Honors College Theses




Biology (B.S.B.)

Document Type and Release Option

Thesis (restricted to Georgia Southern)

Faculty Mentor

Dr. Tiehang Wu


Microbial communities found in soil organic matter have for so long been recognized in aiding the recycling and decomposition of nutrients in the ecosystem. Both biotic factors, such as plant species, and abiotic factors, such as soil physical and chemical properties, affect the diversity and functional genes of the soil microbial community. A clear understanding on how biotic and abiotic factors influence the microbial community and its functional role in terrestrial ecosystems is fundamental to terrestrial biogeochemistry. The purpose of this experiment was to investigate total and denitrifying bacteria amongst varying groundwater depth plots and tree species: Eucalypt and Pine. The total soil bacterial 16 rRNA gene, denitrifying bacterial nirK, nosZ and nirS genes were detected using PCR (PCR) and Denaturing Gradient Gel Electrophoresis (DGGE). Using DGGE analysis, microbial communities were analyzed through the separation of PCR-amplified products of soil bacterial 16 rRNA gene and genes (nirK, nosZ and nirS), which migrated and stopped at different positions. Soil bacterial community structure remained similar between the forest plantation types, but differed between groundwater depths. The abundant nirK and nosZ genes were detected, whereas, the nirS gene was not detected and only produced little to no bands. Overall, the denitrification community varied significantly with respect to water levels. There was no difference of overall denitrifying bacterial community between different forest plantation types. The different microbial community observed within two forest plantations and at shallow and deep groundwater depths may provide important information for the intensity of management and planting a woody crop eucalypt species with even higher production potential than loblolly pine