Discipline: Biological Sciences
Timothy Egbo - Alabama State University
Co-Author(s): B. K. Robertson, Alabama State University, Montgomery, AL
Y-12 National Security Complex around the Oak Ridge Reservation has been identified by the US Environmental Protection Agency (EPA) to have heavily contaminated the upper and lower East Fork Poplar Creek (EFPC) ecosystem with mercury (Hg) through transportation from the source areas via atmospheric deposition, sediment transport, surface water runoff, and groundwater transport contaminating the upper and lower EFPC ecosystem. Hg contamination within the Oak Ridge Reservation has been an ongoing research. The use of sorbents has been proposed as a cleanup strategy; understanding the biological factors that might influence the efficiency of the sorbents or clean up strategy is very essential. For example, bacteria are capable of forming biofilms on surface of sorbents. On the other hand, organism like Serratia marcescens has been identified in recent studies to have anti-biofilm properties. The goal of this study was to use microbe (S. marcescens) isolated from site where Hg is not more than 54.5 ug/g of total Hg (HgT) dry weight. Bank soils contaminated with Hg from EFPC was collected from two sampling sites with soil profiles based on soil color. The samples were collected from two distinct soil layers, the top lighted-colored soil labeled SB 14-8 downstream of the creek, the bottom dark colored soil upstream of the creek labeled SB 5-8 and uncontaminated soil from the Hinds Creek area. Pure cultures were obtained from soil sample SB 14-8 using broad-spectrum nutrient broth, and natural medium formulated using extracts from the different soil samples. S. marcescens was allowed to grow to O.D600 0.5 and then the soil was added to the culture. After 24, 48 and 72 hrs, the cultures were diluted serially and plated for viability count. In addition, culture of S. marcescens in the presence of sorbent Organoclay™ and soil was allowed to mix on a shaker for 48 hrs at 25OC after allowing the soil to stand in diH2O for 14 days. Organoclay™ was added to determine the amount of Hg that can be absorbed in the presence or absence of microorganism. HgT concentrations were determined using cold vapor atomic fluorescence in accordance with EPA method 1631. Our results showed that S. marcescens showed high reduction of Hg in solution compared to the sorbent; nonetheless, this increase in reduction was found to be more significant within the SB 14-8. Our results did not show any significant influence of S. marcescens on the sorbents compared to S. marcescens alone. Its role or influence in reducing HgT in contaminated soils in the presence of sorbents and other microbes are currently being evaluated in our lab. Future study will further examine how S. marcescens can interfere with possible biofilms that might accumulate within the sorbent.ERN_17_TEgbo.docx
Funder Acknowledgement(s): National Science Foundation's Alliances for Graduate Education and the Professoriate (AGEP) Program, Grant No. 1432991 ; Department of Energy-Savannah River Nuclear Solution, Grant No. 0000217390
Faculty Advisor: B. K. Robertson, Ph.D., email@example.com
Role: I did the seasonal sampling, microbial isolation and culture. I also participated in developing the bulk part of the study, which include all the microbial methodologies.