Lee Yong-Jin, Molina Marirosa, Santo Domingo Jorge W, Willis Jonathan D, Cyterski Michael, Endale Dinku M, Shanks Orin C
National Research Council Research Associateship Programs, U.S. Environmental Protection Agency, Athens, Georgia 306051, USA.
Appl Environ Microbiol. 2008 Nov;74(22):6839-47. doi: 10.1128/AEM.00601-08. Epub 2008 Sep 19.
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.
通过使用多种宿主特异性聚合酶链反应（PCR）检测方法追踪牛粪细菌种群，评估了两个具有不同管理历史的流域中粪便的暴露情况。此外，还确定了影响这些标志物出现的环境因素。每种检测方法均使用从直接受牛粪污染的流域（WS1）以及仅通过径流受影响的流域（WS2）采集的水和沉积物样本的DNA提取物进行。在WS1中，65%的水样中检测到反刍动物特异性拟杆菌16S rRNA基因标志物CF128F，而在32%至37%的水样中发现了非16S rRNA基因标志物Bac1、Bac2和Bac5。相比之下，在WS2的水样中，所有源特异性标志物的检测率均低于6%。二元逻辑回归（BLR）显示，Bac32F和CF128F的出现与作为时间因素的季节以及作为地点因素的流域显著相关。BLR还表明，粪便源追踪标志物的动态变化与传统粪便指示物的密度相关（P < 0.001）。总体而言，我们的结果表明，16S rRNA基因和非16S rRNA基因标志物的组合为追踪环境样本中未知粪便污染源提供了更高的置信度。本研究还为实施微生物源追踪实践以确定粪便污染源以及环境变量对源特异性标志物出现的影响提供了实际见解。
