Microbial metabolism of quinoline and related compounds. II. Degradation of quinoline by Pseudomonas fluorescens 3, Pseudomonas putida 86 and Rhodococcus spec. B1.

Quinoline catabolism was investigated with different bacterial strains, able to use quinoline as sole source of carbon, nitrogen and energy. Some degradation products of quinoline were isolated from the culture fluids and identified. With Pseudomonas fluorescens and Pseudomonas putida we found 2-oxo-1,2-dihydroquinoline, 8-hydroxy-2-oxo-1,2-dihydroquinoline, 8-hydroxycoumarin and 2,3-dihydroxyphenylpropionic acid as intermediates. With a Rhodococcus strain 2-oxo-1,2-dihydroquinoline, 6-hydroxy-2-oxo-1,2-dihydroquinoline, a red meta-cleavage product and a blue fluorescent compound were isolated. The red compound was identified as 5-hydroxy-6-(3-carboxy-3-oxopropenyl)-1H-2-pyridone. From this the blue fluorescent azacoumarin 2H-pyrano-2-one-[3,2b]-5H-6-pyridone is formed by chemical decomposition. Therefore it can be considered a by-product of quinoline-degradation in Rhodococcus spec. With the present results two different degradation pathways for quinoline in different microorganisms are proposed.