Date of Award


Degree Name

Master of Science


Biological Sciences

First Advisor

Dr. Silvia Rossbach

Second Advisor

Dr. Kathryn Docherty

Third Advisor

Dr. Yan Lu

Fourth Advisor

Dr. Brian Tripp


Petroleum, Biodegradation, 16S rRna, NifH, Magnetic Susceptibility

Access Setting

Masters Thesis-Abstract Only

Restricted to Campus until



Microbial biodegradation is an increasingly incorporated method of hydrocarbon mineralization during oil spill cleanup. To monitor biodegradation, magnetic susceptibility (MS) is a geophysical tool that detects changes in sediments’ magnetism, possibly caused by microbial activity, for example by anaerobic iron reduction that can induce magnetite formation. Furthermore, the high input of carbon from an oil spill makes other required nutrients, like nitrogen, limiting. The first study goal was to characterize the microbial communities present at high levels of MS with 16S rRNA gene clone libraries at the petroleum-contaminated site in Bemidji, Minnesota. Sequences with high similarity to known iron-reducers were found. In addition, sequences with high similarity to the syntrophic Smithella and the Archaeon Methanoregula were found, indicating methanogenic oil degradation. In a different approach, bacteria were isolated from the contaminated soil and identified with 16S rRNA sequencing. The second goal was to characterize nitrogen fixing populations present at the oil plume with nifH clone libraries. Sequences with high similarity to the nifH gene of rhizobia and other microorganisms associated with oil degradation were found. These results suggest that an increase in MS is directive towards active biodegradation, and that nitrogen fixation is performed by microorganisms involved in oil degradation.