Ultrastructural Details of the Apparatus of Gliding Motility of Myxococcus fulvus (Myxobacterales)

Abstract

Cell was preparations of the myxobacterium Myxococcus fulvus were fractionated by ion-exchange chromatography. Highly ordered chain-like structures were found in certain fractions when negatively stained specimens were inspected in the transmission electron microscope. The chain-like structures, which we call ‘strands’, were built up of two structural components: (1) a ring with an outer diameter of 12 to 15 nm which was regularly stacked with a periodicity of 14 nm. and (2) an elongated component, measuring 11·0 × 2·8 nm. Each ring appeared to be linked to the next one by two elongated components. Their orientation towards the elongated components was somewhat variable, which suggests a certain flexibility and a potential for conformational changes of the ‘strands’. Three or more of the ‘strands’ appeared to form a superstructure, which is defined as ‘ribbon’, which might undergo conformational changes leading to the observed strinkage in the transverse direction of about 40%. We suggest that the structures described crease contraction waves in the surface of the myxobacterial cell, and that those waves drag the cell along. The organization of the apparatus of gliding motility in the cell surface could only very rarely be seen. An exceptionally well-preserved whole cell in a negatively stained specimen showed a surface pattern consisting of parallel ridges, indicated by dark stain lines and 40 to 50 nm wade running helically around the cell pole. At a higher magnification these parallel ridges showed a distinct, periodic substructure normal to their long axis and with a spacing of 14 nm. which corresponds exactly to the periodicity of the stacked rings within the ‘strand’.