Murray State Theses and Dissertations


Reservoirs, including Kentucky Lake, are unique in that they do not follow a natural cycle of rising during the rainy seasons and dropping during the dry summers. The lake is manipulated, mainly for flood control and transportation, so that the water level is increased during the summer months and decreased during the winter months. This manipulation leaves the littoral sediment of the lake submerged in the summer and exposed in the winter. The seasonal water level, along with other factors, like farming practices in the watershed, contributes to the availability of nutrients for organisms inhabiting the sediment of the lake. These littoral zone sediment, microbial communities are also not well understood. The Archaeal community of the Ledbetter Creek embayment, Kentucky Lake, has been the topic of study by several MSU students using sequence analysis of cloned 16S rDNA. BLAST searches showed species like the methanogen Methanosaeta concillii were the most abundant Archaea in this environment in 2007. Further, it was found that of the 59 M. concillii-like clones sequenced, 50 were unique species (using 98.7% sequence identity as the cutoff). The aim of this study was to again examine the Archaeal community in this environment to determine whether Methanosaeta concillii-like species continue to dominate the Archaeal community and to compare these sequences to those found in the previous study. DNA was extracted from sediment samples; the 16S rDNA genes were amplified using Archaeal specific primers and cloned. The cloned inserts were sequenced and compared to the Genebank database and the M. concilli-like sequences found previously. The results from this study show that the Methanosaeta concilli-like species remain abundant in these samples, but are not the same species found before, using the 98.7% identity cutoff. The results of this study also found that there is another group of archaea that were abundant in this environment, Methanoregula boonei-like organisms. These data suggest that the Archaeal community is continually in flux in that the organisms are very closely related to those found in 2007 and may be derivatives, but the species change with time.

Year manuscript completed


Year degree awarded


Author's Keywords

Archaea, Methanogen, Methanosaeta concilii, Kentucky lake

Thesis Advisor

Timothy C. Johnston

Committee Member

Chris Trzepacz

Committee Member

Alexey Arkov

Committee Member

Edmund J. Zimmerer

Committee Member

David Ferguson

Document Type