Mini-Mu transduction: cis-inhibition of the insertion of Mud transposons.

Mud (mini-Mu) transposons are defective phage Mu genomes that conserve the Mu ends. The transduction of Mud transposons is strictly dependent on Mu complementation, inefficient, and affected by modifications in the Mud internal sequences. The transduction of Mud transposons depends on transposition, which appears to be low, relative to wild-type Mu. Insertions of Mud into a plasmid can be frequently recovered among transductants; new Mud insertions into plasmids that already have both Mu ends, or just one, are rarely found. This suggests that the presence of Mu ends "immunizes" the plasmid against further insertion. This phenomenon may be similar to the transposition immunity of Tn3.