Abstract
The isolated, formaldehyde-fixed nucleoid of E. coli has been analyzed by isopycnic centrifugation in CsCl density gradients. The membrane-free nucleoid bands at a density of 1.69 +/- 0.02 g/cm3. The membrane-associated nucleoid bands at a density of 1.46 +/- 0.02 g/cm3. Both species sediment to equilibrium as nearly monodisperse bands in CsCl, suggesting that the nucleoid components of DNA, RNA and protein are present in relatively constant ratios. These ratios are constant regardless of the position of the nucleoids in the heterogeneous sedimentation profile of a preparative sucrose gradient. The fixed nucleoids remain condensed during isopycnic centrifugation and there is no detectable loss of RNA from the nucleoid.
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- Hecht R. M., Taggart R. T., Pettijohn D. E. Size and DNA content of purfied E. coli nucleoids observed by fluorencence microscopy. Nature. 1975 Jan 3;253(5486):60–62. doi: 10.1038/253060a0. [DOI] [PubMed] [Google Scholar]
- Pettijohn D. E., Clarkson K., Kossman C. R., Stonington O. G. Synthesis of ribosomal RNA on a protein-DNA complex isolated from bacteria: a comparison of ribosomal RNA synthesis in vitro and in vivo. J Mol Biol. 1970 Sep 14;52(2):281–300. doi: 10.1016/0022-2836(70)90031-8. [DOI] [PubMed] [Google Scholar]
- Pettijohn D. E., Hecht R. RNA molecules bound to the folded bacterial genome stabilize DNA folds and segregate domains of supercoiling. Cold Spring Harb Symp Quant Biol. 1974;38:31–41. doi: 10.1101/sqb.1974.038.01.006. [DOI] [PubMed] [Google Scholar]
- Pettijohn D. E., Stonington O. G., Kossman C. R. Chain termination of ribosomal RNA synthesis in vitro. Nature. 1970 Oct 17;228(5268):235–239. doi: 10.1038/228235a0. [DOI] [PubMed] [Google Scholar]
- Stonington O. G., Pettijohn D. E. The folded genome of Escherichia coli isolated in a protein-DNA-RNA complex. Proc Natl Acad Sci U S A. 1971 Jan;68(1):6–9. doi: 10.1073/pnas.68.1.6. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Worcel A., Burgi E. On the structure of the folded chromosome of Escherichia coli. J Mol Biol. 1972 Nov 14;71(2):127–147. doi: 10.1016/0022-2836(72)90342-7. [DOI] [PubMed] [Google Scholar]
- Worcel A., Burgi E. Properties of a membrane-attached form of the folded chromosome of Escherichia coli. J Mol Biol. 1974 Jan 5;82(1):91–105. doi: 10.1016/0022-2836(74)90576-2. [DOI] [PubMed] [Google Scholar]