The polar Ras-like GTPase MglA activates type IV pilus via SgmX to enable twitching motility in <i>Myxococcus xanthus</i>
Romain Mercier, Sarah Bautista, Maëlle Delannoy, Margaux Gibert, Annick Guiseppi, Julien Herrou, Emilia M. F. Mauriello, Tâm Mignot
Abstract
Significance The type IV pilus (Tfp) is a multipurpose machine found on bacterial surfaces that works by cycles of synthesis/retraction of a pilin fiber. During surface (twitching) motility, the coordinated actions of multiple Tfps at the cell pole promotes single cells and synchronized group movements. Here, directly observing polar Tfp machines in action during motility of Myxococcus xanthus , we identified the mechanism underlying pole-specific Tfps activation. In this process, the Ras-like protein MglA targets a novel essential Tfp-activator, SgmX, to the pole, ensuring both the unipolar activation of Tfps and its switching to the opposite pole when cells reverse their movement. Thus, a dynamic cascade of polar activators regulates multicellular movements, a feature that is likely conserved in other twitching bacteria.