Microscopic methods for distinguishing among three cell types in TOL plasmid-carrying Pseudomonas putida cultures

Microscopic methods were developed that enable the sensitive quantification of different cell types that are generated by plasmid instability processes when Pseudomonas putida PaW164 (X+), which carries a TOL plasmid (pWW0-164), is grown in chemostat culture. Cells that have lost the structural TOL genes (X-) or the entire TOL plasmid (X0) can be quantified in a background of 6000 X+ cells using catechol agarose miniplates. X0 cells can be quantified in a background of 3500 X+ or X- cells using carbenicillin agarose miniplates. These methods represent significant improvements in sensitivity over conventional plating methods.