Cultures of Mycobacterium vanbaalenii strain PYR-1 in a liquid medium were exposed to the toxic environmental contaminant acridine (260 microM). After incubation for 7 d, the cultures were extracted with ethyl acetate. Metabolites were purified using high-performance liquid chromatography and analyzed by mass spectrometry and 1H nuclear magnetic resonance spectroscopy. Four metabolites, 9,10-dihydroacridine, 4-hydroxyacridine, acridine cis-1 ,2-dihydrodiol, and acridin-9(10H)-one, were identified.