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Temporal Assessment of the Impact of Exposure to Cow Feces inTwo Watersheds by Multiple Host-Specific PCR Assays
Citation:
Yong-Jin, L., M. MOLINA, J. W. SANTO-DOMINGO, J. D. WILLIS, M. CYTERSKI, D. M. Endale, AND O. C. SHANKS. Temporal Assessment of the Impact of Exposure to Cow Feces inTwo Watersheds by Multiple Host-Specific PCR Assays . APPLIED AND ENVIRONMENTAL MICROBIOLOGY. American Society for Microbiology, Washington, DC, 74(22):6839-6847, (2008).
Impact/Purpose:
To share information
Description:
Fecal exposure in two watersheds with different management histories was assessed by tracking cattle fecal bacterial populations using multiple host-specific PCR assays. In addition, environmental factors affecting the occurrence of these markers were identified. Each assay was tested against DNA extracts from water and sediment samples collected from a watershed directly impacted by cattle fecal pollution (WS1) and from a watershed impacted only through runoff (WS2). In WS1, the ruminant-specific Bacteroidales 16S rRNA gene marker CF128F was detected in 65% of the water samples, while non-16S rRNA gene markers Bac1, Bac2 and Bac5 were found in 32-37% of the water samples. In contrast, all source-specific markers were detected in less than 6% of the water samples in WS2. Binary logistic regressions (BLRs) revealed that the occurrence of Bac32F and CF128F were significantly correlated with season as a temporal factor and watershed as a site factor. BLRs also indicate that the dynamics of fecal source tracking markers correlate with the density of a traditional fecal indicator (P < 0.001). Overall, our results suggest that a combination of both 16S rRNA gene and non-16S rRNA gene markers offers a higher level of confidence for tracking unknown sources of fecal pollution in environmental samples. This study also provides practical insights into the implementation of MST practices to source fecal pollution and the influence of environmental variables on the occurrence of source-specific markers.
