Myxobacteria cells have two types of motility: S-motility driven by pili and A-motility whose mechanism is not clear yet. Biologist found the existence of nozzle-like structures in both cell ends. [1]

These nozzle-like structures are filled with slime, which contains polyelctrolyte gels [1]. The swelling property of polyelctrolyte gels leads to slime secretion from nozzle-like structures and generates a propulsive force. Taking all the effective nozzle-like structures into account, the propulsive force is calculated to be around 50~150 pN [1]. The authors hypothesize that slime secretion may be the mechanism of A-motility [1].

There might be other processes that provide the driven force for A-motility.  More experimental evidence is still needed to verify this hypothesis. However, in reference [2], the author considers a special case, flailing motion of myxobacteia observed in [3], and based on an elastic-but-inextensible-filament model, he finds out that the force generated by A-engine is consistent with the prediction made in [1], thus strengthening their hypothesis about the mechanism of A-motility. The model can provide a novel prospective for studying the bending and alignment when myxobacteria collide.

References:

[1] Wolgemuth, C., E. Hoiczyk, D. Kaiser, and G. Oster. 2002. How myxobacteria glide. Curr. Biol. 12:369–377.

[2] Charles W. Wolgemuth. Force and Flexibility of Flailing Myxobacteria. Biophysical Journal Volume 89 August 2005 945–950.

[3] Alfred Spormann and Dale Kaiser. Gliding Movements in Myxococcus xanthus, 1995.