Abstract
Type IV pili (Tfp) are highly conserved macromolecular structures that fulfill diverse cellular functions, such as adhesion to host cells, the import of extracellular DNA, kin recognition, and cell motility (twitching). Outstandingly, twitching motility enables a poorly understood process by which highly coordinated groups of hundreds of cells move in cooperative manner, providing a basis for multicellular behaviors, such as biofilm formation. In the social bacteria Myxococcus xanthus, we know that twitching motility is under the dependence of the small GTPase MglA, but the underlying molecular mechanisms remain elusive. Here we show that MglA complexed to GTP recruits a newly characterized Tfp regulator, termed SgmX, to activate Tfp machines at the bacterial cell pole. This mechanism also ensures spatial regulation of Tfp, explaining how MglA switching provokes directional reversals. This discovery paves the way to elucidate how polar Tfp machines are regulated to coordinate multicellular movements, a conserved feature in twitching bacteria.
Highlights
Type IV pili (Tfp) are highly conserved macromolecular structures that fulfill diverse cellular functions, such as adhesion to host cells, the import of extracellular DNA, kin recognition, and cell motility
Twitching motility leads to the remarkable formation of coordinated cell groups, in which hundreds of cells move in a cooperative manner similar to swarming motility in flagellated bacteria [4, 5]
Two main features emerged from our observations: 1) labeled PilAD71C pilin formed a specific fluorescence enrichment cluster at the active cell pole (Fig. 1 A–C, arrow), absent in a strain lacking the variant pilAD71C (SI Appendix, Fig. S1B); 2) in motile cells, dynamics of the pili filaments could be directly observed at the leading cell pole, propelling the cell as they extended and retracted (Fig. 1A2 and Movie S1) in a similar fashion as observed in Pseudomonas aeruginosa using other techniques [12, 13]
Summary
Type IV pili (Tfp) are highly conserved macromolecular structures that fulfill diverse cellular functions, such as adhesion to host cells, the import of extracellular DNA, kin recognition, and cell motility (twitching). We show that MglA complexed to GTP recruits a newly characterized Tfp regulator, termed SgmX, to activate Tfp machines at the bacterial cell pole This mechanism ensures spatial regulation of Tfp, explaining how MglA switching provokes directional reversals. This discovery paves the way to elucidate how polar Tfp machines are regulated to coordinate multicellular movements, a conserved feature in twitching bacteria. Depending on associated cytoplasmic motors (PilB and PilT), the rotation of PilC would promote assembly (PilB-dependent) or deassembly (PilT-dependent) of the major pilin PilA subunits into filaments recruited at the periplasmic side of the Tfpa complex. M. xanthus motility plays a crucial role to swarm, predate on prey bacteria, and build differentiated multicellular structures
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
