[Chromosomal structures of Pseudomonas testosteroni. I. Isolation and characterization of the chromosomal complexes....

After lysis of Pseydomonas testosteroni with lysozyme and non-ionic detergents different DNA-protein complexes can be separated in 5-25% (w/v) neutral sucrose gradient. The protein to DNA ratio of these complexes varies between 0.5-4.5 to 1, whereby the faster sedimenting forms contain more protein than the slower sedimenting ones. Different initial rates of DNase digestion may indicate various degrees of DNA packing in these complexes. The chromosomal complexes of Pseudomonas testosteroni are relatively stable towards pronase. Treatment with RNase or sodium dodecylsulphate is accompanied by a dramatic increase in viscosity and decrease in relative density. It suggests that DNA in these complexes is maintained in its supercoiled form by RNA molecule(s) in a similar way as in isolated chromosome of E. coli.