Computational Study of Bacterial Membrane Disruption by Cationic Biocides: Structural Basis for Water Pore Formation

The development of biocides as disinfectants that do not induce bacterial resistance is crucial to health care since hospital-acquired infections afflict millions of patients every year. Recent experimental studies of a class of cationic biocides based on the phenylene ethynylene backbone, known as OPEs, have revealed that their biocidal activity is accompanied by strong morphology changes to bacterial cell membranes. In vitro studies of bacterial membrane mimics have shown changes to the lipid phase that are dependent on the length and orientation of the cationic moieties on the backbone. This study uses classical molecular dynamics to conduct a comprehensive survey of how oligomers with different chemical structures interact with each other and with a bacterial cell membrane mimic. In particular, the ability of OPEs to disrupt membrane structure is studied as a function of the length of the biocides and the orientation of their cationic moieties along the backbone of the molecule. The simulation results show that the structure of OPEs radically affects their interactions with a lipid bilayer. Biocides with branched cationic groups form trans-membrane water pores regardless of their backbone length, while only 1-1.5 nm of membrane thinning is observed with biocides with cationic groups on their terminal ends. The molecular dynamics simulations provide mechanistic details at the molecular level of the interaction of these biocidal oligomers and the lipid bilayer and corroborate experimental findings regarding observed differences in membrane disruption by OPEs with different chemical structures.