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Researchers investigated how bacterial type IV pili maintain both mechanical strength and functional flexibility under force. Using cryo-electron microscopy at 2.8 Angstrom resolution, molecular dynamics simulations across six bacterial species, and optical tweezers experiments, they identified a conserved electrostatic network that allows the pili to tune their elasticity under tensile load. When they experimentally altered these interactions to create overly rigid pili, the structures assembled correctly but could no longer support normal twitching motility, revealing a fundamental trade-off between mechanical resilience and adaptive flexibility.
Why it matters
This work reveals design principles for biological structures that must balance strength with flexibility, which could inform the engineering of synthetic materials and molecular machines. Understanding how bacteria control pilus mechanics may also enable new approaches to disrupting bacterial motility and biofilm formation in pathogenic species like Pseudomonas aeruginosa.
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⚠️ Preprint – Noch nicht peer-reviewed
Dieser Artikel wurde noch nicht von unabhängigen Experten begutachtet. Die Ergebnisse sind vorläufig und sollten mit Vorsicht interpretiert werden.
Biological machines operate under mechanical load, requiring architectures that simultaneously resist force and remain functionally dynamic. Type IV pili (T4P) are bacterial filaments that experience large tensile forces during motor-driven retraction. Here, we combine cryo-electron microscopy, molecular dynamics simulations, optical tweezers, and functional analyses to define the structural basis of T4P mechanical adaptation. We determined a 2.8 [A] cryo-EM structure of the Pseudomonas aeruginosa T4P and integrated it with comparative all-atom simulations across six bacterial strains to identify a conserved force-bearing electrostatic network. Simulations predicted that this network tunes filament elasticity under load, a finding validated by single-filament force spectroscopy. Rewiring these interactions experimentally produced hyper-rigid pili that assembled normally but exhibited impaired twitching motility. Together, our findings uncover a structural trade-off between force-resistant architecture and reversible supramolecular adaptability.