To create the novel chemical-devouring duo, Daniel van der Lelie of Brookhaven National Laboratory and his colleagues inserted the machinery to break down toluene from one bacterium, Burkholderia cepacia G4, into a second type of bacterium, B. cepacia L.S.2.4, which occurs naturally inside yellow lupine. Toluene is a water-soluble organic compound that is widely used as a solvent and is present in products such as paint thinner, nail polish remover and adhesives. Plants containing the modified B. cepacia that were grown in toluene-seeped soil showed no signs of toxicity, because the bugs protected them. Plants lacking the modified bacteria can also draw toluene out of the ground, but the chemical is later released from the leaves through evaporation. Plants carrying B. cepacia, in contrast, returned far less toluene to the atmosphere.
Depending on the type of bacteria utilized, the approach can clear a variety of pollutants. "Other applications we envisage include the use of engineered endophytic bacteria to degrade pesticide and herbicide residues in crop plants, addressing important food safety related issues," the scientists write. The teams next step is to expand the work to other types of trees--including poplars and willows--to clean up contaminated groundwater.