Azo dyes are considered as electron-deficient xenobiotic
compounds because they possess the azo (N]N) and sulfonic
(eSO3
) electron-withdrawing groups, generating electron
deficiency in the molecule and making the compound less
susceptible to oxidative catabolism by bacteria. As a consequence,
azo dyes tend to persist under aerobic environmental
conditions [1].
Some specialized strains of aerobic bacteria have developed
the ability to use azo dyes as sole source of carbon
and nitrogen [2,3]; others only reduce the azo group by special
oxygen-tolerant azo reductases. However, these azo reductases
have a narrow substrate range [4e6]. Recently
Chen et al. [7] have described bacterial strains which display