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Morales, Sergio E.

Microbiology and Molecular Genetics

2006

PhD

Wetlands are major sources of carbon dioxide, methane and other greenhouse gases released during microbial degradation. Despite the fact that decomposition is driven mainly by bacteria and fungi, little is known about the taxonomic diversity of bacterial communities in wetlands, particularly Sphagnum bogs. In order to explore bacterial community composition, and as part of a multidisciplinary effort to study the effect of nitrogen deposition in these wetlands, twenty-four bogs in Vermont and Massachusetts were censused for bacterial diversity at the surface (oxic) and 1 meter (anoxic) regions. Bacterial diversity was characterized by a T-RFLP fingerprinting technique and a cloning strategy that targeted the 16S rRNA gene, and abundance was estimated by means of fluorescent microscopy. Data was analyzed using multivariate analysis, phylogenetic placement tools and statistical analysis. Results pointed to a robust community independent of depth and site. Over a sample size of 24 different wetlands, the variance in the community was minimal with only one truly different site identified (Chickering), which happened to match the profile for a transient fen. This is encouraging because it would indicate that studies done in a subset of bogs could yield data that can be extrapolated for other sites within the same region or even at a global scale. It was shown based on multivariate analysis of the T-RFLP data that anoxic layers possess a unique community which shares members with oxic levels but portrays a different profile. Finally, phylogenetic analysis of the 16S clone library gave indirect evidence for methanogenesis and methane oxidation as having a central role in the sampled site.