Bacterial pathways for degradation of nitroaromatics

Abstract

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.

Nitroaromatic Compounds, from Synthesis to Biodegradation

“…Over the last several years, numerous review articles have specifically addressed the toxicity and mutagenicity of nitroaromatic compounds (117,140,152,162), the biosynthesis of nitro compounds (205), and the biodegradation of nitroaromatic compounds (132,135,180,181,188). Here we present an integrated review of the chemical and biological syntheses of nitroaromatic compounds and our current understanding of bacterial degradation of these toxic and recalcitrant chemicals.…”

Microbial Degradation of 2,4,6-Trinitrotoluene In Vitro and in Natural Environments

“…Besides the two major enzyme classes, an only iron hydrogenase from Clostridium acetobutylicum has been found capable of reducing TNT to its dihydroxylaminoderivate in a hydrogen depending manner (Symons and Bruce 2006).…”

“…In USA, 15 million acres at over 2000 sites are suspected or known to be contaminated with military munitions (Montgomery et al 2011). At some munitions manufacturing and processing sites, the contamination can be as high as 200 g TNT per 1 kg of soil (Symons and Bruce 2006).…”

Synthesis and evaluation of halogenated nitrophenoxazinones as nitroreductase substrates for the detection of pathogenic bacteria

“…[1][2][3][4] For example, the reduction of a nitroaromatic prodrug by a bacterial nitroreductase is central to the GDEPT anticancer therapeutic approach, 5,6 for which the mechanism of the Escherichia coli nitroreductase activation has been elucidated. 7 Nitroreductase enzymes have been subdivided into two different classes, 8,9 namely type I and type II nitroreductases, based on their relative sensitivity to oxygen.…”