In aquatic environments, many organisms, including bacteria, are affected by polluted runoff. The Jones Falls, a tributary that flows into the Chesapeake Bay, is severely impacted by a variety of problems, including a high amount of surrounding impervious surface and stormwater runoff. Bacteria from the stream were isolated, characterized, and subjected to experiments designed to challenge them in media containing used motor oil. Microbial growth was measured (OD₅₉₀) after this exposure. It was hypothesized that given that the native bacteria in the Jones Falls were likely previously exposed to used motor oil from urban runoff, some species would favor repeated laboratory treatment with used motor oil. The results of growth curve experiments suggest that some bacterial isolates display hindered growth while others display enhanced growth after exposure to used motor oil. Given that microorganisms are the base of the food web, their responses to a changed environment can potentially affect the rest of the aquatic ecosystem. Learning about the microbial species affected by various components of stormwater runoff can aid in identifying release locations and informing mitigation methods.