumulating that most bacteria do not exhibit a tryptophan-nicotinic acid relationship. The absence of such a relationship in Escherichia coli and Bacillus subtilis was reported by Yanofsky (J. Bacteriol. 68:577, 1954). Ortega and Brown (J. Biol. Chem. 235:2939, 1960) showed that E. coli synthesizes nicotinic acid from a four-carbon dicarboxylic acid and glycerol or some other closely related three-carbon compound. Nutritional studies by del Rio-Estrada and Patino (J. Bacteriol. 84:871, 1962) revealed that glycerol did not stimulate nicotinic acid formation in llycobacterium tuberculosis, and also that C14 from glycerol-2-C'4 was not incorporated into the vitamin. In preliminary nutritional experiments conducted in our laboratory (Moat and Albertson, Federation Proc. 23:528, 1964), it was determined that (i) tryptophan is not utilized by tubercle bacilli for the synthesis of nicotinic acid, (ii) glycerol, as carbon source, effected maximal synthesis of nicotinic acid, and (iii) aspartic acid and glutamic acid enhanced nicotinic acid production. When employed as the sole nitrogen source, aspartic acid and glutamic acid stimulated, respectively, 10.8 and 5.6 ,ug of nicotinic acid per mg (dry weight) of tubercle bacilli as compared with 1.3 ,ug/mg with NH4+ as sole nitrogen source. To determine whether these compounds were incorlporated into nicotinic acid, C'4-labeled glycerol, and aspartate and glutamate labeled in various positions, were incorporated into KonnoSauton media inoculated with tubercle bacilli; the culture was then incubated for 10 days at 37 C. The vitamin was isolated as nicotinic acid picrate and analyzed for C'4 by the technique described by Ortega and Brown (J. Biol. Chem. 235:2939, 1960). To demonstrate further the position of the C14 label, the labeled nicotinic acid