Phytoremediation of Explosives using Transgenic Plants

In the past century, several explosive compounds have become the major soil contaminants causing health and economic challenges to the society. In the U.S. alone millions of hectares of land are contaminated by various forms of explosives. The two most dangerous explosives, 2,4,6-trinitrotoluene (TNT) and hexahydro-1,3,5trinitro-1,3,5-triazine (Royal Demolition Explosive; RDX), are major environmental pollutants in the USA and present distinct problems for bioremediation. The U.S. Environmental Protection Agency has classified these explosives as Class 1 carcinogens, which are retained in soil and are refractory to degradation. These explosives also seep into the underground water and may potentially contaminate drinking water. Therefore, understanding the biology behind the metabolism of these explosives by microorganisms and plants is imperative to degrade these pollutants from the contaminated soil. Although the biotransformation of TNT has been studied in many organisms, particularly bacteria, the isolation of microorganisms that can solely utilize TNT for growth has remained elusive. In the recent past, several studies have identified and characterized plant enzymes involved in the reduction, conjugation and sequestration of TNT into plant cell walls [1]. In addition, transfer of bacterial nitro reductase genes to plants has shown significant promises to metabolize TNT into relatively less toxic compounds. The major goal of the scientific community is to identify enzymes that are capable of efficiently degrading TNT and RDX, followed by the introduction of these enzymes in plants (transgenic plants) for efficient phytoremediation [2,3].