Examining the Biophysical Properties of the Inner Membrane of Gram-Negative ESKAPE Pathogens

The World Health Organization has identified multidrug-resistant bacteria as a serious global health threat. Gram-negative bacteria are particularly prone to antibiotic resistance, and their high rate of antibiotic resistance has been suggested to be related to the complex structure of their cell membrane. The outer membrane of Gram-negative bacteria contains lipopolysaccharides that protect the bacteria against threats such as antibiotics, while the inner membrane houses 20-30% of the bacterial cellular proteins. Given the cell membrane's critical role in bacterial survival, antibiotics targeting the cell membrane have been proposed to combat bacterial infections. However, a deeper understanding of the biophysical properties of the bacterial cell membrane is crucial to developing effective and specific antibiotics. In this study, Martini coarse-grain molecular dynamics simulations were used to investigate the interplay between membrane composition and biophysical properties of the inner membrane across four pathogenic bacterial species: Klebsiella pneumoniae, Pseudomonas aeruginosa, Enterobacter cloacae, and Escherichia coli. The simulations indicate the impact of species-specific membrane composition on the overall membrane properties. Specifically, the cardiolipin concentration in the inner membrane is a key factor influencing the membrane features. Model membranes with varying concentrations of bacterial lipids (phosphatidylglycerol, phosphatidylethanolamine, and cardiolipin) further support the significant role of cardiolipin in determining the membrane biophysical properties. The bacterial inner membrane models developed in this work pave the way for future simulations of bacterial membrane proteins and for simulations investigating novel strategies aimed at disrupting the bacterial membrane to treat antibiotic-resistant infections.