COLLEGE OF SCIENCES

SCHOOL OF EARTH AND ATMOSPHERIC SCIENCES

EAS Ph.D. Defense

Boryoung Shin

March 15, 2018

1:00 PM

Earth and Atmospheric Sciences

Ford Environmental Science & Technology (ES&T)311 Ferst Drive, ES&TAtlanta, GA 30332-0340Web: eas.gatech.edu

ES&T

L1114

Title:Hydrocarbon degradation by bacteria in coastal environment of northern Gulf of Mexico sediment after the Deepwater Horizon oil spill

Committee members: Joel Kostka, Martial Taillefert, Tom DiChristina, KarstenZengler(UCSD), Kuk-Jeong Chin (GSU)

Abstract: The objective of this dissertation research was to characterize sedimentary microbial populations that are active in degrading petroleum hydrocarbons that reach the seafloor during accidental oil spills. Whereas most previous work has investigated hydrocarbon-degrading microbial communities in sediments from seepenvironments that are regularlyexposed to high levels of oil, the focus of this study was on non-seep sediments that are not pre-exposed to high levels of petroleum.Anaerobic degradation of petroleum hydrocarbons coupled to sulfate reduction was studied in muddy sediments collected from nearby the Mississippi River delta. Sediment-freeenrichment cultures wereestablished and the metabolically active microorganisms that degrade model alkanes and polycyclic aromatic hydrocarbons were characterized. In particular, sulfate-reducing bacteria that degrade the 3 ring PAH, phenanthrene, were identified for the first time in marineenvironments. The biochemical mechanisms of phenanthrenedegradation under sulfate-reducing conditions were further investigated inenrichment cultures using a metagenomicapproach. The succession of microbial populations that mediate aerobic hydrocarbon degradation wasexamined in anexperiment conducted in situ at Pensacola Beach. Tarballsof Macondooil collected from the Deepwater Horizon discharge were buried in beach sands and hydrocarbon-degrading microbial communities were characterized over a 3 year period. Overall, this study provides fundamental science to improve predictions of the fate of petroleum hydrocarbons that are deposited in marine sediments after an oil spill.