Thesis Title

Colonization of Biofilms in a Freshwater Stream by Fecal Coliforms and Escherichia Coli

Date of Graduation

Spring 2006


Master of Science in Biology



Committee Chair

John Steiert


Enteric bacterial contamination was assessed along one area of Wilson’s Creek comparing bacterial levels found in the water column with those found in biofilm. Samples were collected 5 times per month for 7 months, and analyzed for fecal coliform and E. coli. A biofilm collection device was constructed using removable plates to grow biofilm, which were then transported to the laboratory and submitted to bacterial separated procedures. Using routine bacteriological analysis procedures, levels of fecal coliform and E. coli from both the water column and biofilm were determined. Each sampling date, turbidity, air temperature, water temperature, pH, dissolved oxygen, flow rate, and nutrient concentrations were measured. The presence of pathogenic strains; Salmonella, Shigella, and E. coli were determined from biofilm samples using molecular methods. Correlation analysis indicated bacterial levels in the water column are influenced by turbidity and phosphorus, while bacterial levels in biofilm correlated with dissolved oxygen and flow. Median counts for water column E. coli exceeded EPA established limits of 126 CFU/100mL set for recreational waters every month. Median fecal coliform levels in the water column exceeded EPA limits of 200 CFU/100mL for 6 of the 7 sample months. Bacterial levels in the water column peaked during summer months, decreasing with water temperature. Biofilm bacterial numbers remained constant or increased despite low temperatures, suggesting added survivability and environmental resistance when incorporated in biofilm. Pathogenic strains, Salmonella and Shigella, were detected in biofilm; however, no samples tested positive for E. coli.


fecal coliform, E. coli, biofilm, Salmonella, Shigella

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© Brian R. McMinn