Building a flagellum outside the bacterial cell

Trends Microbiol. 2014 Oct;22(10):566-72. doi: 10.1016/j.tim.2014.05.009. Epub 2014 Jun 24.


Flagella, the helical propellers that extend from the bacterial surface, are a paradigm for how complex molecular machines can be built outside the living cell. Their assembly requires ordered export of thousands of structural subunits across the cell membrane and this is achieved by a type III export machinery located at the flagellum base, after which subunits transit through a narrow channel at the core of the flagellum to reach the assembly site at the tip of the nascent structure, up to 20μm from the cell surface. Here we review recent findings that provide new insights into flagellar export and assembly, and a new and unanticipated mechanism for constant rate flagellum growth.

Keywords: bacterial flagellum; cell motility; chain mechanism; protein export; rotary nanomotor; type III secretion system.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Bacteria / metabolism*
  • Bacterial Proteins / metabolism*
  • Cell Membrane / metabolism
  • Flagella / metabolism*
  • Protein Transport


  • Bacterial Proteins