Quantitative identification of fecal water pollution sources by TaqMan real-time PCR assays using Bacteroidales 16S rRNA genetic markers |
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Authors: | Dae-Young Lee Susan C Weir Hung Lee Jack T Trevors |
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Institution: | (1) School of Environmental Sciences, University of Guelph, Guelph, ON, Canada, N1G 2W1;(2) Laboratory Services Branch, Ontario Ministry of the Environment, Etobicoke, ON, Canada, M9P 3V6; |
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Abstract: | PCR-based analysis of Bacteroidales 16S rRNA genes has emerged as a promising tool to identify sources of fecal water pollution. In this study, three TaqMan
real-time PCR assays (BacGeneral, BacHuman, and BacBovine) were developed and evaluated for their ability to quantitatively
detect general (total), human-specific, and bovine-specific Bacteroidales 16S rRNA genetic markers. The detection sensitivity was determined to be 6.5 copies of 16S rRNA gene for the BacGeneral and
BacHuman assays and 10 copies for the BacBovine assay. The assays were capable of detecting approximately one to two cells
per PCR. When tested with 70 fecal samples from various sources (human, cattle, pig, deer, dog, cat, goose, gull, horse, and
raccoon), the three assays positively identified the target markers in all samples without any false-negative results. The
BacHuman and BacBovine assays exhibited false-positive reactions with non-target samples in a few cases. However, the level
of the false-positive reactions was about 50 times smaller than that of the true-positive ones, and therefore, these cross-reactions
were unlikely to cause misidentifications of the fecal pollution sources. Microbial source-tracking capability was tested
at two freshwater streams of which water quality was influenced by human and cattle feces, respectively. The assays accurately
detected the presence of the corresponding host-specific markers upon fecal pollution and the persistence of the markers in
downstream areas. The assays are expected to reliably determine human and bovine fecal pollution sources in environmental
water samples. |
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