Honors Theses
Date of Award
2009
Document Type
Undergraduate Thesis
Department
History
First Advisor
Colin Jackson
Relational Format
Dissertation/Thesis
Abstract
What is currently known about bacterial diversity of the phyllosphere has largely come from studies of plants involved in commercial agriculture. With very few studies dedicated to examining phyllosphere bacterial communities of natural forests, the issue of seasonal changes in bacterial communities in Magnolia gvandifloi'a leaf phyllosphere was investigated. In order to examine the issue, 16S rRNA sequencing techniques were used to identify and compare bacterial communities between leaf samples collected in February, May, August and December of 2008. When M. grandiflora DNA samples were examined with denaturing gel electrophoresis (DGGE), similarities between the bacterial communities of each leaf could be determined. A February 2008 sample was used to create a 16S rRNA clone library, and sequence data from this library allowed for the identity of bacteria in the phyllosphere to be determined. Binary DGGE data was used to examine similarities between each leaf sample using cluster analysis, multidimensional scaling (MDS) and Jaccard similarity. These various forms of analysis all showed that there was a significant difference in the bacterial communities of M. grandiflora phyllosphere between seasons, and there were varying degrees of similarity between leaves of the same season. The seasonal variance in bacterial communities of M grandiflora leaf phyllosphere may be due to seasonal changes in the canopy of the forest, as samples were taken from trees growing in the understory, that cause changes in environmental factors such as sunlight or precipitation. The seasonal variation may also be a product of various bacteria being more adapted to the temperatures and environmental conditions of various seasons. The 16S rRNA clone library created from a February sample produced 85 usable gene sequences that were each identified using BLAST searches to GenBank. These 85 clone sequences were identified as bacteria existing in six different phyla and classes, as well as some chloroplast DNA and unknown environmental bacteria. The dominant bacteria identified were in phyla Proteobacteria, Actinobacteria. and Bacteroidetes. The most dominant phyla was Proteobacteria and all identified Proteobacteria were of the class Alphaproteobacteria. The sequencing of the 16S rRNA clone library shows that the bacteria present in M grandiflora phyllosphere is dominated by Alphaproteobacteria and also includes several other soil bacteria. While the February sequence data identifies the bacteria present during that season, the apparent changes revealed by DGGE suggest that more extensive sequence analysis, looking at sequences found in each season, is warranted.
Recommended Citation
Denney, William Craig, "Seasonal Changes in Bacterial Communities in Magnolia (Magnolia grandiflora) Leaf Phyllosphere" (2009). Honors Theses. 2315.
https://egrove.olemiss.edu/hon_thesis/2315
Accessibility Status
Searchable text