Researchers from the Department of Biochemistry and Department of Chemistry at the University of Wisconsin – Madison recently published a paper in the journal Nature that claims to have solved the structure of a microbial enzyme that attacks toluene, a major subsurface contaminant.

With the discovery of the enzyme structure, the researchers believe that they have an important tool in improving the microbial reactions that destroy organic contaminants in the soil and groundwater.  The work is also valuable in that it provides a glimpse of the mechanics of a process that could be harnessed to help clean up oil spills.

“In this research, we are trying to understand how nature uses iron atoms, electrons, and oxygen gas from the air to selectively oxidize chemicals,” says biochemistry Professor and Chair Brian Fox.  “This reaction is the first step in a process where the carbon atoms in toluene, called an aromatic ring, are prepared for consumption by bacteria.”

This reaction plays out at the atomic level, in a game of electron and atom transfer.  The active site of the large enzyme contains two iron atoms that also store up to two electrons.  These react with oxygen gas to combine and “attack” the aromatic ring of toluene, with electrons being exchanged along the way.  Ultimately, an oxygen atom is added to the toluene ring, opening the door for other reactions used by the bacteria to consume toluene.

When bacteria carry out this transformation of toluene, they start a process that rapidly removes it from the environment.  In this way, bacterial bioremediation is able to remove harmful substances from the environment, something scientists are already taking advantage of to help ecosystems recover from chemical catastrophes like oil spills.