In broth cultures thp stabje L-forms of E. coli B and TV 1655 F+ grow as spherical elements with diameters of 0.05 , u up to more than 2 p. Particles below 0.3 p in diameter are probably not, able t o propagate. L-form cells, growing in agar media, are highly pleomorph.Ultrathin sections through L-form cells show that there are no ce!l wall structures. The cells are always surrounded only by the cytoplasmic membrane. Therefore, the L-forms of the two E. coli strains under study may be designa+ed as stable L-forms of the protophst type-UnIike normal rods t h e nucleoids of L-form cells are not marked off clearly from the cytoplasm. There are often vacuoles in the elements, which are surrounded by a typically triple layered membrane. The cytoplasmic membrane may produce local outgrowths of different size. Frequently, intracellular membranes are present in L-form cells. They may be seen as triple layered unit membranes or as st.ructures with 5 and more lagers. With il centre to centre distance of the dark layers of 41 A they are similar t o myelin structures.The quintuple layered structures, which can be found also extracellular, are probably produced by a close contact between the cytoplasmic membrane and the membrane of vacuoles. Formation and function of the intracellular membranes are discussed.Wabxend der Iet,zten Jahre konnten wir mittels Penicillin stabile L-Formen einiger E. coli-Starnme gewinnen (TAUBENECK u. SCHUHMANN 1966, SCHUHMANN u. TAUBENECK 1969. Die L-Form-Stamme wachsen als pleomorphe Zellen in Agarnahrboden oder als kugelige Elemente unterschiedlicher Grofie in fliissigen Medien. Im folgenden wird anhand von zwei Stammen iiber die Ultrastruktur dieser stabilen L-Formen berichtet.
Material und MethodenOrganismen: Zunachst wurden die stabilen L-Formen von E. coli B und W 1655 F+ fur die elektronenmikroskopischen Unt,ersuchungen ausgewahlt. Uber Induktion und Ziichtung der stabilen L-Fornien wurde bereits ausfuhrlich berichtet (TAUBENECK u. SCHUHMANN 1966, SCKUHMANN u. TAUBENECR 1969).') Herrn Prof. Dr. H. WARTENBERG zum 70. Gebiirtstag gewidmet.
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