The structure of the macromolecular units on the cell walls of Bacillus polymyxa.

Electron micrographs of negatively stained preparations of cell walls of Bacillus polymyxa have been investigated by optical diffraction and optical filtering techniques. Images of single layers of the cell wall, from which the ' noise' has been filtered optically, show hollow, squareshaped morphological units arranged on a square lattice of side 100 A. Single-layer images showing the same pattern have been filtered from moir6 patterns arising from two overlapping single layers. The morphological units are composed of four smaller subunits. The optical diffraction patterns from regions of two overlapping layers show extra reflexions which are attributed to multiple electron scattering.