||"Myxococcus xanthus, a bacterium that forms fruiting bodies, moves by gliding motility utilizing dual motility systems that differ both genetically and morphologically [system
A, having at least 21 genetic loci and moving mainly single
cells, and system S, having at least 10 genetic loci and moving
groups (rafts) of cells] [Hodgkin, J. & Kaiser, D. (1979) Mol. Gen. Genet. 172, 177-191]." "[Investigators] also used time-lapse video microscopy to more directly study gliding motility of M. xanthus. Consistent with the swarming data and morphology of the edges of colonies presented above, [investigators] found that A+S- cells moved at a rate of 2-4 µm/min on 1.5% agar but barely moved on 0.3% agar (the moving speed was <0.5 µm/min and many cells appeared to vibrate in place) (Table 3). On the other hand, A-S+ cells did not exhibit much movement when initially plated onto 1.5% agar: however, motility became better after 1.0 or 1.5h. When S-motile cells were plated on 0.3% agar, they were motile immediately. In addition, the speed of cell movement was 3-5 times faster on 0.3% agar than on 1.5% agar, based on analysis of the video images (Table 3). Such movement could often be observed in real time and the maximum rate of movement [investigators] observed was >20 µm/min at 22°C."