Paracrystalline Cell Wall Surface Layers of Different Bacillus stearothermophilus Strains

Abstract

We compared the protein and glycoprotein patterns of 39 Bacillus stearothermophilus strains of various origins by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The ultrastructures of the cell walls of intact cells were examined by freeze-etching, negative-staining, and thin-sectioning techniques. A total of 30 strains possessed a paracrystalline protein or glycoprotein surface layer (S-layer) which resembled the highest-molecular-weight band(s) on the electrophoretograms. We found a remarkable heterogeneity in the molecular weights of the S-layer subunits and the geometry and constants of the S-layer lattices, even among closely related strains. All of the strains examined were equally susceptible to lysozyme, indicating that the S-layers have pores at least 3.5 nm wide.