Recombination is also a source of variability. The sources may be chromosomes from two different bacteria. Specialized if due to improper detachment of prophage from bacterial chromosome. Plasmid DNA transfer may not result in recombination, but only in the acquisition of the plasmid by the recipient. Transposons are genes that can move to other sites on a DNA molecule or from one DNA molecule to another.
More complex transposons have other genes between two insertion sequences.
These complex transposons often carry genes that make the bacteria resistant to antibiotics. The movement of a transposon is catalyzed by the tranposase enzyme. Transposase recognizes the inverted repeats belonging to insertion sequences. The inverted repeats in the insertion sequences and the target sequences are not homologous sequences. Transposons can move between chromosomes, between plasmids, and between plasmid and chromosome.