The xenobiotic nature of these compounds and their poor aqueous solubility may help explain why, to date, they have accumulated in the environment. However, within the last decade, after considerable exposure, bacteria are now being isolated from contaminated environments that are capable of mineralizing some of these explosives. For example, a TNT degrading Pseudomonas sp. has been isolated from contaminated water samples from a nitrobenzene production site (Parales 2000). Examination of the gene clusters associated with the nitroarene degradation pathway of this bacterium indicates that the evolution of the pathways is a recent event. This is suggested by the fact that the pathway is not optimized, there are vestigial genes, a lack of co-ordinated regulation, and long acclimatization times (Parales 2000).
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