Ultrastructural organization of membrane system in Sulfobacillus thermosulfidooxidans

It was shown by the techniques of freeze-fracturing and thin sectioning tha t the membrane system in Sulfobacillus themosulfidooxidans, as in other gra m-positive bacteria, includes, in addition to the cytoplasmic membrane (CPM ), intracytoplasmic membranous structures. CPM in S. thermosulfidooxidans c ells was established to contain large zones having a lamellar structure, wh ich included layers of inverted membranes. The inverted membranes incorpora ted into the lipidic bilayer of CPM were characterized by the wrinkled stru cture of leaflets and the presence of a thickened central electron-dense la yer. Possible functions of intramembranous structures in the form of invert ed membranes are discussed. Another peculiarity of the membrane system in s ulfobacilli was the occurrence in CPM of numerous slitlike invaginations, n ot found earlier in bacteria, which resemble those in some yeast species.