Persistence of Bacteroides ovatus under simulated sunlight irradiation

Abstract

BackgroundBacteroides ovatus, a member of the genus Bacteroides, is considered for use in molecular-based methods as a general fecal indicator. However, knowledge on its fate and persistence after a fecal contamination event remains limited. In this study, the persistence of B. ovatus was evaluated under simulated sunlight exposure and in conditions similar to freshwater 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 and absence of exogenous photosensitizers and in salinity up to 39.5 parts per thousand at 27°C.ResultsUVB was found to be important for B. ovatus decay, averaging a 4 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 in both low and high salinity water, while the exogenous sensitizer algae organic matter (AOM) slowed down the decay of B. ovatus in low salinity water. At seawater salinity, the decay rate of B. ovatus was slower than that in low salinity water, except when both NaNO2 and AOM were present.ConclusionThe results of laboratory experiments suggest that if B. ovatus is released into either freshwater or seawater environment in the evening, 50% of it may be intact by the next morning; if it is released at noon, only 50% may be intact after a mere 5 min of full spectrum irradiation on a clear day. This study provides a mechanistic understanding to some of the important environmental relevant factors that influenced the inactivation kinetics of B. ovatus in the presence of sunlight irradiation, and would facilitate the use of B. ovatus to indicate the occurrence of fecal contamination.

Molecular-based approaches to characterize coastal microbial community and their potential relation to the trophic state of Red Sea

“…The low abundance of these genera detected by molecular methods may be due to prolonged natural inactivation and decay of the bacterial cells and their respective genomic signatures upon sunlight irradiation232425. Alternatively, these genera may be associated with the big particulate fractions of the seawater and inadvertently removed when filtering the water samples through an 8 μm filter prior to the 0.45 μm filter.…”

Staphylococcus aureus Strain Newman Photoinactivation and Cellular Response to Sunlight Exposure

“…The seawater was made using molecular biology reagent water (Sigma-Aldrich, St. Louis, MO) and was filter sterilized using Millipore Steritop filter units (polyethersulfone [PES] filter; 0.22-m pore size [Millipore, Darmstadt, Germany]). Simulated seawater was used to control the chemistry of the aqueous phase throughout the experiment and to ensure there were no exogenous sensitizers present in the water (4,57,58).…”

Assessing the Groundwater Quality at a Saudi Arabian Agricultural Site and the Occurrence of Opportunistic Pathogens on Irrigated Food Produce

“…This may be due to the inability to resuscitate and grow viable but non-culturable coliforms that were stressed or injured in the environmental water matrix [ 45 ]. In addition, DNA detected by molecular-based qPCR approaches has a longer persistence than the viable cells [ 45 , 46 ]. This in turn enabled detection of the gene markers, but a positive detection may not be representative of a recent contamination event.…”