Isolation, characterization, and substrate utilization of a quinoline-degrading bacterium

A Gram (+) rod-shaped organism identified as a Rhodococcus sp. capable of growth utilizing quinoline as the dominant carbon, energy, and nitrogen source was isolated from soil. The isolate, designated as Rhodococcus sp. Q1 was also capable of growth on 2-hydroxyquinoline, pyridine, 2,3-dimethylpyridine, catechol, benzoate, and protocatechuic acid, suggesting a diverse capacity for aromatic ring degradation. Concentrations of quinoline in excess of 3.88 mM were toxic. Although ring nitrogen was released into the growth medium as ammonium, quinoline degradation was not limited by the availability of inorganic N. A degradation product was isolated and identified as 2-hydroxyquinoline on the basis of ultraviolet, fluorescence emission, and mass spectroscopy. When grown on quinoline or 2-hydroxyquinoline, this bacterium produced pigmented compounds.