Oozing, Cruising Bacteria

Many organisms, including ourselves, enjoy the benefits of motility. Even bacteria have to be motile to explore their surroundings, look for nutrients, and figure out when they should grow and divide. But often bacteria don’t have any external limbs or appendages they can use to propel them forward, so they have to use a different strategy.

Recently, Joel Tchoufag and colleagues in Kranthi Mandadapu’s group in the Department of Chemical and Biomolecular Engineering have found that some bacteria are able to move over a surface using slime. Through a collaborative study recently published in Proceedings of the National Academy of Science, they found that Myxcoccus xanthus, a species of bacteria, can secrete a viscous polysaccharide slime that lubricates the surface, allowing them to glide. Oscillations and ridges on the bacteria body interact with the slime to thrust the bacteria forward. It’s almost as if they’re surfing on the slime waves.

As the surface below softens, the gliding speed decreases. To generate enough force, surface tension at all interfaces contributes to local pressure build-up at the front of the bacterial cell, changing the shape of the soft surface and eventually thrusting the bacterium forward.

Tchoufag and Mandadapu started their work on individual bacterial cells, but there’s more to explore. For example, it is still unclear exactly how the size and shape of the bacterial cell change these interactions. Additionally, myxobacteria often live in large groups of cells that communicate with surrounding cells. Tchoufag and Mandadapu are eager to add more variables to the current gliding model to account for the variances seen in these bacteria.

Just like slugs and snails, many bacteria rely on self-secreted slime to glide along surfaces. Image Design: Alexandra Ramsey. Snail: Wikimedia Commons/Troughnof. Bacteria: Rocky Mountain Laboratories, NIAID, NIH. Slug: Wikimedia Commons/Carla Isabel Ribeiro.

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