Journal
MBIO
Volume 13, Issue 1, Pages -Publisher
AMER SOC MICROBIOLOGY
DOI: 10.1128/mbio.03754-21
Keywords
type 4 pili; force; PilY1; von Willebrand A domain; surface sensing; c-di-GMP
Categories
Funding
- NIH [R37 AI83256, R01 AI43730]
- NSF Graduate Research Fellowship [DGE-1650604, DGE-2034835]
- BioMT through NIH NIGMS [P20-GM113132]
- Excellence of Science-EOS program [30550343]
- European Research Council (ERC) under the European Union [693630]
- National Fund for Scientific Research (FNRS)
- COBRE/NIGMS [5 P20 GM130454-02]
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Pseudomonas aeruginosa uses force-induced changes mediated by the PilY1 protein to sense surfaces and regulate biofilm formation. The study provides insights into the mechanosensing mechanism of type IV pili and its role in surface colonization strategies.
During biofilm formation, the opportunistic pathogen Pseudomonas aeruginosa uses its type IV pili (TFP) to sense a surface, eliciting increased second-messenger production and regulating target pathways required to adapt to a surface lifestyle. The mechanisms whereby TFP detect surface contact are still poorly understood, although mechanosensing is often invoked, with few data supporting this claim. Using a combination of molecular genetics and single-cell analysis, with biophysical, biochemical, and genomics techniques, we show that force-induced changes mediated by the von Willebrand A (vWA) domain-containing, TFP tip-associated protein PilY1 are required for surface sensing. Atomic force microscopy shows that TFP/PilY1 can undergo force-induced, sustained conformational changes akin to those observed for mechanosensitive proteins like titin. We show that mutation of a single cysteine residue in the vWA domain of PilY1 results in modestly lower surface adhesion forces, reduced sustained conformational changes, and increased nanospring-like properties, as well as reduced c-di-GMP signaling and biofilm formation. Mutating this cysteine has allowed us to genetically separate a role for TFP in twitching motility from surface-sensing signaling. The conservation of this Cys residue in all P. aeruginosa PA14 strains and its absence in the similar to 720 sequenced strains of P. aeruginosa PAO1 may contribute to explaining the observed differences in surface colonization strategies observed for PA14 versus PAO1. IMPORTANCE Most bacteria live on abiotic and biotic surfaces in surface-attached communities known as biofilms. Surface sensing and increased levels of the second-messenger molecule c-di-GMP are crucial to the transition from planktonic to biofilm growth. The mechanism(s) underlying TFP-mediated surface detection that triggers this c-di-GMP signaling cascade is unclear. Here, we provide key insight into this question; we show that the eukaryote-like vWA domain of the TFP tip-associated protein PilY1 responds to mechanical force, which in turn drives the production of a key second messenger needed to regulate surface behaviors. Our studies highlight a potential mechanism that may account for differing surface colonization strategies.
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