Andrew J Deak



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Bacterial infections that can no longer be treated by antibiotics because of bacterial mutations cause many infections and deaths each year. My research conducted aims to study how membrane fatty acid composition can affect bacterial susceptibility to antibiotics. Listeria monocytogenes, a gram-positive facultative anaerobe, is the bacterium that I am testing. Listeria has 80-90% branched-chain fatty acids (BCFAs) which allow membrane fluidity and sufficient protection against invaders. When Listeria is grown in the presence of butyrate, the BCFAs become straight-chain fatty acids (SCFAs) and make the once fluid membrane more rigid. We believe that this allows for easier antibiotic penetration of the phospholipid bilayer which lets the antibiotics affect cellular processes. By changing concentrations of butyrate I can therefore determine the minimum inhibitory concentrations of antibiotics for Listeria with different membrane fatty acid compositions. Moreover, as growth is a key factor in bacterial susceptibility to antibiotics. I also measure oxygen consumption rate in response to butyrate. Higher oxygen consumption rate is indicative of higher bacterial activity. Because oxygen consumption is carried out by protein complexes on the membrane, measuring oxygen consumption rate also reveal the effects of butyrate on cell membrane functionality.

Publication Date


Project Designation

Honors Thesis

Primary Advisor

Yvonne Y. Sun

Primary Advisor's Department



Stander Symposium project

Determining the Role of Membrane Fatty Acid Composition in Antibiotic Resistance