Open Access

Albrecht Kleinschmidt, Dimitrij Lang, C. Plescher, W. Hellmann, J. Haass, Rudolf K. Zahn, A. Hagedorn

• 1. Electron micrographs of ultra-thin sections of Staphylococcus aureus and Micrococcus lysodeikticus in Vestopal as embedding medium disclose a multiplicity of DNA containing threads with varying interparticular distances. 2. The diameter of these threads is about one tenth of the average optimal section thickness. 3. This section thickness inevitably is implicated in the visualization of the internal distances between the threads as well as in some common trends in the DNA pool, a fact that has to be accounted for in the analysis of the macromolecules. 4. By spreading lysozyme protoplasts of M. lysodeikticus on a water-air interface in a Langmuir trough and by transferring this surface layer to carbon supported Formvar films, two-dimensional systems can be demonstrated which as a thread of constant width comprise the total DNA content of one microorganism each. 5. Such a macromolecular system shows equally shaped, coiled loops in a peripheral zone and many crossings towards the center. Branching of threads never has been observed so far. From this evidence we conlude: a) Intracellular DNA in these bacteria seems to exist in one pool as a “woolen ball” which is centered in the cytoplasm as a more or less dense object. b) This “woolen ball“ embodies the total amount of DNA most probably as one single threadlike unit. 6. Partial destruction of the thread system of protoplasts will result upon changing optimal spreading conditions. 7. The same kind of destruction is shown upon isolation of the DNA from protoplasts, the length of the threads being an inverse function of the number of precipitation steps showing purification.