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Type IV pili: dynamics, biophysics and functional consequences


The surfaces of many bacteria are decorated with long, exquisitely thin appendages called type IV pili (T4P), dynamic filaments that are rapidly polymerized and depolymerized from a pool of pilin subunits. Cycles of pilus extension, binding and retraction enable T4P to perform a phenomenally diverse array of functions, including twitching motility, DNA uptake and microcolony formation. On the basis of recent developments, a comprehensive understanding is emerging of the molecular architecture of the T4P machinery and the filament it builds, providing mechanistic insights into the assembly and retraction processes. Combined microbiological and biophysical approaches have revealed how T4P dynamics influence self-organization of bacteria, how bacteria respond to external stimuli to regulate T4P activity for directed movement, and the role of T4P retraction in surface sensing. In this Review, we discuss the T4P machine architecture and filament structure and present current molecular models for T4P dynamics, with a particular focus on recent insights into T4P retraction. We also discuss the functional consequences of T4P dynamics, which have important implications for bacterial lifestyle and pathogenesis.

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Fig. 1: Architecture of the type IV pilus machine.
Fig. 2: Structures of the type IV pilin subunit and pilus filaments and model for docking the major pilin subunit into the base of the growing pilus.
Fig. 3: General model for ATP-induced conformational changes in assembly and retraction ATPases.
Fig. 4: Models for ATPase-induced platform protein motions driving type IV pilus assembly.
Fig. 5: Retraction-dependent activities of piliated cells.


  1. 1.

    Hospenthal, M. K., Costa, T. R. D. & Waksman, G. A comprehensive guide to pilus biogenesis in Gram-negative bacteria. Nat. Rev. Microbiol. 15, 365–379 (2017).

    CAS  PubMed  Google Scholar 

  2. 2.

    Giltner, C. L., Nguyen, Y. & Burrows, L. L. Type IV pilin proteins: versatile molecular modules. Microbiol. Mol. Biol. Rev. 76, 740–772 (2012).

    CAS  PubMed  PubMed Central  Google Scholar 

  3. 3.

    Clausen, M., Koomey, M. & Maier, B. Dynamics of type IV pili is controlled by switching between multiple states. Biophys. J. 96, 1169–1177 (2009).

    CAS  PubMed  PubMed Central  Google Scholar 

  4. 4.

    Merz, A. J., So, M. & Sheetz, M. P. Pilus retraction powers bacterial twitching motility. Nature 407, 98–102 (2000).

    CAS  PubMed  Google Scholar 

  5. 5.

    Skerker, J. M. & Berg, H. C. Direct observation of extension and retraction of type IV pili. Proc. Natl Acad. Sci. USA 98, 6901–6904 (2001).

    CAS  PubMed  Google Scholar 

  6. 6.

    Maier, B. et al. Single pilus motor forces exceed 100 pN. Proc. Natl Acad. Sci. USA 99, 16012–16017 (2002).

    CAS  PubMed  Google Scholar 

  7. 7.

    Ellison, C. K. et al. Obstruction of pilus retraction stimulates bacterial surface sensing. Science 358, 535–538 (2017). This paper shows that surface binding by the T4P stops retraction, which signals production of the C. crescentus holdfast, and that retraction can be blocked by sterically obstructing passage of the pilus through the secretin channel.

    CAS  PubMed  PubMed Central  Google Scholar 

  8. 8.

    Biais, N., Ladoux, B., Higashi, D., So, M. & Sheetz, M. Cooperative retraction of bundled type IV pili enables nanonewton force generation. PLOS Biol. 6, e87 (2008).

    PubMed  PubMed Central  Google Scholar 

  9. 9.

    Ribbe, J., Baker, A. E., Euler, S., O’Toole, G. A. & Maier, B. Role of cyclic Di-GMP and exopolysaccharide in type IV pilus dynamics. J. Bacteriol. 199, e00859–16 (2017).

    CAS  PubMed  PubMed Central  Google Scholar 

  10. 10.

    Chamot-Rooke, J. et al. Posttranslational modification of pili upon cell contact triggers N. meningitidis dissemination. Science 331, 778–782 (2011).

    CAS  PubMed  Google Scholar 

  11. 11.

    Higashi, D. L. et al. Dynamics of Neisseria gonorrhoeae attachment: microcolony development, cortical plaque formation, and cytoprotection. Infect. Immun. 75, 4743–4753 (2007).

    CAS  PubMed  PubMed Central  Google Scholar 

  12. 12.

    Howie, H. L., Glogauer, M. & So, M. The N. gonorrhoeae type IV pilus stimulates mechanosensitive pathways and cytoprotection through a pilT-dependent mechanism. PLOS Biol. 3, e100 (2005).

    PubMed  PubMed Central  Google Scholar 

  13. 13.

    Holz, C. et al. Multiple pilus motors cooperate for persistent bacterial movement in two dimensions. Phys. Rev. Lett. 104, 178104 (2010).

    PubMed  Google Scholar 

  14. 14.

    Opitz, D. & Maier, B. Rapid cytoskeletal response of epithelial cells to force generation by type IV pili. PLOS ONE 6, e17088 (2011).

    CAS  PubMed  PubMed Central  Google Scholar 

  15. 15.

    Ellison, C. K. et al. Retraction of DNA-bound type IV competence pili initiates DNA uptake during natural transformation in Vibrio cholerae. Nat. Microbiol. 3, 773–780 (2018). This study shows that, during transformation, T4P bring extracellular DNA to the cell surface by retraction.

    CAS  PubMed  Google Scholar 

  16. 16.

    Clausen, M., Jakovljevic, V., Søgaard-Andersen, L. & Maier, B. High-force generation is a conserved property of type IV pilus systems. J. Bacteriol. 191, 4633–4638 (2009).

    CAS  PubMed  PubMed Central  Google Scholar 

  17. 17.

    Biais, N., Higashi, D. L., Brujic, J., So, M. & Sheetz, M. P. Force-dependent polymorphism in type IV pili reveals hidden epitopes. Proc. Natl Acad. Sci. USA 107, 11358–11363 (2010).

    CAS  PubMed  Google Scholar 

  18. 18.

    Parge, H. E. et al. Structure of the fibre-forming protein pilin at 2.6 A resolution. Nature 378, 32–38 (1995).

    CAS  PubMed  Google Scholar 

  19. 19.

    Craig, L. et al. Type IV pilin structure and assembly: X-ray and EM analyses of Vibrio cholerae toxin-coregulated pilus and Pseudomonas aeruginosa PAK pilin. Mol. Cell 11, 1139–1150 (2003).

    CAS  PubMed  Google Scholar 

  20. 20.

    Craig, L. et al. Type IV pilus structure by cryo-electron microscopy and crystallography: implications for pilus assembly and functions. Mol. Cell 23, 651–662 (2006).

    CAS  PubMed  Google Scholar 

  21. 21.

    Hartung, S. et al. Ultrahigh resolution and full-length pilin structures with insights for filament assembly, pathogenic functions, and vaccine potential. J. Biol. Chem. 286, 44254–44265 (2011).

    CAS  PubMed  PubMed Central  Google Scholar 

  22. 22.

    Reardon, P. N. & Mueller, K. T. Structure of the type IVa major pilin from the electrically conductive bacterial nanowires of Geobacter sulfurreducens. J. Biol. Chem. 288, 29260–29266 (2013).

    CAS  PubMed  PubMed Central  Google Scholar 

  23. 23.

    Strom, M. S. & Lory, S. Amino acid substitutions in pilin of Pseudomonas aeruginosa. Effect on leader peptide cleavage, amino-terminal methylation, and pilus assembly. J. Biol. Chem. 266, 1656–1664 (1991).

    CAS  PubMed  Google Scholar 

  24. 24.

    Horiuchi, T. & Komano, T. Mutational analysis of plasmid R64 thin pilus prepilin: the entire prepilin sequence is required for processing by type IV prepilin peptidase. J. Bacteriol. 180, 4613–4620 (1998).

    CAS  PubMed  PubMed Central  Google Scholar 

  25. 25.

    Aas, F. E. et al. Substitutions in the N-terminal alpha helical spine of Neisseria gonorrhoeae pilin affect Type IV pilus assembly, dynamics and associated functions. Mol. Microbiol. 63, 69–85 (2007).

    CAS  PubMed  Google Scholar 

  26. 26.

    Li, J., Egelman, E. H. & Craig, L. Structure of the Vibrio cholerae type IVb pilus and stability comparison with the Neisseria gonorrhoeae type IVa pilus. J. Mol. Biol. 418, 47–64 (2012).

    CAS  PubMed  PubMed Central  Google Scholar 

  27. 27.

    Nivaskumar, M. et al. Pseudopilin residue E5 is essential for recruitment by the type 2 secretion system assembly platform. Mol. Microbiol. 101, 924–941 (2016).

    CAS  PubMed  Google Scholar 

  28. 28.

    Egelman, E. H. Three-dimensional reconstruction of helical polymers. Arch. Biochem. Biophys. 581, 54–58 (2015).

    CAS  PubMed  PubMed Central  Google Scholar 

  29. 29.

    Smith, M. T. J. & Rubinstein, J. L. Beyond blob-ology. Science 345, 617–619 (2014).

    CAS  PubMed  Google Scholar 

  30. 30.

    Wang, F. et al. Cryoelectron microscopy reconstructions of the Pseudomonas aeruginosa and Neisseria gonorrhoeae type IV pili at sub-nanometer resolution. Structure 25, 1423–1435 (2017).

    CAS  PubMed  Google Scholar 

  31. 31.

    Kolappan, S. et al. Structure of the Neisseria meningitidis type IV pilus. Nat. Commun. 7, 13015 (2016).

    CAS  PubMed  PubMed Central  Google Scholar 

  32. 32.

    Beaussart, A. et al. Nanoscale adhesion forces of Pseudomonas aeruginosa type IV Pili. ACS Nano 8, 10723–10733 (2014).

    CAS  PubMed  PubMed Central  Google Scholar 

  33. 33.

    Brissac, T., Mikaty, G., Duménil, G., Coureuil, M. & Nassif, X. The meningococcal minor pilin PilX is responsible for type IV pilus conformational changes associated with signaling to endothelial cells. Infect. Immun. 80, 3297–3306 (2012).

    CAS  PubMed  PubMed Central  Google Scholar 

  34. 34.

    Pelicic, V. Type IV pili: e pluribus unum? Mol. Microbiol. 68, 827–837 (2008).

    CAS  PubMed  Google Scholar 

  35. 35.

    Ayers, M., Howell, P. L. & Burrows, L. L. Architecture of the type II secretion and type IV pilus machineries. Future Microbiol. 5, 1203–1218 (2010).

    CAS  PubMed  Google Scholar 

  36. 36.

    Ng, D. et al. The Vibrio cholerae minor pilin TcpB initiates assembly and retraction of the toxin-coregulated pilus. PLOS Pathog. 12, e1006109 (2016). The study demonstrates functional retraction in the absence of a retraction ATPase.

    PubMed  PubMed Central  Google Scholar 

  37. 37.

    Nguyen, Y. et al. Pseudomonas aeruginosa minor pilins prime type IVa pilus assembly and promote surface display of the PilY1 adhesin. J. Biol. Chem. 290, 601–611 (2015).

    CAS  PubMed  Google Scholar 

  38. 38.

    Giltner, C. L., Habash, M. & Burrows, L. L. Pseudomonas aeruginosa minor pilins are incorporated into type IV pili. J. Mol. Biol. 398, 444–461 (2010).

    CAS  PubMed  Google Scholar 

  39. 39.

    Helaine, S., Dyer, D. H., Nassif, X., Pelicic, V. & Forest, K. T. 3D structure/function analysis of PilX reveals how minor pilins can modulate the virulence properties of type IV pili. Proc. Natl Acad. Sci. USA 104, 15888–15893 (2007).

    CAS  PubMed  Google Scholar 

  40. 40.

    Chang, Y.-W. et al. Architecture of the Vibrio cholerae toxin-coregulated pilus machine revealed by electron cryotomography. Nat. Microbiol. 2, 16269 (2017).

    CAS  PubMed  PubMed Central  Google Scholar 

  41. 41.

    Chang, Y.-W. et al. Architecture of the type IVa pilus machine. Science 351, aad2001 (2016). The study provides a comprehensive view of the intact T4P machine in the bacterial envelope.

    PubMed  PubMed Central  Google Scholar 

  42. 42.

    Gold, V. A. M., Salzer, R., Averhoff, B. & Kühlbrandt, W. Structure of a type IV pilus machinery in the open and closed state. eLife 4, e07380 (2015).

    PubMed Central  Google Scholar 

  43. 43.

    Planet, P. J., Kachlany, S. C., DeSalle, R. & Figurski, D. H. Phylogeny of genes for secretion NTPases: identification of the widespread tadA subfamily and development of a diagnostic key for gene classification. Proc. Natl Acad. Sci. USA 98, 2503–2508 (2001).

    CAS  PubMed  Google Scholar 

  44. 44.

    Misic, A. M., Satyshur, K. A. & Forest, K. T. P. aeruginosa PilT structures with and without nucleotide reveal a dynamic type IV pilus retraction motor. J. Mol. Biol. 400, 1011–1021 (2010).

    CAS  PubMed  PubMed Central  Google Scholar 

  45. 45.

    McCallum, M., Tammam, S., Khan, A., Burrows, L. L. & Howell, P. L. The molecular mechanism of the type IVa pilus motors. Nat. Commun. 8, 15091 (2017). ADP and ATP-analogue-bound PilB structures provide the basis for a model of nucleotide turnover in sequential subunits, leading to clockwise ring conformational deformation in the assembly ATPase and anticlockwise deformation in the disassembly ATPase.

    CAS  PubMed  PubMed Central  Google Scholar 

  46. 46.

    Mancl, J. M., Black, W. P., Robinson, H., Yang, Z. & Schubot, F. D. Crystal structure of a type IV pilus assembly ATPase: insights into the molecular mechanism of PilB from thermus thermophilus. Structure 24, 1886–1897 (2016). This first structure of a T4P assembly ATPase reveals structural similarity in the motor mechanism to that of the retraction ATPases and highlights the two-fold symmetry of the oblong hexamer and likely force generation.

    CAS  PubMed  Google Scholar 

  47. 47.

    Satyshur, K. A. et al. Crystal structures of the pilus retraction motor PilT suggest large domain movements and subunit cooperation drive motility. Structure 15, 363–376 (2007).

    CAS  PubMed  PubMed Central  Google Scholar 

  48. 48.

    Collins, R. et al. Structural cycle of the Thermus thermophilus PilF ATPase: the powering of type IVa pilus assembly. Sci. Rep. 8, 14022 (2018). Single-particle electron microscopy reconstructions provide a model for how GSPII domains interact with the NTD and CTD in an assembly ATPase hexamer and highlight the ATP-dependent vertical shift of motor subunits, which likely have a role in pilus assembly.

    PubMed  PubMed Central  Google Scholar 

  49. 49.

    Solanki, V., Kapoor, S. & Thakur, K. G. Structural insights into the mechanism of Type IVa pilus extension and retraction ATPase motors. FEBS J. 285, 3402–3421 (2018).

    CAS  PubMed  Google Scholar 

  50. 50.

    Marathe, R. et al. Bacterial twitching motility is coordinated by a two-dimensional tug-of-war with directional memory. Nat. Commun. 5, 3759 (2014).

    CAS  PubMed  Google Scholar 

  51. 51.

    Finer, J. T., Simmons, R. M. & Spudich, J. A. Single myosin molecule mechanics: piconewton forces and nanometre steps. Nature 368, 113 (1994).

    CAS  PubMed  Google Scholar 

  52. 52.

    Seitz, P. & Blokesch, M. DNA-uptake machinery of naturally competent Vibrio cholerae. Proc. Natl Acad. Sci. USA 110, 17987–17992 (2013).

    CAS  PubMed  Google Scholar 

  53. 53.

    Wolfgang, M. et al. PilT mutations lead to simultaneous defects in competence for natural transformation and twitching motility in piliated Neisseria gonorrhoeae. Mol. Microbiol. 29, 321–330 (1998).

    CAS  PubMed  Google Scholar 

  54. 54.

    Chiang, P. et al. Functional role of conserved residues in the characteristic secretion NTPase motifs of the Pseudomonas aeruginosa type IV pilus motor proteins PilB, PilT and PilU. Microbiology 154, 114–126 (2008).

    CAS  PubMed  Google Scholar 

  55. 55.

    Wu, S. S., Wu, J. & Kaiser, D. The Myxococcus xanthus pilT locus is required for social gliding motility although pili are still produced. Mol. Microbiol. 23, 109–121 (1997).

    CAS  PubMed  Google Scholar 

  56. 56.

    Zöllner, R., Cronenberg, T. & Maier, B. Motor properties of PilT-independent type 4 pilus retraction in gonococci. J. Bacteriol. (2019).

    Article  PubMed  Google Scholar 

  57. 57.

    Kolappan, S., Ng, D., Yang, G., Harn, T. & Craig, L. Crystal structure of the minor pilin CofB, the initiator of CFA/III pilus assembly in enterotoxigenic Escherichia coli. J. Biol. Chem. 290, 25805–25818 (2015).

    CAS  PubMed  PubMed Central  Google Scholar 

  58. 58.

    Dietrich, M., Mollenkopf, H., So, M. & Friedrich, A. Pilin regulation in the pilT mutant of Neisseria gonorrhoeae strain MS11. FEMS Microbiol. Lett. 296, 248–256 (2009).

    CAS  PubMed  PubMed Central  Google Scholar 

  59. 59.

    Kilmury, S. L. N. & Burrows, L. L. Type IV pilins regulate their own expression via direct intramembrane interactions with the sensor kinase PilS. Proc. Natl Acad. Sci. USA 113, 6017–6022 (2016).

    CAS  PubMed  Google Scholar 

  60. 60.

    Persat, A., Inclan, Y. F., Engel, J. N., Stone, H. A. & Gitai, Z. Type IV pili mechanochemically regulate virulence factors in Pseudomonas aeruginosa. Proc. Natl Acad. Sci. USA 112, 7563–7568 (2015).

    CAS  PubMed  Google Scholar 

  61. 61.

    Inclan, Y. F. et al. A scaffold protein connects type IV pili with the Chp chemosensory system to mediate activation of virulence signaling in Pseudomonas aeruginosa. Mol. Microbiol. 101, 590–605 (2016).

    CAS  PubMed  PubMed Central  Google Scholar 

  62. 62.

    Lee, C. K. et al. Multigenerational memory and adaptive adhesion in early bacterial biofilm communities. Proc. Natl Acad. Sci. USA 115, 4471–4476 (2018).

    CAS  PubMed  Google Scholar 

  63. 63.

    O’Toole, G. A. & Wong, G. C. Sensational biofilms: surface sensing in bacteria. Curr. Opin. Microbiol. 30, 139–146 (2016).

    PubMed  PubMed Central  Google Scholar 

  64. 64.

    Schuergers, N. et al. Cyanobacteria use micro-optics to sense light direction. eLife 5, e12620 (2016).

    PubMed  PubMed Central  Google Scholar 

  65. 65.

    Nakane, D. & Nishizaka, T. Asymmetric distribution of type IV pili triggered by directional light in unicellular cyanobacteria. Proc. Natl Acad. Sci. USA 114, 6593–6598 (2017).

    CAS  PubMed  Google Scholar 

  66. 66.

    Oliveira, N. M., Foster, K. R. & Durham, W. M. Single-cell twitching chemotaxis in developing biofilms. Proc. Natl Acad. Sci. USA 113, 6532–6537 (2016).

    CAS  PubMed  Google Scholar 

  67. 67.

    Chau, R. M. W., Bhaya, D. & Huang, K. C. Emergent phototactic responses of cyanobacteria under complex light regimes. mBio 8, e02330–16 (2017).

    CAS  PubMed  PubMed Central  Google Scholar 

  68. 68.

    Wilde, A. & Mullineaux, C. W. Light-controlled motility in prokaryotes and the problem of directional light perception. FEMS Microbiol. Rev. 41, 900–922 (2017).

    CAS  PubMed  PubMed Central  Google Scholar 

  69. 69.

    Schuergers, N., Nürnberg, D. J., Wallner, T., Mullineaux, C. W. & Wilde, A. PilB localization correlates with the direction of twitching motility in the cyanobacterium Synechocystis sp. PCC 6803. Microbiology 161, 960–966 (2015).

    CAS  PubMed  Google Scholar 

  70. 70.

    Welker, A. et al. Molecular motors govern liquidlike ordering and fusion dynamics of bacterial colonies. Phys. Rev. Lett. 121, 118102 (2018). This study shows that tuning T4P motor activity modulates local structure and viscosity of bacterial microcolonies.

    CAS  PubMed  Google Scholar 

  71. 71.

    Bonazzi, D. et al. Intermittent pili-mediated forces fluidize Neisseria meningitidis aggregates promoting vascular colonization. Cell 174, 143–155 (2018). This study reveals that T4P retraction enhances colony fluidity and demonstrates important consequences of T4P retraction for vascular colonization.

    CAS  PubMed  Google Scholar 

  72. 72.

    Pönisch, W., Weber, C. A., Juckeland, G., Biais, N. & Zaburdaev, V. Multiscale modeling of bacterial colonies: how pili mediate the dynamics of single cells and cellular aggregates. New J. Phys. 19, 015003 (2017).

    Google Scholar 

  73. 73.

    Hockenberry, A. M., Hutchens, D. M., Agellon, A. & So, M. Attenuation of the type IV pilus retraction motor influences Neisseria gonorrhoeae social and infection behavior. mBio 7, e01994–16 (2016).

    CAS  PubMed  PubMed Central  Google Scholar 

  74. 74.

    Zöllner, R. et al. Type IV pilin post-translational modifications modulate materials properties of bacterial colonies. Biophys. J. (2019).

    Article  PubMed  Google Scholar 

  75. 75.

    Rotman, E. & Seifert, H. S. The genetics of Neisseria species. Annu. Rev. Genet. 48, 405–431 (2014).

    CAS  PubMed  Google Scholar 

  76. 76.

    Gelimson, A. et al. Multicellular self-organization of P. aeruginosa due to interactions with secreted trails. Phys. Rev. Lett. 117, 178102 (2016).

    PubMed  Google Scholar 

  77. 77.

    Kranz, W. T., Gelimson, A., Zhao, K., Wong, G. C. L. & Golestanian, R. Effective dynamics of microorganisms that interact with their own trail. Phys. Rev. Lett. 117, 038101 (2016).

    PubMed  Google Scholar 

  78. 78.

    Zhao, K. et al. Psl trails guide exploration and microcolony formation in Pseudomonas aeruginosa biofilms. Nature 497, 388–391 (2013).

    CAS  PubMed  PubMed Central  Google Scholar 

  79. 79.

    Hu, W. et al. Interplay between type IV pili activity and exopolysaccharides secretion controls motility patterns in single cells of Myxococcus xanthus. Sci. Rep. 6, 17790 (2016).

    CAS  PubMed  PubMed Central  Google Scholar 

  80. 80.

    Li, Y. et al. Extracellular polysaccharides mediate pilus retraction during social motility of Myxococcus xanthus. Proc. Natl Acad. Sci. USA 100, 5443–5448 (2003).

    CAS  PubMed  Google Scholar 

  81. 81.

    Gloag, E. S. et al. Self-organization of bacterial biofilms is facilitated by extracellular DNA. Proc. Natl Acad. Sci. USA 110, 11541–11546 (2013).

    CAS  PubMed  Google Scholar 

  82. 82.

    Zachreson, C. et al. Network patterns in exponentially growing two-dimensional biofilms. Phys. Rev. E 96, 042401 (2017).

    PubMed  Google Scholar 

  83. 83.

    Kim, W., Racimo, F., Schluter, J., Levy, S. B. & Foster, K. R. Importance of positioning for microbial evolution. Proc. Natl Acad. Sci. USA 111, E1639–E1647 (2014).

    CAS  PubMed  Google Scholar 

  84. 84.

    Smith, W. P. J. et al. Cell morphology drives spatial patterning in microbial communities. Proc. Natl Acad. Sci. USA 114, E280–E286 (2017).

    CAS  PubMed  Google Scholar 

  85. 85.

    Zöllner, R., Oldewurtel, E. R., Kouzel, N. & Maier, B. Phase and antigenic variation govern competition dynamics through positioning in bacterial colonies. Sci. Rep. 7, 12151 (2017).

    PubMed  PubMed Central  Google Scholar 

  86. 86.

    Dong, J. J. & Klumpp, S. Simulation of colony pattern formation under differential adhesion and cell proliferation. Soft Matter 14, 1908–1916 (2018).

    CAS  PubMed  Google Scholar 

  87. 87.

    Oldewurtel, E. R., Kouzel, N., Dewenter, L., Henseler, K. & Maier, B. Differential interaction forces govern bacterial sorting in early biofilms. eLife 4, e10811 (2015).

    PubMed  PubMed Central  Google Scholar 

  88. 88.

    Anyan, M. E. et al. Type IV pili interactions promote intercellular association and moderate swarming of Pseudomonas aeruginosa. Proc. Natl Acad. Sci. USA 111, 18013–18018 (2014).

    CAS  PubMed  Google Scholar 

  89. 89.

    Pönisch, W. et al. Pili mediated intercellular forces shape heterogeneous bacterial microcolonies prior to multicellular differentiation. Sci. Rep. 8, 16567 (2018).

    PubMed  PubMed Central  Google Scholar 

  90. 90.

    Harris, A. K. Is cell sorting caused by differences in the work of intercellular adhesion? A critique of the Steinberg hypothesis. J. Theor. Biol. 61, 267–285 (1976).

    CAS  PubMed  Google Scholar 

  91. 91.

    Klausen, M., Aaes-Jørgensen, A., Molin, S. & Tolker-Nielsen, T. Involvement of bacterial migration in the development of complex multicellular structures in Pseudomonas aeruginosa biofilms: biofilm mushrooms with a twitch. Mol. Microbiol. 50, 61–68 (2003).

    CAS  PubMed  Google Scholar 

  92. 92.

    Kaplan, J. B. et al. Low levels of β-lactam antibiotics induce extracellular DNA release and biofilm formation in Staphylococcus aureus. mBio 3, e00198–12 (2012).

    CAS  PubMed  PubMed Central  Google Scholar 

  93. 93.

    Matz, C., Bergfeld, T., Rice, S. A. & Kjelleberg, S. Microcolonies, quorum sensing and cytotoxicity determine the survival of Pseudomonas aeruginosa biofilms exposed to protozoan grazing. Environ. Microbiol. 6, 218–226 (2004).

    PubMed  Google Scholar 

  94. 94.

    Stingl, K., Müller, S., Scheidgen-Kleyboldt, G., Clausen, M. & Maier, B. Composite system mediates two-step DNA uptake into Helicobacter pylori. Proc. Natl Acad. Sci. USA 107, 1184–1189 (2010).

    PubMed  Google Scholar 

  95. 95.

    Gangel, H. et al. Concerted spatio-temporal dynamics of imported DNA and ComE DNA uptake protein during gonococcal transformation. PLOS Pathog. 10, e1004043 (2014).

    PubMed  PubMed Central  Google Scholar 

  96. 96.

    Hepp, C. & Maier, B. Bacterial translocation ratchets: shared physical principles with different molecular implementations: how bacterial secretion systems bias brownian motion for efficient translocation of macromolecules. Bioessays 39, 1700099 (2017).

    Google Scholar 

  97. 97.

    Hepp, C. & Maier, B. Kinetics of DNA uptake during transformation provide evidence for a translocation ratchet mechanism. Proc. Natl Acad. Sci. USA 113, 12467–12472 (2016).

    CAS  PubMed  Google Scholar 

  98. 98.

    Chen, I. & Dubnau, D. DNA uptake during bacterial transformation. Nat. Rev. Microbiol. 2, 241–249 (2004).

    CAS  PubMed  Google Scholar 

  99. 99.

    Cehovin, A. et al. Specific DNA recognition mediated by a type IV pilin. Proc. Natl Acad. Sci. USA 110, 3065–3070 (2013).

    CAS  PubMed  Google Scholar 

  100. 100.

    Laurenceau, R. et al. A type IV pilus mediates DNA binding during natural transformation in Streptococcus pneumoniae. PLOS Pathog. 9, e1003473 (2013).

    CAS  PubMed  PubMed Central  Google Scholar 

  101. 101.

    Chen, I., Provvedi, R. & Dubnau, D. A macromolecular complex formed by a pilin-like protein in competent Bacillus subtilis. J. Biol. Chem. 281, 21720–21727 (2006).

    CAS  PubMed  Google Scholar 

  102. 102.

    Obergfell, K. P. & Seifert, H. S. The pilin N-terminal domain maintains Neisseria gonorrhoeae transformation competence during pilus phase variation. PLOS Genet. 12, e1006069 (2016).

    PubMed  PubMed Central  Google Scholar 

  103. 103.

    Hamilton, H. L. & Dillard, J. P. Natural transformation of Neisseria gonorrhoeae: from DNA donation to homologous recombination: Natural transformation of Neisseria gonorrhoeae. Mol. Microbiol. 59, 376–385 (2006).

    CAS  PubMed  Google Scholar 

  104. 104.

    Seitz, P. et al. ComEA is essential for the transfer of external DNA into the periplasm in naturally transformable Vibrio cholerae cells. PLOS Genet. 10, e1004066 (2014).

    PubMed  PubMed Central  Google Scholar 

  105. 105.

    Peskin, C. S. & Oster, G. F. Force production by depolymerizing microtubules: load-velocity curves and run-pause statistics. Biophys. J. 69, 2268–2276 (1995).

    CAS  PubMed  PubMed Central  Google Scholar 

  106. 106.

    Sandkvist, M. Biology of type II secretion. Mol. Microbiol. 40, 271–283 (2001).

    CAS  PubMed  Google Scholar 

  107. 107.

    Hager, A. J. et al. Type IV pili-mediated secretion modulates Francisella virulence. Mol. Microbiol. 62, 227–237 (2006).

    CAS  PubMed  Google Scholar 

  108. 108.

    Kirn, T. J., Bose, N. & Taylor, R. K. Secretion of a soluble colonization factor by the TCP type 4 pilus biogenesis pathway in Vibrio cholerae. Mol. Microbiol. 49, 81–92 (2003).

    CAS  PubMed  Google Scholar 

  109. 109.

    Han, X., Kennan, R. M., Parker, D., Davies, J. K. & Rood, J. I. Type IV fimbrial biogenesis is required for protease secretion and natural transformation in Dichelobacter nodosus. J. Bacteriol. 189, 5022–5033 (2007).

    CAS  PubMed  PubMed Central  Google Scholar 

  110. 110.

    Yuen, A. S. W., Kolappan, S., Ng, D. & Craig, L. Structure and secretion of CofJ, a putative colonization factor of enterotoxigenic Escherichia coli. Mol. Microbiol. 90, 898–918 (2013).

    CAS  PubMed  Google Scholar 

  111. 111.

    Reichow, S. L. et al. The binding of cholera toxin to the periplasmic vestibule of the type II secretion channel. Channels (Austin) 5, 215–218 (2011).

    CAS  Google Scholar 

  112. 112.

    Thomassin, J.-L., Santos Moreno, J., Guilvout, I., Tran Van Nhieu, G. & Francetic, O. The trans-envelope architecture and function of the type 2 secretion system: new insights raising new questions. Mol. Microbiol. 105, 211–226 (2017).

    CAS  PubMed  Google Scholar 

  113. 113.

    McLaughlin, L. S., Haft, R. J. F. & Forest, K. T. Structural insights into the Type II secretion nanomachine. Curr. Opin. Struct. Biol. 22, 208–216 (2012).

    CAS  PubMed  PubMed Central  Google Scholar 

  114. 114.

    Korotkov, K. V., Sandkvist, M. & Hol, W. G. J. The type II secretion system: biogenesis, molecular architecture and mechanism. Nat. Rev. Microbiol. 10, 336–351 (2012).

    CAS  PubMed  PubMed Central  Google Scholar 

  115. 115.

    Maier, B. & Wong, G. C. L. How bacteria use type IV pili machinery on surfaces. Trends Microbiol. 23, 775–788 (2015).

    CAS  PubMed  Google Scholar 

  116. 116.

    Zaburdaev, V. et al. Uncovering the mechanism of trapping and cell orientation during Neisseria gonorrhoeae twitching motility. Biophys. J. 107, 1523–1531 (2014).

    CAS  PubMed  PubMed Central  Google Scholar 

  117. 117.

    Moffitt, J. R., Chemla, Y. R., Smith, S. B. & Bustamante, C. Recent advances in optical tweezers. Annu. Rev. Biochem. 77, 205–228 (2008).

    CAS  PubMed  Google Scholar 

  118. 118.

    Anderson, M. T., Dewenter, L., Maier, B. & Seifert, H. S. Seminal plasma initiates a Neisseria gonorrhoeae transmission state. mBio 5, e01004–13 (2014).

    PubMed  PubMed Central  Google Scholar 

  119. 119.

    Sabass, B., Koch, M. D., Liu, G., Stone, H. A. & Shaevitz, J. W. Force generation by groups of migrating bacteria. Proc. Natl Acad. Sci. USA 114, 7266–7271 (2017).

    CAS  PubMed  Google Scholar 

  120. 120.

    Schwarz, U. S. & Soiné, J. R. D. Traction force microscopy on soft elastic substrates: a guide to recent computational advances. Biochim. Biophys. Acta 1853, 3095–3104 (2015).

    CAS  PubMed  Google Scholar 

  121. 121.

    Sabass, B., Gardel, M. L., Waterman, C. M. & Schwarz, U. S. High resolution traction force microscopy based on experimental and computational advances. Biophys. J. 94, 207–220 (2008).

    CAS  PubMed  Google Scholar 

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L.C. is supported by a Discovery Grant from the Natural Sciences and Engineering Research Council and a VPR RPEG grant from Simon Fraser University. B.M. is supported by the Deutsche Forschungsgemeinschaft through grant MA3898. K.T.F. is supported by a Vilas Associate Award from the University of Wisconsin–Madison Office of the Vice Chancellor for Research and Graduate Education.

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Nature Reviews Microbiology thanks G. Duménil and other anonymous reviewer(s) for their contribution to the peer review of this work.

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The authors contributed equally to all aspects of the article.

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Correspondence to Lisa Craig or Katrina T. Forest or Berenike Maier.

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Supplementary Information



The conserved hydrophobic amino-terminal half of the extended α-helix of the major and minor pilins. α1N anchors the pilin subunits in the inner membrane before pilus assembly and anchors the pilin globular domains in the intact pilus filament.

Subtomogram averaging

A method that enables low-resolution 3D imaging of intact type IV pilus machines within the bacterial envelope by selecting and averaging multiple volumes within a full tomogram (subtomograms) that each represent the same protein, revealing the electron density of individual components.

PAS-like domain

The PAS domain is an α/β fold, named for the three proteins in which it was first identified. The motor ATPase amino-terminal domains bear structural similarity to the PAS domain.

Correlated random walks

At short timescales, movements are directed, but at long timescales, the steps occur independent of the direction of the previous step.

Tug of war

As the rate of the pilus detachment from the surface increases with force, local clustering of pili reduces detachment, and bacteria move preferentially in the direction where the pilus cluster is located.


Aggregates of bacteria that form on host tissues and synthetic substrates and are precursors to biofilms.

Rupture force

The mean force at which the bond between type IV pili from adjacent cells ruptures.


A coordinated motility mechanism on semisolid surfaces driven by flagella.

Range expansion assays

Assays in which labelled competing bacteria are mixed in liquid and inoculated onto an agar plate and subsequent microscopy enables quantification of competitors as a function of time.

Phase variation

The reversible change between defined expression states of genes mediated by invertible DNA segments, changes in the stretches of homopolymeric nucleotides, short tandem repeats or other mechanisms.


A short filament formed within the periplasm as part of the type II secretion system, so named because of structural and functional homologies to the type IV pilus.

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Craig, L., Forest, K.T. & Maier, B. Type IV pili: dynamics, biophysics and functional consequences. Nat Rev Microbiol 17, 429–440 (2019).

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