Microbial Source Tracking; Library Independent Host-Specific Bacteroidales 16S rRNA Gene PCR Assay in a Mixed Use Watershed

Abstract

Transport of human and animal wastes into natural waters can result in contamination with fecal pathogens that are increasingly becoming a serious health risk. However, difficulties of differentiating sources of microbial pollutants limit the options to control the pollution. The goal of Microbial Source Tracking (MST) is to identify the source of microbial contamination in natural waters. My MST study was conducted using samples collected from The Upper Sugar Creek Watershed in Ohio. Samples were assayed using a PCR-based molecular method to detect and quantify the Bacteroidales 16S rRNA gene. . The Sugar Creek Watershed is a mixed-use watershed suitable to examine the source of microbial contamination from human and agricultural activity and/or wildlife. Host-specific Bacteroidales assays (human, ruminant, horse, pig, and dog) were used to determine potential host sources. A quantitative PCR (qPCR) assay for general Bacteroidales was used to investigate the magnitude of fecal contamination. Viable counts of E.coli were determined for statistical comparison with the Bacteroidales PCR assay. These data were analyzed along with land management data. We found frequent human specific signals at residential land use areas and also observed high magnitude of general Bacteroidales qPCR signals at concentrated livestock operation areas and in residential areas. The results indicate the potential application of the MST method to aid in making land management decisions to control microbial contamination at the watershed scale.