title: Biotic interactions and sunlight affect persistence of fecal indicator bacteria and microbial source tracking genetic markers in the upper Mississippi river.
abstract: The sanitary quality of recreational waters that may be impacted by sewage is assessed by enumerating fecal indicator bacteria (FIB) (Escherichia coli and enterococci); these organisms are found in the gastrointestinal tracts of humans and many other animals, and hence their presence provides no information about the pollution source. Microbial source tracking (MST) methods can discriminate between different pollution sources, providing critical information to water quality managers, but relatively little is known about factors influencing the decay of FIB and MST genetic markers following release into aquatic environments. An in situ mesocosm was deployed at a temperate recreational beach in the Mississippi River to evaluate the effects of ambient sunlight and biotic interactions (predation, competition, and viral lysis) on the decay of culture-based FIB, as well as molecularly based FIB (Entero1a and GenBac3) and human-associated MST genetic markers (HF183 and HumM2) measured by quantitative real-time PCR (qPCR). In general, culturable FIB decayed the fastest, while molecularly based FIB and human-associated genetic markers decayed more slowly. There was a strong correlation between the decay of molecularly based FIB and that of human-associated genetic markers (r(2), 0.96 to 0.98; P < 0.0001) but not between culturable FIB and any qPCR measurement. Overall, exposure to ambient sunlight may be an important factor in the early-stage decay dynamics but generally was not after continued exposure (i.e., after 120 h), when biotic interactions tended to be the only/major influential determinant of persistence.
authors.affiliation: National Exposure Research Laboratory, Office of Research and Development, U.S. Environmental Protection Agency, Cincinnati, Ohio, USA korajkic.asja@epa.gov.
authors.forename: Asja
authors.initials: A
authors.lastname: Korajkic
authors.affiliation: National Exposure Research Laboratory, Office of Research and Development, U.S. Environmental Protection Agency, Cincinnati, Ohio, USA.
authors.forename: Brian R
authors.initials: BR
authors.lastname: McMinn
authors.affiliation: National Risk Management Research Laboratory, Office of Research and Development, U.S. Environmental Protection Agency, Cincinnati, Ohio, USA.
authors.forename: Orin C
authors.initials: OC
authors.lastname: Shanks
authors.affiliation: National Risk Management Research Laboratory, Office of Research and Development, U.S. Environmental Protection Agency, Cincinnati, Ohio, USA.
authors.forename: Mano
authors.initials: M
authors.lastname: Sivaganesan
authors.affiliation: National Exposure Research Laboratory, Office of Research and Development, U.S. Environmental Protection Agency, Cincinnati, Ohio, USA.
authors.forename: G Shay
authors.initials: GS
authors.lastname: Fout
authors.affiliation: National Exposure Research Laboratory, Office of Research and Development, U.S. Environmental Protection Agency, Cincinnati, Ohio, USA.
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Ashbolt
mesh_terms: D000818:Animals; D001431:Bacteriological Techniques; D016172:DNA Fingerprinting; D016983:Enterococcus / Q000145:classification / Q000302:isolation & purification* / Q000528:radiation effects; D004926:Escherichia coli / Q000145:classification / Q000302:isolation & purification* / Q000528:radiation effects; D005243:Feces / Q000382:microbiology*; D005819:Genetic Markers; D006801:Humans; D060888:Real-Time Polymerase Chain Reaction; D045483:Rivers / Q000382:microbiology*; D013472:Sunlight; D014873:Water Pollutants
chemical_list: D005819:Genetic Markers; D014873:Water Pollutants
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