MONITORING FECAL CONCENTRATIONS AND SOURCES IN STREAMS USING REAL-TIME PCR ASSAYS FOR BACTEROIDES

A multi-disciplinary group of researchers at the University of Tennessee is developing and testing a series of different microbial assay methods based on real-time PCR to detect fecal bacterial concentrations and host sources in water samples. Real-time PCR is an enumeration technique based on the unique and conserved nucleic acid sequences present in all organisms. The first research task was development of an assay (AllBac) to detect Bacteroides, which represents up to 30% of fecal mass. Subsequent assays were developed to detect Bacteroides from cattle (BoBac) and humans (HuBac) using 16sRNA genes based on DNA sequences in the national GenBank, as well as sequences from local fecal samples. The assays potentially have significant advantages over conventional bacterial source tracking methods because: 1. unlike traditional enumeration methods, they do not require bacterial cultivation; 2. there are no known non-fecal sources of Bacteroides; 3. the assays are quantitative with results for total concentration and for each species expressed in mg/l; and 4. they show little regional variation within host species, meaning that they do not require development of extensive local gene libraries. The AllBac and BoBac assays have been used in a study of fecal contamination in a small rural watershed (Stock Creek) near Knoxville, TN, and have proven useful in identification of areas where cattle represent a significant fecal input and in development of BMPs. It is expected that these types of assays (and future assays for birds, hogs, etc.) could have broad applications in monitoring fecal impacts from Animal Feeding Operations, as well as from wildlife and human sources.