COMPARATIVE-STUDIES OF S-LAYER PROTEINS FROM BACILLUS-STEAROTHERMOPHILUS STRAINS EXPRESSED DURING GROWTH IN CONTINUOUS-CULTURE UNDER OXYGEN-LIMITED AND NON-OXYGEN-LIMITED CONDITIONS

The specific properties of S-layer proteins from three different Bacil lus stearothermophilus strains revealing: oblique, square, or hexagona l lattice symmetry were preserved during growth in continuous culture on complex medium only under oxygen-limited conditions in which glucos e was used as the sole carbon source. When oxygen limitation was relie ved, amino acids became metabolized, cell density increased, and diffe rent S-layer proteins from wild-type strains became rapidly replaced b y a new common type of S-layer protein with an apparent subunit molecu lar weight of 97,000 which assembled into an identical oblique (p2) la ttice type. During switching from wild-type strains to variants, patch es of the S-layer lattices characteristic for wild-type strains, granu lar regions, and areas with oblique lattice symmetry could be observed on the surface of individual cells from all organisms. The granular r egions apparently consisted of mixtures of the S-layer proteins from t he wild-type strains and the newly synthesized p2 S-layer proteins fro m the variants. S-layer proteins from wild-type strains possessed iden tical N-terminal regions but led to quite different cleavage products upon peptide mapping, indicating that they are encoded by different ge nes. Chemical analysis including N-terminal sequencing and peptide map ping showed that the oblique S-layer lattices synthesized under increa sed oxygen supply were composed of identical protein species.