[Specificity of introducing the transposon that determines chloramphenicol resistance (Tn9) into the chromosome of Escherichia coli K-12].

Translocation of Tn9 coding for chloramphenicol-resistance from lambdaatt80 genome into bacterial chromosome was studied. Three preferential sites of Tn9 integration, attTn9A, ATTTn9B and attTn9C, were found on the chromosome of Escherichia coli K-12; attTn9A was mapped between purD and rpoB loci, attTn9B was cotransducible with argG, attTn9C was located between 61 and 66 minutes of the standard E. coli K-12 genetic map. The integration of Tn9 in these att sites occurs with almost equal probability. Tn9 integrated in attTn9A shown significantly higher frequency of excision and P1-transduction frequency than Tn9 integrated in either of two other attTn9 sites.