title: Spontaneous deletions in the TOL plasmid pWW20 which give rise to the B3 regulatory mutants of Pseudomonas putida MT20.
abstract: The size of the TOL plasmid pWW20 from Pseudomonas putida MT20, as measured by analysis of agarose electrophoresis gels after restriction endonuclease hydrolysis, was 270-280 kilobase pairs (kb). During growth on benzoate, MT20 segregates strains carrying mutations in the plasmid regulatory gene xylS; these so-called B3 strains retain the ability to grow on m-xylene (Mxy+) but do not grow on its metabolite m-toluate (Mtol-) and have also lost the ability to transfer the plasmid (Tra-). Analysis of restriction digests of plasmid DNA from seven such segregants, independently isolated, showed that pWW20 had undergone extensive deletions of 90-100 kb. All the deleted plasmids had lost a common core of DNA, of about 72-80 kb, but in class A mutants the deletion extended at one end of this core and in class B mutants at the other end. Class A and B mutants also differed in their rate of growth on m-xylene as a result of differences in the level of expression of their plasmid-coded catabolic enzymes. This suggests that an additional gene, involved in regulating levels of gene expression, is located in the region uniquely deleted in the class B mutants.
mesh_terms: D002872:Chromosome Deletion; D004262:DNA Restriction Enzymes; D004269:DNA, Bacterial / Q000235:genetics; D004587:Electrophoresis, Agar Gel; D005798:Genes, Bacterial; D005809:Genes, Regulator; D009154:Mutation; D010957:Plasmids; D011549:Pseudomonas / Q000201:enzymology / Q000235:genetics* / Q000254:growth & development
chemical_list: D004269:DNA, Bacterial; D004262:DNA Restriction Enzymes