“…The mechanism by which gliding bacteria move on solid surfaces has been under discussion for many years. Many hypotheses exist which are based on different principles such as: directional extrusion of slime (Jahn, 1924;Henrichsen, 1972;Ridgeway & Lewin, 1973); contractile tubular elements in the cytoplasm (Schmidt-Lorenz & Kuhlwein, 1968 ;Schmidt-Lorenz, 1969;Bisalputra et al, 1975;MacRae & McCurdy, 1975, 1976Burchard et al, 1977); contraction waves along the cell surface (Graf, 1965;Pate & Ordal, 1967;Doetsch & Hageage, 1968;Halfen & Castenholz, 1971;Henrichsen, 1972;Halfen, 1973 ; Humphrey rt a/., 1979); polar fimbriation (MacRae & McCurdy, 1976); and excretion of surface-active material (Dworkin et al, 1983;Keller et al, 1983). In addition, at least in myxobacteria, there exists evidence for a considerable genetic complexity of the gliding machinery involving about 40 genes (for a review see Kaiser et al, 1979).…”