Room 1670 Beyster Building (North Campus)
Associate Professor Alexandria Boehm of the Department of Civil and Environmental Engineering at Stanford University will present, "Sunlight inactivation of enteric bacteria in seawater: Insights on rates and mechanisms from the field, lab, and models."
Diurnal variation in fecal indicator bacteria has been observed at numerous marine beaches and attributed to bacterial photoinactivation. However, little is known about the photoinactivation mechanisms responsible for the demise of cells during sunlit hours, limiting our ability to make predictions regarding the expected rates of photoinactivation in diverse environments. Generally, photoinactivation can occur via direct mechanisms primarily involving UV photons, or indirect mechanisms involving reactive species generated when photons of diverse wavelengths interact with sensitizing molecules external or internal to the cell.
The present study investigates the photoinactivation of enteric bacteria using field observations at a marine beach coupled to a fate and transport model, and laboratory experiments. Laboratory experiments investigate the relative importance of direct versus indirect inactivation in clear seawater, and examine cellular response to photostress by measuring changes in mRNA abundance during sunlight exposure using microarrays. Additional work explores how the presence of a pigment in Enterococcus (as can be found in E. casseliflavus, for example) affects its sensitivity to sunlight and photoinactivation rate.