Membrane-Active Antibiotics Affect Domains in Bacterial\nMembranes as the First Step of Their Activity

The need to combat\nantimicrobial resistance is becoming more and\nmore pressing. Here we investigate the working mechanism of a small\ncationic agent, <i>N</i>-alkylamide 3d, by conventional\nand high-speed atomic force microscopy. We show that <i>N</i>-alkylamide 3d interacts with the membrane of <i>Staphylococcus\naureus</i>, where it changes the organization and dynamics of\nlipid domains. After this initial step, supramolecular structures\nof the antimicrobial agent attach on top of the affected membrane\ngradually, covering it entirely. These results demonstrate that lateral\ndomains in the bacterial membranes might be affected by small antimicrobial\nagents more often than anticipated. At the same time, we show a new\ndual-step activity of <i>N</i>-alkylamide 3d that not only\ndestroys the lateral membrane organization but also effectively covers\nthe whole membrane with aggregates. This final step could render the\nmembrane inaccessible from the outside and possibly prevent signaling\nand waste disposal of living bacteria.