Bacteria reproduce by the process of binary fission. In this process, the chromosome in the mother cell is replicated and a copy is allocated to each of the daughter cells. As a result, the two daughter cells are genetically identical. If the daughter cells are always identical to the mother, how are different strains of the same bacterial species created? The answer lies in certain events that change the bacterial chromosome and then these changes are passed on to future generations by binary fission. In this chapter, you will explore some of the events that result in heritable changes in the genome: genetic transfer and recombination, plasmids and transposons.