RT Journal Article SR Electronic(1) A1 Pickup, Roger W. A1 Williams, Peter A.YR 1982 T1 Spontaneous Deletions in the TOL Plasmid pWW20 which Give Rise to the B3 Regulatory Mutants of Pseudomonas putida MT20 JF Microbiology, VO 128 IS 7 SP 1385 OP 1390 DO https://doi.org/10.1099/00221287-128-7-1385 PB Microbiology Society, SN 1465-2080, AB 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., UL https://www.microbiologyresearch.org/content/journal/micro/10.1099/00221287-128-7-1385