LE3 .A278 2013

2013

Smith, Todd

Acadia University

Bachelor of Science

Honours

Biology

Biology

The waters and stream sediments of Thomas Brook, a sub-catchment of the Cornwallis River Watershed, are chronically contaminated with Escherichia coli. Various sources for this indicator bacterium have been suggested and assessed. However, the role of insects in introducing and maintaining populations within the brook and the surrounding environment has not yet been evaluated. The objective of this study was to determine whether insects emerging from Thomas Brook water carry generic E. coli. Intercept insect traps were used to collect species emerging from the brook. Weekly water and insect samples were collected at three separate sites along the brook and screened for their carriage of culturable E. coli or its DNA. Specific PCR primers were used to amplify a DNA fragment unique to E. coli. Confirmed E. coli colonies were further characterized using primers for three marker genes, the presence or absence of which enabled their placement in specific phylogenetic groups. Escherichia coli DNA was confirmed in 12 of 49 (24.5%) composite insect samples. Of the positive samples, the most prevalent insects were true flies and beetles. The majority, 73/138 (52.9%), of E. coli colonies recovered from water samples belonged to the B1 phylogenetic group, while 62/90 (68.9%) of those from insect samples were of the Group D. Members of groups A and B1 were not detected among insect isolates. DNA fingerprinting of the common phylogenetic groups allowed testing of the degree of genetic similarity between insect and water isolates. In one case, a similar banding pattern (89% similarity coefficient) was found between a water and three insect isolates, indicating a strong relationship between the four strains. More intensive sampling of insect species and surrounding areas would provide greater insight into their potential role in E. coli dissemination.

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https://scholar.acadiau.ca/islandora/object/theses:1043