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Publication Date


Document Type

Honors Project


Biological Sciences


Bacteria-Classification, Biodiversity, Pond ecology, Sulfate-reducing bacteria, Methylmercury, Biotic communities, Microbial community, Beaver ponds, 16S SSU, Dissimilatory sulfite reductase, Bacterial diversity, Biotic interactions, Avery Brook (Conway, Mass.)


Beaver ponds, which result from the activities of the North American Beaver (Castor canadensis), can have important environmental effects. These wetland systems are highly dynamic and have been identified as "hotspots" of bacteriallymediated chemical cycling. This study is an exploration of the bacterial diversity of beaver pond sediments, using molecular techniques analyzing 16S rRNA and dissimilatory sulfite reductase (dsr) genes. An SSU-based clone library was constructed to catalog a diverse array of bacteria, and a dsrA-based clone library was constructed to target sulfate-reducing bacteria (SRB). We discovered that the bacteria in these sediments are hyper-diverse (Simpson's D=0.007 to 0.01), span the breadth of the bacterial phylogeny, and have high rates of novelty (61.9%). The SRB are also diverse (D=0.01 to 0.08), though not as acutely as the total bacterial community. The SRB community has an exceptionally high rate of novelty (85.2%). The SRB in these sediments appear to be members of the Firmicutes and the Deltaproteobacteria, consistent with previous studies of SRB phylogenies. No SRB were directly identified through 16S SSU analysis, but many members of the aforementioned bacterial phyla were identified, suggesting that SRB may have been found via SSU, but were too distant from cultured representatives to be positively identified as such.




68 p. : ill. (chiefly col.) Honors Project-Smith College, Northampton, Mass., 2011. Includes bibliographical references (p. 60-68)