Mechanisms of transposition in bacteria.

The transposable elements of bacteria are diverse in size, functional arrangement, DNA sequence, and in their modes of transposition. We review here data suggesting that the kanamycin-resistance transposon Tn5 moves without replicating (conservative transposition), but the ampicillin-resistance transposon Tn3 is duplicated when it transposes, and that both the chloramphenicol-resistance transposon Tn9 and bacteriophage Mu are replicated in some events but not in others. A model is presented in which conservative and replicative transposition are alternative branches of a single pathway.