Structure of the regular surface layer of Sporosarcina ureae

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Abstract
Optical diffraction and computer image processing of electron micrographs were employed to analyze the structure of the regular surface layer of S. ureae at high resolution. Negatively stained preparations of regular surface layer fragments showed 2 types of tetragongal pattern, each having p4 symmetry in projection with a = 12.8 nm. Although the 2 patterns differed greatly in overall appearance, both had a common pattern of areas of high stain density which was interpreted as arising from gaps or holes in the structure. These holes may be related to a protective role of the regular surface layer, whereby hostile environmental agents (such as muramidases) larger than about 2 nm would be screened from the underlying layers of the bacterial surface, while the free passage of nutrients and waste products into and out of the cell would still be allowed.