Electron Microscopic Studies on the Folded Chromosome of Escherichia coli
This extract was created in the absence of an abstract.
Excerpt
The chromosome of Escherichia coli can be isolated in a highly folded conformation by gentle lysis at room temperature with nonionic detergents in 1.0 m sodium chloride (Stonington and Pettijohn, 1971). The folded chromosomes contain all of the nascent RNA chains of the cell and core RNA polymerase, but no ribosomes, and they sediment as 1300- to 2200-S particles depending on the extent of their replication. The compactness of the folded chromosome may be accounted for because: (a) the DNA is folded into loops, somewhere between 12 and 80 loops per chromosome, and (b) each loop is supercoiled (Worcel and Burgi, 1972).
Lysis at 0 to 4°C results in DNA particles containing membrane fragments and having a much higher sedimentation coefficient, 3000 to 4000 S (Pettijohn et al., 1973; Worcel et al., this volume).
In order to gain an insight into the manner and nature of the DNA folding, we...
