Micron-sized bacteria represent the smallest and most abundant life form on Earth. Strikingly, bacteria are motile despite their small size and understanding their swimming mechanics is both intriguing and important. Although bacterial motility has been studied for half a century, we recently discovered a new mechanism of reorientation, used broadly among marine bacteria, which all (95% of swimming species) have only a single flagellum, in contrast for example to E. coli. By combining video microscopy at up to 2000 frames/s, image analysis, and mechanical stability theory, we visualized the dynamics of the cell and its flagellum as it changes swimming direction and discovered that the mechanism that allows them to reorient is a buckling instability of their flagellum. This project revealed an unexpected role of flexibility in the locomotion of prokaryotes, whose flagella are typically assumed to be rigid. Intriguingly, it shows how structural failure can be turned into biological function, a dramatic and elegant adaptation by the smallest organisms on the planet.

Now working on this theme: Kwangmin Son, Jeff Guasto.