title: Some properties of the chloramphenicol resistance transposon Tn9.
abstract: We have isolated variants of the plasmid RTF which have received the transposon Tn9 from bacteriophage P1Cm. We have shown by the formation of heteroduplex molecules between one RTF:Tn9 derivative and R100.1 that Tn9 is homologous to the r-determinant region of R100.1 which carries the determinants for chloramphenicol resistance. This suggests that Tn9 was derived from an r-det like structure by deletion, possibly mediated by one of the flanking IS1 elements. In spite of the similarity in structure between Tn9 and r-det however, we have demonstrated two distinct differences in the behavior of these two elements: 1) Tn9 but not r-det, is able to amplify, by a recA dependent mechanism, when cells harboring RTF::Tn9 are grown in the presence of chloramphenicol, and 2) Tn9, unlike r-det, does not form extrachromosomal circular molecules when RTF::Tn9 is tegrated into the bacterial chromosome.
mesh_terms: D002701:Chloramphenicol; D002874:Chromosome Mapping; D004251:DNA Transposable Elements; D004926:Escherichia coli / Q000235:genetics*; D005784:Gene Amplification; D010957:Plasmids; D011815:R Factors; D011995:Recombination, Genetic
chemical_list: D004251:DNA Transposable Elements; D002701:Chloramphenicol