Biophysical Society Thematic Meeting | Ascona 2026

Mechanobiology of Infection

Wednesday Speaker Abstracts

MECHANICAL FORCES AS A TOOL TO DECIPHER BACTERIAL RESISTANCE AND DEATH Bart W. Hoogenboom University College London, London Centre for Nanotechnology, London, United Kingdom The Gram-negative bacterial cell envelope is a multilayer, composite structure, where particularly the outer membrane represents a formidable barrier to antimicrobials. With our work, we aim to address open questions about outer membrane architecture and about how its mechanical and structural integrity is affected by antimicrobial attack.Using molecular-resolution atomic force microscopy (AFM) on living bacteria, we have established that the outer membrane of E. coli is organised in near-static networks of outer membrane proteins, interspersed by phase separated, protein-depleted domains that are enriched in lipopolysaccharides (LPS). [1]When bacteria are exposed to last resort polymyxin antibiotics, large-scale disruption outer membrane disruption results, although the local protein superstructure appears to remain relatively unaffected. Surprisingly, such disruption depends on energy, and our experiments indicate that polymyxins effectively hijack the LPS synthesis machinery to stuff more LPS into the outer membrane than possible while sustaining outer membrane integrity. [2]Yet even when large chasms appear in the outer membrane, as, e.g., following treatment of E. coli with (immune) proteins from the complement system, this does not necessarily result in immediate death. For complement, we find that the outer membrane can sustain extensive poration and cracks before the overall mechanical integrity of the cell envelope is significantly degraded: This becomes apparent by an overall cell swelling and surface stiffening immediately before cell lysis, presumably since the cytoplasm starts to push more strongly against the outer membrane to ultimately overstretch the cytoplasmic membrane and thereby kill the cell. [3][1] Benn, G. et al., Proc. Natl. Acad. Sci. USA (2021). https://dx.doi.org/10.1073/pnas.2112237118[2] Borrelli, C., Douglas, E., et al., Nat. Microbiol. (2025). https://dx.doi.org/10.1038/s41564-025-02133-1[3] Benn, G., Bortolini, C. et al., EMBO J. (2024). https://dx.doi.org/10.1038/s44318-024-00266-3

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