Analysis of the intracellular DNA-protein associations in Escherichia coli and Bacillus subtilis.

Intracellular DNA-protein complexes free of RNA have been isolated from Escherichia coli B and Bacillus subtilis 168. The complexes were characterized by the protein/DNA ratio (approximately 0.4) and by physico-chemical parameters. Using electrophoretic methods, it was shown that the protein component of the studied complexes from both microorganisms contained acid and basic proteins. The composition of the protein component of complex isolated from Bacillus subtilis was studied with respect to the growth rate of the culture. It was found that the sample from a slowly growing culture contained always higher amounts of basic proteins with a lower electrophoretic mobility than that from a culture growing more rapidly. A possible role of these proteins is discussed.