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Anaerobic bacteria with an unusual appetite for methyl tert-butyl ether (MTBE)

Jars of samples.
Chart 1.

Methyl tert-butyl ether (MTBE) is an intriguing groundwater pollutant and a synthetic chemical with no natural sources. Furthermore, MTBE contains a tertiary carbon and ether bond, which makes degradation a challenge to microorganisms. MTBE was initially introduced as an octane enhancer in gasoline and later as fuel oxygenate at higher concentrations throughout the 1990s. As a consequence of several decades of extensive use, MTBE has become one of the most frequently detected groundwater contaminants in the United States. MTBE has a very strong turpentine-like taste and smell and can only be tolerated in drinking water at very low levels. Exposure to MTBE is also associated with human and environmental health concerns. MTBE received increasing public attention after it was detected as a persistent and widespread groundwater contaminant and has now been widely banned. Nonetheless, problems with contaminated aquifers and drinking water sources persist.

Chart 2.

The fate of MTBE in the environment is mainly dependent upon natural attenuation processes. Most MTBE-impacted aquifers are depleted in oxygen and the fate of MTBE will thus mainly be dependent upon the activity of anaerobic microorganisms. Our overall hypothesis is that long-term MTBE contamination will enrich for anaerobic microbial communities that are capable of utilizing this compound as a source of carbon and energy. We previously demonstrated that anaerobic MTBE degradation can occur under different anoxic conditions, and may be an important process in anoxic environments. However, we still know little about the bacterial species that can utilize MTBE and the anaerobic biodegradation mechanisms are poorly understood.

Our current works aims to identify novel anaerobic bacteria and their genes responsible for the transformation / degradation of MTBE in contaminated aquifers and sediments in order to develop tools for monitoring natural attenuation and enhancing biodegradation of MTBE in the environment. Specifically, we are: 1) Using stable isotope probing (SIP) and single-cell Raman-spectroscopy to identify microorganisms responsible for anaerobic MTBE-degradation; 2) Characterizing anaerobic MTBE-degrading bacteria active in situ in contaminated aquifers; and 3) Assessing the potential for stimulating anaerobic MTBE degradation at different sites though the addition of appropriate co-substrates and amendments.