METHANOGENS AS INDICATORS OF SURFACE WATER FECAL POLLUTION

Tracking the source of fecal pollution in surface waters has traditionally focused on the origin of enteric indicators including coliforms, enterococci, or Escherichia coli. Recently, questions of genetic variability and environmental persistence have encouraged researchers to search for additional animal specific indicators of fecal pollution. To date only eubacteria have been utilized as markers of human and animal-specific pollution. Here we report a molecular primer set specific to Methanomicrobium mobile, a methanogen found in the ruminant intestine. PCR primers for the mcrA gene of M. mobile specific to the bovine intestine were designed, tested, and used to detect the presence or absence of this organism in fecal and environmental samples. The presence of M. mobile was observed in 87% of all bovine fecal samples, 100% cow lagoon samples, and 100% creek water contaminated with bovine feces. No amplification was observed when primers were tested against 43 bacterial stock cultures and fecal samples from 150 different animals. Sequencing of PCR products from bovine feces demonstrated that the observed product was the mcrA gene of M. mobile. Sensitivity assays demonstrated a detection limit of 1pg total DNA in bovine feces, 10ng in fecally contaminated water, and 5ng in cow lagoon samples. This study shows the usefulness of a previously overlooked organism, M. mobile, in determining levels of bovine fecal contamination in surface waters.