Rapid methods for the study of both stable and unstable plasmids in Pseudomonas

Rapid methods for the analysis of degradative plasmids in Pseudomonas are described. Bacterial lysates prepared with alkaline sodium dodecyl sulphate were vigorously stirred in the presence of antifoam agent. Samples were subjected to agarose gel electrophoresis to detect plasmid DNA. After a short period of centrifugation on a sucrose gradient, the lysates yielded plasmid DNA of sufficient purity for restriction endonuclease digestion without further treatment. The methods have proved most useful in the extraction of previously undetected plasmid DNA, some of which appears to be unstable.