2/24 – Rachel Poretsky, University of Illinois at Chicago

Speaker: Rachel Poretsky

Assistant Professor, Department of Biological Sciences, UIC

Title: Wastewater and stormwater influence microbial communities in urban aquatic systems

Abstract: Urban streams are susceptible to stormwater and sewage inputs that can impact their ecological health and water quality. Microbial communities in streams play important functional roles and their composition and metabolic potential can help assess ecological state and water quality. In this talk I will tell two stories about how microbial community composition, diversity, and functional potential is impacted by stormflow and wastewater. In the first study, we examined an urban stream during dry and wet weather conditions with both 16S rRNA gene sequencing across multiple years and shotgun metagenomics to more deeply analyze a single stormflow event. Results demonstrated general trends present in the stream under stormflow vs. baseflow conditions and also highlighted the influence of increased effluent flow following rain in shifting the stream microbial community from abundant freshwater taxa to those more associated with urban/anthropogenic settings. We also observed an increase in relative abundance of genes encoding degradation of organic pollutants and antibiotic resistance after rain. In the second study, we examined how wastewater treatment plants (WWTPs) release treated effluent containing mobile genetic elements (MGEs), antibiotic resistance genes (ARGs), and microorganisms into the environment. We characterized the genes and organisms from two different WWTPs that discharge into Lake Michigan, as well as from surrounding lake sediments to determine the dispersal and fate of these factors with respect to distance from the effluent outfall. Our results showed that the WWTPs likely influence the ARG composition in lake sediments close to the effluent discharge. Many of these ARGs were located on MGEs in both the effluent and sediment samples, indicating a relatively broad propensity for horizontal gene transfer (HGT). Overall, our results suggest a substantial influence of wastewater effluent and stormwater flow on gene content and microbial community structure in receiving urban water bodies.