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Advisory Committee Chair

Asim K Bej

Advisory Committee Members

Jason Linville

Thane Wibbels

Document Type

Thesis

Date of Award

2013

Degree Name by School

Master of Science (MS) College of Arts and Sciences

Abstract

We investigated the changes of the bacterial community to treatment of Mississippi Canyon Macondo oil (MC252) in Gulf of Mexico (GoM) coastal sediment microcosms collected from Bayou La Batre, Dauphin Island, Petit Bois Island, and Perdido Pass. We utilized molecular methods by targeting the V3-V5 region of the16S rRNA gene from metacommunity DNA through culture-dependent and culture-independent (Bacterial Tag-encoded FLX Amplified Pyrosequencing; bTEFAP) methodologies and downstream bioinformatics tools. Through bTEFAP, we generated a total of 11,338 (Bayou La Batre) and 38,104 (Dauphin Island, Petit Bois Island, and Perdido Pass) reads. After quality-based trimming, a total of 8,430 (Bayou La Batre) and 36,520 (Dauphin Island, Petit Bois Island, and Perdido Pass) quality reads remained. Following quality checking, analyses of the bTEFAP data determined that the microbial assemblages of all 4 locations showed changes to the oil treatment. The phyla Proteobacteria, Bacteroidetes, and Firmicutes all increased with treatment of oil and thus may play an important role in biodegradation and bioremediation of oil. In particular, within the phylum Proteobacteria, the class Gammaproteobacteria appeared to be the dominant bacterial taxon in the oil treated samples. Moreover, we were able to identify microbial taxa that associated with early response, early transient response, and late response in relation to oil treatment. In order to investigate the presence of biodegradative genes, we conducted PCR to detect the presence of biodegradative genes in all 4 sample sites. Our results showed the amplification of biodegradative genes such as alkane hydroxylase (alkB870G), catechol 2,3 dioxygenase (C23DO, and Cat2,3 1a) and biphenyl dioxygenase (bphA1) in oil treated sediments. Futhermore, we isolated a consortium of bacterial isolates: Exiguobacterium, Pseudoalteromonas, Halomonas and Dyadobacter that carried hydrocarbon-degrading genes such as alkane hydroxylase (Rh-alkB1, Rh-alkB2, and alkB870G), the ISP alpha subunit of naphthalene dioxygenase (ndoB), C23DO, Cat2,3 1a, and bphA1. Collectively, our results indicated that the indigenous bacterial communities in all 4 different sampling locations responded quickly to the addition of MC252 oil and as a result, the bacterial community structure altered selectively for hydrocarbonocalstic taxa that possess biodegradation activity of oil in the GoM ecosystem.

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