Azoreductases have been identified in several bacteria, such as Klebsiella pneumoniae RS-13, Pseudomonas luteola, Xenophilus azovorans KF46 (Pointing and Vrijmoed 2000), Rhodococcus (Fu and Viraraghavan 2001), Shigella dysenteriae Type I, Escherichia coli and Clostridium perfringens (Moreira et al. 2000; Bin et al. 2004).