Force generation by groups of migrating bacteria. Author Benedikt Sabass, Matthias Koch, Guannan Liu, Howard Stone, Joshua Shaevitz Publication Year 2017 Type Journal Article Abstract From colony formation in bacteria to wound healing and embryonic development in multicellular organisms, groups of living cells must often move collectively. Although considerable study has probed the biophysical mechanisms of how eukaryotic cells generate forces during migration, little such study has been devoted to bacteria, in particular with regard to the question of how bacteria generate and coordinate forces during collective motion. This question is addressed here using traction force microscopy. We study two distinct motility mechanisms of Myxococcus xanthus, namely, twitching and gliding. For twitching, powered by type-IV pilus retraction, we find that individual cells exert local traction in small hotspots with forces on the order of 50 pN. Twitching bacterial groups also produce traction hotspots, but with forces around 100 pN that fluctuate rapidly on timescales of <1.5 min. Gliding, the second motility mechanism, is driven by lateral transport of substrate adhesions. When cells are isolated, gliding produces low average traction on the order of 1 Pa. However, traction is amplified approximately fivefold in groups. Advancing protrusions of gliding cells push, on average, in the direction of motion. Together, these results show that the forces generated during twitching and gliding have complementary characters, and both forces have higher values when cells are in groups. Journal Proc Natl Acad Sci U S A Volume 114 Issue 28 Pages 7266-7271 Date Published 07/2017 ISSN Number 1091-6490 DOI 10.1073/pnas.1621469114 Alternate Journal Proc. Natl. Acad. Sci. U.S.A. PMCID PMC5514709 PMID 28655845 PubMedPubMed CentralGoogle ScholarBibTeXEndNote X3 XML