Doctoral defence in Biology - Sean Michael Scully

Ph.D. student: Sean Michael Scully

Dissertation title: Amino Acid and Related Catabolism of Thermoanaerobacter Species

Opponents: 
Dr. Jessica Adams, Scientist at Aberystwyth University, Wales
Dr. Pauline Vannier, Research Scientist at Matis ohf.

Department coordinator: Dr. Guðmundur Óli Hreggviðsson, Professor at the Faculty of Life and Environmental Sciences at the University of Iceland and Strategic scientist at Matis ohf.

Advisor: Dr. Jóhann Örlygsson, Professor at the University of Akureyri

Also a member of the doctoral committee: Dr. Ólafur Friðjónsson, Research group leader at Matis ohf.

Chair of Ceremony: Dr. Snæbjörn Pálsson, Professor and Vice Head of the Faculty of Life and Environmental Sciences at the University of Iceland

Abstract:

The protein and amino acid metabolism of thermophilic bacteria has been a neglected aspect of their physiology despite their biotechnological potential. Under anaerobic conditions, many proteogenic amino acids require the presence of an electron scavenging system in order to effectively remove reducing equivalences and make the overall reaction thermodynamically favorable. Thermoanaerobacter and Caldanaerobacter strains cultivated on branched-chain amino acids (BCAAs) in the presence of methanogen or with thiosulfate resulted in production of their corresponding branched-chain fatty acid (BCFA) or a mixture including the BCFAs and the corresponding branched-chain alcohol (BCOH), respectively. Thus, these electron scavenging systems reveal a difference in the electron flow resulting in different fermentation products. Studies involving the entire genus reveal differences in the amino acid utilization patterns and the degree to which strains are proteolytic although the ability to degrade BCAAs to their corresponding BCFA and BCOH appears to be a universal feature although the ratio of BCOH/BCFA varies widely. Initially, the pathway responsible for BCOH formation was unclear; subsequent investigations using 13C-labeled BCAA, as well as exogenously added fatty acids (e.g. acetate, 3-methyl-1-butyrate) demonstrated that some Thermoanaerobacter and Caldanaerobacter strains could use the fatty acids as electron acceptors and convert them to their corresponding alcohols. Subsequent work demonstrates that Thermoanaerobacter pseudoethanolicus and Thermoanaerobacter strain AK85 are useful agents for the biotransformation of C2-C6 fatty acids to their corresponding alcohols in the presence of an electron donor.

About the doctoral candidate:

Sean Scully was born in United States where he previously studied chemistry and biology at the University of Toledo and moved to Iceland in 2008. He obtained a B.Sc. degree in biotechnology and MSc in Natural Resource Science at the University of Akureyri. He lives in northern Iceland with his family where he enjoys spending time outdoors.

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