Transposable phages, DNA reorganization and transfer

- Transposable phages are widespread in the bacterial world.
- Related to their mode of packaging, transposable phages preform generalized transduction.
- The replicative transposition mode of replication of the transposable phages inevitably leads to profound reorganisation of their host genome.
- Rearrangements include translocations of random chromosomal segments onto co-residing conjugative plasmids or genomic islands. These ensure the spreading of the translocated DNA.

Transposable bacteriophages have long been known to necessarily and randomly integrate their DNA in their host genome, where they amplify by successive rounds of replicative transposition, profoundly reorganizing that genome. As a result of such transposition, a conjugative element (plasmid or genomic island), can either become integrated in the chromosome or receive chromosome segments, which can then be transferred to new hosts by conjugation. In recent years, more and more transposable phages have been isolated or detected by sequence similarity searches in a wide range of bacteria, supporting the idea that this mode of HGT may be pervasive in natural bacterial populations.