Katelyn Downey

B.Sc. Student

Environmental Chemistry

Queen's University


Summer 2019 

Supervisor(s): Stephen Brown

Research Project: New methods for rapid detection of bacteria in water with interfering matrix components

Bacteria are detected by monitoring a fluorophore product from an indicator enzyme reaction where the enzyme should only be present in target bacteria (e.g. E.coli, fecal coliforms, or enterococci) in a test culture. Detection uses a polymer extraction step and a fibre-optic coupled fluorescence sensor. A matrix component like humic acid can interfere by inhibiting bacteria growth, by inhibiting the enzyme production of the fluorophore, or by affecting the extraction of the fluorophore into the polymer. The proposed research will entail controlled experiments isolating each of these steps to characterize the interference. We propose that signal reduction from interference with extraction can be used to estimate humic acid levels, and then to adjust for inhibition of growth to correct the results from the method. This will be tested with local surface water samples known to have various humic acid levels.