Giles, David K.
Bell, Rebekah; Carver, Ethan
University of Tennessee at Chattanooga
Place of Publication
AIM: Acinetobacter baumannii is a ubiquitous gram-negative bacterium found on a variety of surfaces that include skin, hair, and soil. Some gram-negative bacteria like A. baumannii have the ability to acquire and incorporate fatty acids into their phospholipid membranes. Known as ‘Iraqibacter,’ A. baumannii has emerged as a significant cause of nosocomial infections in the United States and abroad. This study was designed to determine whether structural alterations occur in A. baumannii upon exposure to a wide range of polyunsaturated fatty acids (PUFAs) as well as the significance of this phenomenon in terms of survival and resistance to stress. Thin layer chromatography of isolated phospholipids indicated phospholipid profile variation depending on the exogenous PUFA supplied. To assess the incorporation of exogenous fatty acids with A. baumannii phospholipids, isolated lipids were analyzed by ultra-performance liquid chromatography/mass spectrometry (UPLC/MS). Membrane permeability was assessed with a crystal violet hydrophobic compound uptake assay. An assay for biofilm formation was performed to indicate the production of biofilms among bacterial growth in the presence of each fatty acid. To observe additional phenotypic responses, environmental stresses such as hydrogen peroxide, antimicrobial peptide, and antibiotic pressures were assayed. The fatty acids affected membrane permeability, as determined by a hydrophobic compound uptake test. At least a 20% range of uptake was observed between the PUFAs examined. Bacterial growth in the presence of each PUFA caused an increase in biofilm production. As expected, numerous unique phospholipid species were identified and were bioinformatically predicted to contain the exogenously supplied PUFA as one of their acyl chains. While no differences in minimum inhibitory concentrations were observed with peroxide and beta-lactam antibiotic stresses, sensitivity of A. baumannii to two different antimicrobial peptides, colistin and polymyxin B, increased following growth in several of the PUFAs, with arachidonic acid displaying the highest inhibition. Since cationic antimicrobial peptides are believed to interact with bacterial lipid membranes for eventual pore formation, these results implicate exogenous fatty acids as modification moieties that may impact resistance to environmental stresses.
Funding for my departmental honors thesis came from the Provost Student Research Award and the UC Foundation Grote Fund. In addition, Daniel Shults and Dr. Steven Symes from the Department of Chemistry played an integral role in processing and analyzing data for UPLC-MS.
B. S.; An honors thesis submitted to the faculty of the University of Tennessee at Chattanooga in partial fulfillment of the requirements of the degree of Bachelor of Science.
Drug resistance in microorganisms
Munir, Saba A., "The uptake and incorporation of exogenous fatty acids confer phenotypic advantages to acinetobacter baumannii" (2015). Honors Theses.