Identifying the Sources of Escherichia coli in Lake Whatcom, Bellingham, Washington Using Amplified Fragment Length Polymorphism (ALFP) Analysis

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Higginson, Lesli
Lake Whatcom; Water quality; Amplified Fragment Length Polymorphism (ALFP) analysis; E. coli; Biology
thesis / dissertation description
Amplified fragment length polymorphism (AFLP) analysis was applied to a bacterial source tracking study at Lake Whatcom, Bellingham, Washington to determine if humans, dogs, Canada geese, or all three animal sources were contributing to the Escherichia coli contamination in the lake. E. coli were isolated from Lake Whatcom surface waters, sediment samples, and the three potential animal sources. Genomic DNA extracted from the E. coli isolates was analyzed using the AFLP technique. Fragments produced by a restriction digest using two restriction endonucleases were ligated to double stranded-adapter molecules that served as primer binding sites for two subsequent polymerase chain reactions. Three AFLP data sets were generated, one with primer pair EcoRI-A/MseI-C, the second with primer pair EcoRI-A/MseI-G, and the third, a composite data set created by combining the results from the two primer sets. Principal components analysis and cluster analysis of AFLP data showed three groupings of the E. coli isolates. E. coli isolates from goose feces had the highest number of correctly classified isolates, up to 84%. Approximately half of the isolates from human feces and 19-35% of the isolates from dog feces classified correctly. The analysis of the composite data set showed that Canada geese were the major source of fecal contamination at the Bloedel Donovan swim area on Lake Whatcom.