Genetic analysis of mutations in the transfer genes of pDU202 tra::Tn10 plasmids, caused by the excision of Tn10

Abstract

Transfer-deficient derivatives of pDU202 (a Tc^s deletion mutant of R100-1) caused by the insertion of Tn10 into the R factor's transfer genes have been described previously. Tetracyline-sensitive mutants of four of these were selected. In the majority of cases the Tc^s mutation was caused by a deletion of the Tc^r genes which was often accompanied either by a deletion of some of the flanking transfer genes or by a secondary mutation which was probably an inversion. A number of preferred end points for the deletions and inversions occur in the transfer operon of pDU202. Analysis of the mutants by complementation tests with Flac tra elements confirmed that the order of genes in the promoter distal part of the tra region of pDU202 is traKBCFHGSD and traI.