Persistence of Bacteroides ovatus under simulated sunlight irradiation
The persistence of Bacteroides ovatus, a human-associated anaerobic fecal contamination indicator bacteria species, was evaluated under simulated sunlight exposure and conditions similar to surface water and seawater. By combining propidium monoazide (PMA) treatment and quantitative polymerase chain reaction (qPCR) detection, the decay rates of B. ovatus were determined in the presence of exogenous photosensitizers and salinity up to 39.5 parts per thousand at 27oC. UVB was found to be important for B.ovatus decay, averaging a four log10 of decay over 6 h of exposure without the presence of extracellular photosensitizers. The addition of NaNO2, an exogenous sensitizer producing hydroxyl radicals, did not significantly change the decay rate of B. ovatus, while the exogenous sensitizer algae organic matter (AOM) slowed down the decay of B. ovatus. At seawater salinity, the decay rate of B. ovatus is either slower than or as fast as that at freshwater salinity. Exogenous photosensitizers did not accelerate B. ovatus decay when being present alone in both low and high salinity solutions. Our study suggests that different B.ovatus persistence exists between light and dark treatment: if it is released into either the water or seawater environment in the evening, 50% of it will still be alive by the next morning; if it is released at noon, only 50% will be alive after mere 5 min of full spectrum irradiation on a clear day.
Bacteroides ovatus, natural organic matter, algae, hydroxyl radicals, salinity, simulated sunlight, Persistence
University of Illinois - Urbana-Champaign
Networked Digital Library of Theses and Dissertations
University of Illinois at Urbana-Champaign