Predator MX: Jack the Rippler
No, not a new hunter-killer drone, neither is it the n+1 installment in the sci-fi horror series. Rather, Myxococcus xanthus. Again.
Source: US Air Force
M. xanthus is a highly cooperative bacterium, as we have already seen: when starved, most cells “commit suicide” while a few form spores, to survive the lean times. But M. xanthus also cooperates when times are good and food plentiful: M. xanthus cells form swarms, which envelope their prey and increase the concentration of digestive enzymes they secrete to the environment.
M. xanthus also ripple together to better ingest the nutrients released after digesting their prey. To do so, they use a type of pilus (motility organ, like a bacterial tentacle) called type IV secretion pili. But amazingly enough, in mutant M. xanthus that are unable to make these pili, a new mechanism for cooperative swarming evolved. In 2003, Velicer & Yu from the University of Tuebingen have used a group of mutant M. xanthus, which are lacking the type IV pili gene to show that cooperative swarming can evolve using an alternative mechanism. The mutant bacteria do that by forming a physical net of sugars and proteins connecting them — and their rippling motion — together. Watching behavior evolve: how cool is that?
Finally, a movie of M. xanthus swarming & rippling:
Velicer, G., & Yu, Y. (2003). Evolution of novel cooperative swarming in the bacterium Myxococcus xanthus Nature, 425 (6953), 75-78 DOI: 10.1038/nature01908
Berleman, J., Chumley, T., Cheung, P., & Kirby, J. (2006). Rippling Is a Predatory Behavior in Myxococcus xanthus Journal of Bacteriology, 188 (16), 5888-5895 DOI: 10.1128/JB.00559-06
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