Reduced transposition in rho mutants of Escherichia coli K-12

Substantially reduced frequencies of transposition for the transposons Tn5 and Tn9 and the insertion sequences IS1 and IS5 were observed in several rho mutants of Escherichia coli K-12 compared with those observed in their isogenic wild-type counterparts. The lower transposition frequencies could be due to decreased supercoiling of DNA, to altered expression of required genes, or to aberrant transcription of transposon or target DNA resulting from the lack of transcription termination at Rho-sensitive sites in rho mutants.