SUMMARY: LL100-21 utilized 2-, 3- or 4-cyanopyridine (2-, 3- or 4-pyridine carbonitrile) and the corresponding pyridine carboxamides as sources of nitrogen for growth. Studies with intact bacteria and cell-free extracts indicated that 3-cyanopyridine was hydrolysed directly to nicotinic acid by an inducible 3-cyanopyridinase enzyme (a nitrilase), and that the organism also possessed a separately inducible nicotinamidase. In cultures supplied with 3-cyanopyridine or nicotinamide as the source of nitrogen the compounds were hydrolysed to form ammonia, which was utilized for growth, and nicotinic acid, which was not further metabolized and accumulated in the culture medium. In cultures containing 3-cyanopyridine, which had a bacteriostatic effect, little growth occurred until all the nitrile had been converted to nicotinic acid; the specific activity of 3-cyanopyridinase of the bacteria was highest in the early exponential phase of growth and had disappeared by the stationary phase. Measurements of the abilities to either oxidize or release ammonia from heterocyclic, aromatic and aliphatic nitriles and amides by bacteria grown on the various substrates indicated that benzonitrile acted as both a substrate and an inducer of 3-cyanopyridinase activity, whereas benzamide acted as a substrate and an inducer of nicotinamidase. These enzymes are induced separately from the acetonitrile hydratase/acetamidase enzyme system of this bacterium.


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