Prevalence of and relationship between two human-associated DNA biomarkers for bacteroidales in an urban watershed

Human-associated fecal biomarkers offer potent tools for the detection and control of human fecal pollution in watersheds. In some cases, the probability of false-negative findings may call for using a less specific biomarker that is present in higher quantities as long as it can be related to the more specific indicator. The objective of this study is to investigate the relationship between two previously published human-associated biomarkers for Bacteroidales bacteria in an urban watershed influenced by human fecal pollution and to determine if the less specific marker may be used to identify the locations of broken or leaking sewer lines. Samples were collected from 19 stream locations on 10 dates. Sample DNA was extracted and qPCR analysis was conducted for the HuBac and qHF183 biomarkers. The HuBac biomarker was detected more frequently than the qHF183 biomarker and in greater quantities when both were detected. A strong linear relationship (r² = 0.91) between the two markers was observed in 219 samples taken from both the watershed and inlet sewage. The relationship between the two biomarkers showed less variance at higher concentrations. However, even when the inlet sewage samples were excluded from the dataset, a clear linear relationship remained (r² = 0.74). The results indicate that use of a less specific, but more sensitive, biomarker may provide greater utility when the prevention of false negatives is necessary and the primary fecal source is known, as in spatial distribution studies of human fecal pollution in an urban watershed.