NEW DERIVATIVES OF TOL PLASMID PWW0

Two new segregants, PPW1-1 and PPW161-1, of Pseudomonas putida were is olated from the stock cultures PaW85(pWW0) and PaW85(pWW0-161). Strain PPW1-1 had lost its ability to grow on m-xylene but was able to grow on m-toluate. A deletion of the left-hand of transposon Tn4651, includ ing the upper-operon genes, had taken place in plasmid pWW0mut1, isola ted from strain PPW1-1. Additional deletions were observed in pWW0mut1 after 'benzoate-curing' (plasmids pWW0mut15, pWW0mut19, pWW0mut27). T he genes of the upper-operon and beginning of the meta-operon were del eted from pWW0-161mut1, isolated from strain PPW161-1. Despite this de letion, cells of PPW161-1 grew on all normal TOL plasmid substrates. T he Tol- phenotype was stable in cells of PPW161-1 growing on benzoate. We propose that this is because in cells of strain PPW161-1 the catab olic genes deleted from pWW0-161mut1 were integrated into the chromoso me at the site where the (chromosomally encoded) ortho-pathway genes a re located, resulting in the inability of the cells to use this pathwa y.