Rocket Propellants

Over the last two decades a significant part of the Coates Lab research focus has been on the bioremediation and attenuation of a range of toxic legacy compounds from the cold war and ongoing military activities including radioactive metals and rocket propellants.

In 1997, the US EPA identified the rocket propellant perchlorate as a widespread contaminant of drinking water sources across the US.  Perchlorate, primarily sourced from the munitions industry and military activities, is a soluble anion known to affect mammalian thyroid hormone production potentially leading to neuropsychological development deficiencies. Its toxicity predominantly results from structural similarity to iodate, which plays an important regulatory role in hormone production by the thyroid gland.

Because of the potential health complications associated with prolonged exposure, perchlorate was added to the EPA’s Contaminant Candidate List (a list of the 50 most critical contaminants in the U.S.) in 1998 where it has remained.  Its current regulatory recommended maximum concentration limit is 1 part per billion in water sources.

Recent studies have indicated that the true extent of perchlorate environmental contamination has been severally underestimated and the identification of its presence in major vegetable and dairy food products indicates that perchlorate may represent an even greater health threat than was previously considered.  Because of its unique solubility and chemical stability under environmental conditions microbial metabolism has been identified as the most practical means of achieving perchlorate contaminant remediation.  However, fifteen years ago only one organism was described which could metabolize this contaminant.  Since that time the Coates lab has isolated and characterized the majority of the known organisms (over forty) that completely convert this important contaminant into inocuous chloride. 

As part of these studies we demonstrated the environmental ubiquity of this metabolism and identified the dominant species responsible in the environment. Furthermore, we determined the environmental factors controlling the activity of these organisms, and together with other groups identified the basic underlying biochemistry and genetics involved. These early studies formed the basis of all known bioremediation technologies aimed at removing perchlorate contamination from water sources and also allowed us to develop several monitoring tools.

Our recent studies have taken advantage of modern molecular and biochemical approaches to understand the evolution of this metabolism on Earth and expand its application to environmental remediation. To this end we have genome sequenced fifteen model organisms and through comparative genomics we have identified the core genetic systems involved in perchlorate metabolism. We are currently focused on understanding the evolution of these genes and their regulation.