In vitro and in silico investigations of changes in bacterial cell membrane dynamics due to polyunsaturated fatty acid (PUFA) modifications

Project Summary/Abstract Bacterial responses to fatty acids include, but are not limited to, degradation for metabolic gain, modification of membrane lipids, alteration of protein function and regulation of gene expression. Vibrio species exhibit significant diversity with regard to the machinery known to participate in the uptake and incorporation of fatty

acids into their membranes. Both aquatic and host niches occupied by Vibrio are rife with various free fatty acids and fatty acid-containing lipids. The roles of fatty acids in the survival and pathogenesis of bacteria have begun to emerge and are expected to expand significantly. Compared to the import mechanisms of minerals (e.g., iron)

and sugars (e.g., lactose), the process and significance of scavenging and handling fatty acids is punctuated with gaps in knowledge. Gaining a better understanding of how microbes harness environment-specific resources will shed light on several themes of pathogenesis, such as environmental persistence, transmission to humans, and course of

disease. The varied abilities of bacteria to recognize, uptake and utilize lipid molecules from their environment certainly represents a worthwhile research endeavor. It is hypothesized that Vibrio cholerae undergoes significant structural modifications to its membrane phospholipids depending on the exogenously available

polyunsaturated fatty acids (PUFAs), and that these alterations affect membrane permeability sufficient to change the susceptibility to membrane active antimicrobials. The proposed project seeks to advance a specific mission of the NIGMS: to increase our understanding of biological processes and lay the foundation for advances

in disease diagnosis, treatment, and prevention. Accordingly, the research aims are to i) interrogate the nature and degree of polyunsaturated fatty acid (PUFA) incorporation into membrane phospholipids and ii) examine the altered membrane dynamics and antibiotic susceptibility conferred by exogenously acquired PUFAs.

Bioanalytical methodologies (thin-layer chromatography and UPLC/MS) will quantify and structurally characterize exogenous PUFA-mediated phospholipid modifications. Interrogation of membrane permeability will be performed in vitro using established dye-based assays and in silico with atomistic modeling and simulation

analyses. Collectively, the data will lay the foundation for deciphering a versatile pathway in Gram-negative bacteria by defining PUFA assimilation capability and its impact on membrane permeability, a critical cellular attribute that must be characterized in the interest of developing strategies to combat infection.

The results of these studies should contribute to our current understanding of how and why bacteria have evolved to utilize a variety of exogenous lipid molecules, thus providing insight into their survival both outside and within the host, as well as unlocking pathways vulnerable to antimicrobial attack.