Bacteria have been swimming before anything else in the world was walking, but we know relatively little about their method of locomotion. New research shows how bacteria use their flagella to run and tumble their way through a gooey medium. What you see in the above video at first looks like disorganised, random behaviour. But according to a new paper by scientists from the University of Cambridge in the Annual Review of Fluid Mechanics, these E. coli know what they're doing.
E. coli look a bit like mutant sperm. They have a single big head, but they have three different tails. These tails propel them through a medium by moving in a kind of rotating helical motion. When the bacteria have somewhere to go, these tails bundle together and move counter-clockwise. When the bacteria have to make a turn, one tail separates itself out and moves clockwise. This makes the bacteria tumble from its normal path and spin off in a new direction. Once it's oriented the right way, E. coli bundles up its tails and spins them all counter-clockwise again.
This run-tumble-run movement lets us know how other bacteria move through liquid. Here's a slow-motion look at the bacteria in action:
This is of interest because, as the scientists ask in their paper, "How exactly can a title bundle of multiple flagella open and close without jamming under the uncoordinated action of a few motors?" In other words, why aren't these things a hopeless tangle? If we can answer that, we might be able to create fluids, that are impervious to E. coli and other similar bacteria. Or we might be able to find a way to prevent all the uncoordinated cords and motors in our lives from tangling.