Researchers are using genetically engineered E. coli to power micromotors, with the swimming bacteria causing the motors to rotate in a similar fashion to a river rotating a watermill.
This from Phys.org:
[An] important requirement for any bacteria-powered micromotor is the ability to control the micromotor’s motion. To do this, the researchers genetically modified the E. coli strain to express a light-driven proton pump called proteorhodopsin that uses photon energy to pump protons against the electrochemical gradient, which increases the bacteria’s swimming speeds. By illuminating the bacteria-powered micromotors with different light intensities, the researchers could then control the speed of the micromotors.
Researchers believe this development could find practical applications in medicine, such as drug and cargo delivery.