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Abstract

Different membrane fractions of Staphylococcus aureus obtained during the preparation of the enzyme II specific for lactose of the PEP-dependent phosphotransferase system were examined by means of the electron microscope. The cytoplasmic membrane has been disrupted by the isolation procedure into very small fragments which mostly form closed vesicles with a diameter of only 300–600 Å. Treatment with Triton X-100 immediately causes a considerable swelling of the vesicles to a diameter of 600–1000 Å, and, moreover, changes the membrane structure itself: The membrane widens to a thickness of 125–140 Å and becomes extremely asymmetric. After removal of lipids and Triton the delipidated membranes, no longer forming closed vesicles, consist of flat or slightly curved sheets of 300–600 Å in diameter with a distinct trilamellar appearance, 70–75 Å thick.