This study provides a first attempt from a growth-association perspective to put forward, in general terms and explanations, plausible selection on optimal decolorizer to a model diazo dye Evercion Red H-E7B (C.I. reactive red 141; RR141). According to Gaden's classification scheme of fermentation, the bioactivity series of three decolorizers used in this study is Escherichia coli UVT1 > Pseudomonas luteola >> Escherichia coli UV68. The relative toxicity among the parent dye RR141 and its derived intermediates is likely the leading cause of low biodecolorization performance. For P. luteola, the oxygen-repression characteristics on decolorization of RR141 is due to the obligatory requirement of oxygen-sensitive azoreductase expression to precede non-growth-associated decolorization. In contrast, as E. coli UVT1 might contain a more diverse decolorization capability besides azoreductase, it proceeded color removal in relatively higher rates than P. luteola. Compared to other strains, the highest color removal performance of UVT1 might be due to negligible toxicity of intermediary products and dye RR141. However, perhaps owing to induced mutation occurred on "DNA domains" originally dealing with bacterial tolerance to azo dyes, decolorization capability of UV68 to RR141 was found to be completely repressed.