Periodic structure in the flagella and cell walls of a bacterium

Abstract

Electron micrographs of a non-spore forming, gram-positive, motile bacterium show the peritrichous flagella to have an external contour of a counterclockwise double helix and the cell wall to have a rectangular periodic structure clearly visible on the inside surface. The flagella are about 150 A in a diameter and have a well-defined cross structure with a periodicity along the flagella axis of 155 A. The nearly constant angle (27 to 35 degrees) that the striae of this cross structure make with the normal to the flagellar axis requires the external contour of the flagella to be a double rather than a single counterclockwise helix. The periodic structure in the cell wall appears to be caused by a rectangular array of spheres or hemispheres having diameters of about 115 A. The outside of the cell wall shows only a faint suggestion of this periodicity.