Type IV pili - A numbers game

Type IV pili are long polymers located on the surface of a wide variety of bacterial cells, including the pathogen Neisseria meningitidis. They are responsible for a diverse range of functions, including adhesion, motility and natural transformation. In this issue of The EMBO Journal, Imhaus and Duménil show that two minor pilins, PilX and PilV, exert some of their effects by changing mean surface pilus number and that this modulates different pilus-dependent functions. In contrast to previous reports suggesting a qualitative role, minor pilins PilV and PilX exert their functions in a quantitative manner, regulating pili number at the cell surface. © 2014 The Authors. Published under the terms of the CC BY 4.0 license.