Spring 2019 – GoMRI Researcher Interview with Dr. Melanie Beazley

(From Spring 2019 Newsletter) Dr. Melanie Beazley from the University of Central Florida’s Department of Chemistry answered a few questions about her RFP-VI project, Biodegradation of “Hidden” High Molecular Weight Polycyclic Aromatic Hydrocarbons: Closing Critical Research Gaps.

1. Please tell us about your RFP-VI project, Biodegradation of “Hidden” High Molecular Weight Polycyclic Aromatic Hydrocarbons: Closing Critical Research What are the goals of the project?

The goals of our GoMRI RFP-VI research project entitled Biodegradation of “Hidden” High Molecular Weight Polycyclic Aromatic Hydrocarbons: Closing Critical Research Gaps are to determine how polycyclic aromatic hydrocarbons (PAHs) with molecular weights greater than ~300 g/mol are degraded by microorganisms, and identify the by- products produced from their breakdown. Very little is known about the environmental occurrence and fate of these large, complex residues of crude oil, which comprise the most toxic, carcinogenic, and mutagenic substances on EPA’s list of priority pollutants. Determining how these toxic “hidden” PAHs behave in our environment is important for our overall understanding of oil spills and their aftereffects.

2. What is your background, and how did you get involved with this kind of work?

My primary background is in geochemistry and microbiology. I have a B.S. in chemistry and followed that with a M.S. in oceanography, which is when my love of studying the chemistry of the ocean began. Subsequent doctoral work in the bioremediation of uranium contamination led to post-doctoral studies in microbiology. Through my studies I have learned that to fully understand our complex and highly dynamic environment, one must consider all the forces that affect that natural system. Chemical, biological, geological, physical, and especially microbiological factors exert controls over the behavior of contaminants such as crude oil, and ultimately, how contamination affects our natural resources as well as human health. Therefore, my research combines geochemical, microbiological, and analytical strategies to understand how our natural systems work.

3. What are some of the most significant or exciting findings so far in your GoMRI-funded research?

We have confirmed in our GoMRI research that large, high molecular weight PAHs including the 5- and 6-ring benzene structures of benzo[a]pyrene (BaP) and the isomers of dibenzopyrene, respectively, are degraded very slowly (on the order of months-to-years) by bacteria. We have determined that a natural consortia of bacteria that we isolated from Deepwater Horizon oil-contaminated sediment were more efficient at degrading BaP than the laboratory strain Mycobacterium vanbaalenii; however, only slightly and still over several months. Analytical separation of these by-products by high performance liquid chromatography (HPLC) allowed for subsequent fraction collection of the individual products, which were further analyzed by laser fluorescence, nuclear magnetic resonance (NMR), and mass spectrometry. We are continuing our consortia culture experiments with the individual isomers of dibenzopyrene as well as conducting sediment microcosms treated with the dibenzopyrenes. Metagenomics analysis by high throughput sequencing of the microcosms will allow us to determine how the overall microbial community of natural Gulf of Mexico marsh sediment changes as a result of exposure to these high molecular weight PAHs. This data will help us to understand the effects of these recalcitrant crude oil by-products that may remain in coastal sediments for years.

4. Why is identifying and analyzing the by-products important? What did the analysis of the individual products reveal?

We know very little about these by-products and suspect they are just as toxic as the parent compounds. Large PAH molecules are not degraded all in one step. They are enzymatically degraded in small increments that produce many different by-products. And as we are discovering, this degradation process occurs so slowly for these complex structures that it is difficult to collect the by-products in appreciable concentrations that can meet the limits of detection of our analytical methods.

5. Can you share a bit more about the culture experiments?

Pure culture experiments, where there is only the bacteria growing in media with the PAH, allows us to determine if and how well the PAHs are degraded in a controlled environment without interferences of other organisms or sediment particles. We then add complexity to the experiments by moving to sediment to determine how the microbial community changes as a result of the PAHs.

6. If funding were not an issue, what would you add to your GoMRI-funded project?

If funding were not an issue, I would expand the time and scope of our project. I would like to run our culture experiments for several years to see if we can achieve complete degradation of these complex structures as well as complete degradation of the by-products all the way to carbon dioxide. These long-term experiments would allow us to determine the complete breakdown mechanism pathways of these PAHs. Additionally, I would like to run a comprehensive transcriptomic and proteomics study of the effects of these PAHs on natural bacterial communities.

[Back to the Spring 2019 Newsletter]