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Biotic interactions and sunlight affect persistence of fecal indicator bacteria and microbial source tracking genetic markers in the Upper Mississippi River
Citation:
Korajkic, A., B. McMinn, O. Shanks, Mano Sivaganesan, Shay Fout, AND N. Ashbolt. Biotic interactions and sunlight affect persistence of fecal indicator bacteria and microbial source tracking genetic markers in the Upper Mississippi River. APPLIED AND ENVIRONMENTAL MICROBIOLOGY. American Society for Microbiology, Washington, DC, 80(13):3952-3961, (2014).
Impact/Purpose:
This article described findings from the decay study investigating the effect of indigenous river microbiota and ambient sunlight on fecal indicator bacteria (by culture and by PCR), as well as select human-associated genetic MST markers.
Description:
Sanitary quality of recreational waters is assessed by enumerating fecal indicator bacteria (FIB) (Escherichia coli and enterococci); organisms present in the gastrointestinal tract of humans and many other animals, hence providing no information about the pollution source. Microbial source tracking (MST) methods can discriminate between different pollution sources providing critical information to water quality managers. However, relatively little is known about factors influencing the relative decay of FIB and MST genetic markers following release into aquatic environments. An in situ, submerged mesocosm was deployed at a temperate recreational beach in the Mississippi River to mimic conditions for municipal wastewater released into ambient waters and to evaluate select environmental variables on decay of culture-based FIB measurements, as well as molecular-based FIB (Entero1a, GenBac3) and human-associated MST genetic markers (HF183, HumM2) measured by quantitative real-time PCR (qPCR). Treatment variables included exposure to: (1) ambient sunlight and indigenous river microbiota, (2) indigenous river microbiota only, (3) ambient sunlight only and (4) neither variable. In general, culturable FIB decayed the fastest, while molecular-based FIB and human-associated genetic markers decayed to a lesser extent. There was a strong correlation between decay of molecular based FIB and human-associated genetic markers (r2 0.96-0.98, 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 not after continued exposure (i.e. after 120 h) when indigenous river microbiota tended to be the only/major influential determinant of persistence.
