"The bacteria have evolved to exploit this structural failure as a strategy," says lead author Roman Stocker, an associate professor in MIT's Department of Civil and Environmental Engineering, whose research focuses on the ecology and biophysics of ocean microbes. "E. coli and other multiflagellated microbes have to synthesize and maintain all those flagella. But marine bacteria are able to achieve the same functionality with just one flagellum by turning physics on its head. It's controlled failure."
Stocker's co-authors on the paper are graduate student Kwangmin Son and postdoc Jeffrey Guasto. Their research was funded by the National Science Foundation.
Understanding how marine microbes use controlled failure to change swimming direction is useful in its own right: Despite their small size, marine microorganisms are at the base of the ocean food chain, and can cause red tides, decimate coral reefs or clean up oil spills. But this work also may have future applications in soft robotics or bioengineered systems for drug delivery.
"A single actuator, the flagellum, enables both propulsion and turning in these bacteria," Guasto says. "This is a well-known principle in robotics called 'underactuation,' but it is rarely considered at the micrometer scale."
Stocker attributes the insight that buckling is the mechanism responsible for the flick to the "engineering bias" stemming from the team's knowledge of mechanics: "When our high-speed imaging showed that flicks only occurred during forward motion, we intuited that this implied compression, and thus the potential for buckling." But the key to discovering the mechanism was in the high spatial and temporal resolution of the imaging technology, he says.
Bacterial three-point turn
The researchers studied the swimming patterns of the bacterium Vibrio alginolyti
|Contact: Denise Brehm|
Massachusetts Institute of Technology