The Mysterious Propulsion of Synechococcus

Ah, nanotechnology – the great salvation of humankind that will cure cancer, solve the energy crisis and provide for our eco-friendly manufacturing future. That’s assuming that we can figure out how to build the nanomachines we need of course. Which is where this comes in:

“The swimming of the marine cyanobacterium Synechococcus has been a longstanding puzzle. Synechococcus is ubiquitous in the euphotic zone of the worlds oceans making it a major primary producer. Approximately one third of the open ocean isolates are motile. It moves through seawater at speeds of 5 to 25 m/s while rotating about its long axis at about 1 Hz. It accomplishes this despite the complete absence of any observable motile apparatus such as flagella. A clue to Synechococcus’s propulsion comes from a bacterium that does not swim, but glides on surfaces…”

 

On the Mysterious Propulsion of Synechococcus. (2012) PLoS ONE 7(5): e36081. doi:10.1371/journal.pone.0036081
We propose a model for the self-propulsion of the marine bacterium Synechococcus utilizing a continuous looped helical track analogous to that found in Myxobacteria. In our model cargo-carrying protein motors, driven by proton-motive force, move along a continuous looped helical track. The movement of the cargo creates surface distortions in the form of small amplitude traveling ridges along the S-layer above the helical track. The resulting fluid motion adjacent to the helical ribbon provides the propulsive thrust. A variation on the helical rotor model allows the motors to be anchored to the peptidoglycan layer, where they drive rotation of the track creating traveling helical waves along the S-layer. We derive expressions relating the swimming speed to the amplitude, wavelength, and velocity of the surface waves induced by the helical rotor, and show that they fall in reasonable ranges to explain the velocity and rotation rate of swimming Synechococcus.

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