Surface arrays on the wall of Sporosarcina ureae

Thin sections of the cell wall of Sporosarcina ureae revealed two structurally distinct layers: a continuous amorphous zone, approximately 15 nm thick, which was adjacent to the plasma membrane, and an overlying periodic zone, approximately 16 nm thick. Sequential Triton X-100 and lysozyme treatment of isolated walls produced small fragments of the outer regular structure which allowed high-resolution, negatively stained images suitable for optical diffractometric analysis. These data suggested a tetragonal array of complex polygonal units of C-C spacing = 12 nm, with each unit joined to another by two delicate linkers. The array was entirely proteinaceous, consisting of a 150,000-dalton polypeptide which had a high affinity for Mg2+. It proved to be sensitive to chelating agents, 5 mM concentrations of Ca2+, Sr2+, or Ba2+, proteases, heat greater than or equal to 45 degrees C, sodium dodecyl sulfate, and pH greater than or equal to 5.8, but magnesium offered protection against the chelating agents and the deleterious salts.