期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1976
卷号：73
期号：2
页码：563-567
DOI：10.1073/pnas.73.2.563
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Electron microscopy of disrupted Escherichia coli cells under certain conditions revealed loops of a fiber 120 A in diameter which were attached to the cell envelope and showed a 130 A repeating beaded substructure. These fibers were detected only when the cells were lysed in 0.15 M NaCl solutions directly on the electron microscope supporting films and if the dehydration steps began within 2 min of lysis. Under these conditions examination of cells lysogenic for phage lambda after superinfection with lambda wild type or deletion mutants disclosed short loops of a 120 A diameter fiber free of the cell envelope. Because the contour length of these loops was proportionate to the DNA content of the superinfecting lambda phage, it was concluded that the fibers contained DNA condensed 6.5-fold in blocks of about 250 base pairs.
