Polymyxin B lethality requires energy-dependent outer membrane disruption

Borrelli, C.; Douglas, E. J. A.; Riley, S. M. A.; Lemonidi, A. E.; Larrouy-Maumus, G. B.; Lu, W.-J.; Bonev, B. B.; Edwards, A. M.; Hoogenboom, B. W.

doi:10.1101/2025.04.16.649083

bioRxiv · 10.1101/2025.04.16.649083

Polymyxin B lethality requires energy-dependent outer membrane disruption

Borrelli, C.·Douglas, E. J. A.·Riley, S. M. A.·Lemonidi, A. E.·Larrouy-Maumus, G. B.·Lu, W.-J.·Bonev, B. B.·Edwards, A. M.·Hoogenboom, B. W.

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Abstract

Polymyxin antibiotics target lipopolysaccharide (LPS) in both membranes of the bacterial cell envelope, leading to bacterial killing through a mechanism that remains poorly understood. Here, we demonstrate that metabolic activity is essential for polymyxin lethality and leverage this insight to determine its mode of action. Polymyxin B (PmB) efficiently killed exponential phase E. coli but was unable to eliminate stationary phase cells unless a carbon source was available. Antibiotic lethality correlated with surface protrusions, LPS loss, and a significant reduction in outer membrane (OM) barrier function, processes that required LPS synthesis and transport. While the energy-dependent OM disruption was not directly lethal, it facilitated PmB access to the inner membrane (IM), which the antibiotic permeabilised in an energy-independent manner, leading to cell death. Finally, we show that the polymyxin resistance determinant MCR-1 prevents PmB-mediated LPS loss and OM protrusions and thereby renders the antibiotic ineffective.

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Borrelli, C., Douglas, E. J. A., Riley, S. M. A., Lemonidi, A. E., Larrouy-Maumus, G. B., Lu, W.-J., Bonev, B. B., Edwards, A. M., Hoogenboom, B. W.. 2025-04-16. Polymyxin B lethality requires energy-dependent outer membrane disruption. https://doi.org/10.1101/2025.04.16.649083

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