Shaily Mahendra University of California, Los Angeles
This project will investigate how microbes can degrade and detoxify hazardous chemicals which have an emerging, yet currently unregulated, presence in water supplies. Bacteria that produce monooxygenase enzymes are uniquely capable of biodegrading a variety of recalcitrant compounds, such as chlorinated solvents, petroleum hydrocarbons, pesticides, and ethers. These enzymes contain transition metals to facilitate transferring electrons in biochemical redox reactions, and their efficiency can vary over orders of magnitude depending upon the availability of specific metals. 1,4-Dioxane, a probable carcinogen, whose biodegradation is mediated by monooxygenases, will be used as a model emerging contaminant in this study. 1,4-Dioxane is a stabilizer of chlorinated solvents, a wetting agent in the processing of textile fibers, and a byproduct in several personal care products. In mixed wastes and contaminated sites, metals such as iron, cobalt, copper, nickel, zinc, and other organics coexist with 1,4-dioxane and will influence the monooxygenase enzymes as well as 1,4-dioxane biodegradation rates. Data collected in this research will demonstrate the effects of metals and geochemical conditions on 1,4-dioxane biodegradation by bacteria growing in liquid cultures as well as biofilms growing on sand or carbon-based surfaces. Novel colorimetric and genetic tools will be designed to rapidly estimate the activities of relevant biodegradative and metal-resistant enzymes under different types of growth and environmental conditions. Changes in composition of microbial communities actively engaged in 1,4-dioxane biodegradation will be assessed by using gene chips and powerful DNA sequencing methods.
Conventional clean-up technologies are expensive, consume resources and energy, or move the pollution from one place to another. Bioremediation could be a technically and financially viable option for removing emerging contaminants from soil, sediments, groundwater, and wastewater. This project will provide critical data on fate and transformations of environmental contaminants that have recently fallen under the scrutiny of regulatory agencies. The results from this study will be leveraged by the PI, in collaboration with environmental engineering professionals, to design bioremediation and monitoring systems for industrial and military waste streams. Research efforts will be coupled with mentoring students of diverse backgrounds at the middle school, high school, undergraduate, and graduate levels. In addition to publications and presentations at scientific meetings, the findings will be integrated with curricula of environmental engineering and microbiology courses.
