In this issue, Meagher and colleagues show that genetically engineered plants can be used to detoxify a hazardous form of mercury that contaminates wetlands and coastal sediments (see page 213). Certain aquatic bacteria convert ionic mercury to methylmercury, an organic derivative that is more readily absorbed into plankton and the gastrointestinal tracts of fish, leading to accumulation in the food chain. Meagher and colleagues set out to generate plants capable of converting methylmercury to a less hazardous volatile form by expressing two bacterial genes that have evolved in mercury-resistant bacteria. Transgenic Arabidopsis expressing these two genes were able to extract methylmercury from their culture media and convert it sequentially to ionic mercury and then volatile elemental mercury, which the plants then transpired to the atmosphere, where it could be diluted to trace levels.