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INFLUENCE OF EQUINE FECAL CONTAMINATION ON MICROBIAL COMMUNITY STRUCTURE IN A SUB-WATERSHED
Citation:
Simpson*, J M. AND J Santo Domingo. INFLUENCE OF EQUINE FECAL CONTAMINATION ON MICROBIAL COMMUNITY STRUCTURE IN A SUB-WATERSHED. Presented at American Society for Microbiology 102nd General Meeting, Salt Lake City, UT, 5/19-23/2002.
Description:
As monitoring of watershed water quality is directly related to proposed uses, it is important for our Naton's water systems that the d4etemrination of and distinction between fecal contamination source is made. The most common water quality monitoring approach is to screen for fecal indicator bacteria using culturing methods. However, these methods can not distinguish between contaminant sources. Molecular methods are being applied in an attempt to better determine sources of fecal contamination using potential 16S rDNA targets. Denaturing gradient gel electrophoresis (DGGE) targeting the V3 variable region of the 16S rDNA gene was used to examine differences between microbial community structure in water samples obtained from upstream and downstream of a distinct and discreet equine fecal contamination source. Water samples were collected for four months from 20 m upstream and 5, 10, and 20 m downstream from contamination sorce. As an indication of contamination level, fecal Enterococci were enumerated and increased from (Log10) 1.4 CFU/ml upstream to 8.1 CFU/ml downstream. Resulting DGGE profiles were compared using Sorenson's index, a pairwise similarity coefficient (Cs). Upstream samples had more DGGE banding pattern variation than downstream samples during the four month period and averaged a Cs of 42% +/- 13. Samples collected from downsream had greater pattern similarity and averaged a Cs of 70% +/- 11. Within single sample collection sets, downstream samples had more stable similarity irrespective of distance from source, averaging a Cs of 77% +/- 5. This change in pattern similarity and stability suggests that the influx of fecal bacteria from the equine manure not only alters the microbial community structure locally, but also maintains an influence on the bacterial community downstream. Identifying predominant bacterial species persisting within the watershed after a fecal contamination event may allow selection of the appropriate microorganism(s) for use in identifying fecal contamination sources, which would be invaluable to improvement of water quality.