Bacterial pathways for degradation of nitroaromatics

Abstract

Covering: up to 2006

The last one hundred years have seen a massive expansion in the chemicals industry; however, with this progress came the concomitant pollution of the environment with a significant range of xenobiotics. Nitroaromatic compounds form one such category of novel environmental contaminants and are produced through a large number of industrial processes, most notably the pesticides, dyes and explosives industries. Whilst singly nitrated aromatic compounds are usually mineralised in the environment, multiply nitrated aromatics, such as the explosive 2,4,6-trinitrotoluene (TNT), are recalcitrant and highly toxic. The predominant route of biological transformation of aromatic compounds is oxidation; however, the presence of three electron-withdrawing nitro-groups around the ring prevents oxidation, rendering such compounds resistant to biodegradation. The subsequent accumulation of these contaminants has stimulated much research leading to the isolation of bacteria that possess, to varying extents, the ability to remediate explosives and other nitroaromatic pollutants. The extreme environments created by these toxic substances accelerate the evolutionary process and examples of bacteria that have conscripted metabolic enzymes for novel remediatory pathways are included. This Highlight ends with a discussion of the future of nitroaromatic bioremediation including engineering plants to express bacterial enzymes for use in bioremediation programs.