Effect of Fatty Acid Compounds in Persister Formation of Escherichia coli

Persisters are a dormant subpopulation of bacterial community that exhibits significant tolerance to antibiotics without genetic modification, because slow cell division and protein synthesis in the dormant state results in insensitivity to antibiotics targeting these steps. Once the level of antibiotics drops, persister cells revive by becoming active cells. Thus, persister cell formation of bacteria is problematic in controlling infectious diseases. Little is known about the mechanisms of persister formation and revival, and thereby there is few effective means to eradicate persister cells. In this study, we investigate different types of fatty acid compounds to see how they affect the survival of Escherichia coli under antibiotic treatment. Short chain fatty acids including butyric acid, propionic acids, and valeric acids are known for antibacterial activity by damaging cell membranes which is a different mechanism from common antibiotics. We observed that high concentration (20 mM) of fatty acids arrests cell growth and decrease the level of pH in the E. coli culture, while low concentration (<5 mM) of fatty acids does not affect cell growth but has a less effect in pH decrease. When the E. coli culture was treated with ampicillin (100 µg/mL) along with short chain fatty acids both high and low concentrations, persister cell formation was increased significantly similar to the cell survival level of un-treated E. coli. We are working on figuring out how cells increase their survival under the presence of both antibiotic and fatty acid antibacterial. We will further assess effect of fatty acids on pathogenic bacteria such as enterohemorrhagic E. coli and Pseudomonas aeruginosa. This study opens the development of novel strategies for combating pathogenic bacteria and controlling infectious diseases.