CAREER: Photolysis of intracellular and extracellular antibiotic resistance genes in the environment

The spread of antibiotic resistant bacteria (ARB) that cause infections resistant to treatment with antibiotics is a growing global public health threat. Antibiotic resistance genes (ARG) are the DNA molecules within ARB that code for antibiotic resistance. Monitoring of ARG in the Nation's waterways has increased as they are now considered a "contaminant of emerging concern". Despite their prevalence, there is limited information on ARG persistence and decay in surface waters. The objective of the proposed work is to fill this critical gap in our understanding of ARG risk. This will be achieved by evaluating the rates and mechanisms of ARG decay in surface water focusing on sunlight-mediated reactions. Results will provide the necessary information to predict public health risk due to ARG. Further benefits include the ability to identify key environmental control points for surveillance and deployment of treatment technologies. Integrated with this research will be an educational program that includes new courses and activities for high school and college students. The goal of which is to train the next generation of environmental engineers. Outreach will increase scientific literacy and public awareness of ARG and the connections between the environment and public health.<br/><br/>Sunlight-driven photolysis is an important process for the degradation of many microorganisms and organic molecules. Therefore, the underlying hypothesis for this research project is that ARG will undergo degradation in the environment due to photolysis, and that decay rates and the dominant photolysis mechanism will vary among ARG depending on their DNA sequence and the environmental conditions such as water chemistry and incident irradiance. To evaluate this hypothesis, the research objectives are to: 1) systematically evaluate direct photolysis, indirect photolysis, and sunlight-independent decay of key ARG under simulated sunlight and a range of environmental and water quality conditions; 2) conduct bacterial transformation experiments with sunlight-exposed ARG to determine whether a reduction in the quantitative PCR (qPCR) signal for an ARG corresponds to a reduction in its gene function; 3) use experimental data to develop broadly applicable numerical models that can predict photolysis rates of ARG under different environmental conditions; and 4) investigate the effect of DNA sequence on direct photolysis rates through the use of a novel sequencing-based assay to map the locations of sunlight-induced damage (e.g., formation of cyclobutane pyrimidine dimers) on each DNA target. The integrated education component of this project will include research and course-based activities for high school, undergraduate, and graduate students that incorporate antibiotic resistance concepts, and introduce students to the field of environmental engineering. The PI will also develop and disseminate an engaging class module for high school students on the urban water cycle that will incorporate findings from the proposed research, and highlight engineering in service to society and the connections between the environment and public health.<br/><br/>This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.