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Microbial Interactions with Emerging Contaminants: 1,4-Dioxane and Nanoparticles

Speaker: Dr. Shaily Mahendra, Department of Civil and Environmental Engineering, Rice UniversityAbstract:
Emerging contaminants are chemicals being increasingly detected in the environment, which are perceived to cause adverse ecological or human health effects, but are not yet regulated. Some examples of materials that have emerged recently are industrial compounds, gasoline additives, pharmaceuticals, and nanomaterials. It is particularly important to evaluate contaminant-microbe interactions because microorganisms can (a) transform contaminants into non-toxic products, (b) act as convenient models for toxicity to higher organisms, and (c) serve as sensitive indicators of potential environmental impacts. 1,4-Dioxane and quantum dots are selected as representative emerging contaminants for this presentation.
1,4-Dioxane, a probable human carcinogen, is typically found as an environmental contaminant in conjunction with groundwater solvent plumes as it is commonly used as a stabilizer for chlorinated solvents. In my research, a variety of bacteria containing specific monooxygenase enzymes were shown to degrade 1,4-dioxane. Quantitative and biochemical data generated in this research will facilitate the development of monitoring tools for this important emerging contaminant in natural and engineered systems. Thus, an outcome of microbial-emerging contaminant interactions may be effective, inexpensive, in situ, natural or enhanced bioremediation.
Quantum dots (QDs) are semiconductor nanocrystals valuable for electronics, solar energy generation, and medical imaging applications. QDs consist of heavy metal core/shell structures coated with organics to make them biocompatible. These coatings can be easily weathered under certain environmental conditions. In contrast to coated QDs, weathered QDs are bactericidal. QD toxicity to bacteria was primarily due to cadmium and selenite ions. Once QDs are released into the environment, water and soil characteristics, such as pH, pE, salinity, and natural organic matter, affect their bioavailability and consequent toxicity. Therefore, a potential consequence of microbial interactions with emerging contaminants may be ecotoxicity.
It is important to recognize emerging contaminants and their impact on public health and the environment. A proactive understanding of their interactions with microorganisms will allow us to use them in a sustainable manner and also develop systems to biologically remediate them.

Location: Kaprielian Hall (KAP) - 209

Audiences: Everyone Is Invited

Contact: Evangeline Reyes