Ultrastructural organization of the cell wall surface layer in Sulfobacillus thermosulfidooxidans

It was shown by the techniques of freeze-fracturing, negative staining, and thin sectioning that protein subunits of the S-layer of Sulfobacillus ther mosulfidooxidans VKM B-1269 (= DSM 9293) are dimers arranged in parallel st rands oriented at an angle of 15 degrees to each other with a spacing const ant of 140 Angstrom (oblique p2 symmetry). A fast and simple procedure, whi ch involved the treatment of whole cells with 5 M lithium chloride, was use d for the isolation of the S-layer. After removal of LiCl by dialysis, the isolated S-layer protein was capable of self-assembly into regular structur es that exhibited the same oblique p2 symmetry.