Alishewanella sp. strain KMK6 was isolated from textile dye-contaminated soil. The strain was able to decolorize and degrade different azo dyes and displayed high dye degradation ability and tolerance. The bacterium could completely degrade 2.5 g l(-1) dye, Reactive Blue 59 within 6 h. The induction in the level of cytochrome P-450 and activities of azoreductase and NADH-dichlorophenolindophenol reductase were observed in the cells after dye decolorization indicating the role of these enzymes. The intermediates of Reactive Blue 59 degradation were identified by high-performance liquid chromatography, gas chromatography and mass spectroscopy, and Fourier transform infrared spectroscopy. The ecotoxicity has been evaluated for dye and its metabolites by 3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (a yellow tetrazole) and comet assay, and it revealed that the dye degradation products were nontoxic.