Frozen motion of gliding bacteria outlines inherent features of the motility apparatus

High-resolution data of actively gliding wild-type bacteria of four differe nt species and of four different gliding mutants of Myxococcus xanthus were obtained from scanning electron micrographs. By shock freezing and freeze drying, motility-associated surface patterns could be fixed and consequentl y distinct intermediate states of motion could be observed for the first ti me. It is shown that these topographic patterns are immediately lost when g liding motility is stopped by blocking the respiratory chain with potassium cyanide or sodium azide. From the surface topography, the mode of action o f the gliding apparatus of all four bacterial species examined can be descr ibed as a twisted circularly closed 'band'. During gliding, groups of nodes of the supertwisted apparatus show evidence of travelling like waves along the trichomes. However, the spacing between the nodes is not constant but varies within a certain range. This indicates that they are flexibly modula ted as a consequence of the gliding state of the individual trichome.