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Bactericidal membrane attack complex formation initiates at the new pole of E. coli
Marije F L van 't Wout1, Fabian Hauser2, Philippa I P Holzapfel1
1Department of Medical Microbiology, University Medical Center Utrecht, Utrecht University, Utrecht, The Netherlands.
EMBO Reports
|December 9, 2025
Summary
The bacterial complement system forms Membrane Attack Complex (MAC) pores that damage Gram-negative bacteria. These pores preferentially insert into new bacterial poles, causing inner membrane damage and halting cell division.
Area of Science:
- Microbiology
- Immunology
- Cell Biology
Background:
- Human immune protection against bacteria relies on the complement system.
- The Membrane Attack Complex (MAC) forms pores in Gram-negative bacteria, causing cell death.
- Inner membrane damage is crucial for MAC-mediated bacterial death, but the precise mechanism is unknown.
Purpose of the Study:
- To investigate if the bacterial cell envelope has vulnerable sites for MAC pore insertion.
- To determine the localization and timing of MAC pore formation on E. coli.
Main Methods:
- Fluorescence microscopy was used to track MAC pore localization on E. coli over time.
- Localization of MAC components (C8, C9, C3b) was analyzed.
Main Results:
- MAC deposition preferentially initiates at the new bacterial pole.
- Inner membrane damage and halted bacterial division were observed following MAC pore formation.
- C8 and C9 localized to new poles, while C3b distributed randomly, suggesting early MAC formation steps dictate localization.
Conclusions:
- The new bacterial pole is a vulnerable site for MAC pore insertion.
- Preferential MAC localization at the new pole triggers inner membrane damage and inhibits bacterial division.
- These findings offer insights into host-pathogen interactions and complement-mediated bacterial killing.
Keywords:
Complement SystemFluorescence MicroscopyGram-negative BacteriaImage AnalysisMembrane Attack ComplexMore Related Videos
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