title: Temporal assessment of the impact of exposure to cow feces in two watersheds by multiple host-specific PCR assays.
abstract: Exposure to feces in two watersheds with different management histories was assessed by tracking cattle feces bacterial populations using multiple host-specific PCR assays. In addition, environmental factors affecting the occurrence of these markers were identified. Each assay was performed using 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 the non-16S rRNA gene markers Bac1, Bac2, and Bac5 were found in 32 to 37% of the water samples. In contrast, all source-specific markers were detected in less than 6% of the water samples from WS2. Binary logistic regressions (BLRs) revealed that the occurrence of Bac32F and CF128F was significantly correlated with season as a temporal factor and watershed as a site factor. BLRs also indicated that the dynamics of fecal-source-tracking markers correlated with the density of a traditional fecal indicator (P < 0.001). Overall, our results suggest that a combination of 16S rRNA gene and non-16S rRNA gene markers provides a higher level of confidence for tracking unknown sources of fecal pollution in environmental samples. This study also provided practical insights for implementation of microbial source-tracking practices to determine sources of fecal pollution and the influence of environmental variables on the occurrence of source-specific markers.
authors.affiliation: National Research Council Research Associateship Programs, U.S. Environmental Protection Agency, Athens, Georgia 306051, USA.
authors.forename: Yong-Jin
authors.initials: YJ
authors.lastname: Lee
authors.forename: Marirosa
authors.initials: M
authors.lastname: Molina
authors.forename: Jorge W
authors.initials: JW
authors.lastname: Santo Domingo
authors.forename: Jonathan D
authors.initials: JD
authors.lastname: Willis
authors.forename: Michael
authors.initials: M
authors.lastname: Cyterski
authors.forename: Dinku M
authors.initials: DM
authors.lastname: Endale
authors.forename: Orin C
authors.initials: OC
authors.lastname: Shanks
mesh_terms: D000818:Animals; D002417:Cattle; D004269:DNA, Bacterial / Q000235:genetics / Q000302:isolation & purification; D004275:DNA, Ribosomal / Q000235:genetics / Q000302:isolation & purification; D005243:Feces / Q000382:microbiology*; D005843:Geography; D019015:Geologic Sediments / Q000382:microbiology*; D016133:Polymerase Chain Reaction / Q000379:methods; D012329:RNA, Bacterial / Q000235:genetics; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D012621:Seasons; D014871:Water Microbiology; D014876:Water Pollution
chemical_list: D004269:DNA, Bacterial; D004275:DNA, Ribosomal; D012329:RNA, Bacterial; D012336:RNA, Ribosomal, 16S