Horizontal gene transfer
The genome of "B. pseudomallei" consists of two replicons: chromosome 1 encodes housekeeping functions of the bacteria such as cell wall synthesis, mobility, and metabolism; chromosome 2 encodes functions that allow the bacteria to adapt to various environments. Horizontal gene transfer among bacteria has resulted in highly variable genomes in "B. pseudomallei". Australia has been suggested as the early reservoir for "B. pseudomallei" because of the high genetic variability of the bacteria found in this region. Bacteria isolated from Africa and Central and South America seem to have a common ancestor that lived in the 17th to 19th centuries. "B. mallei" is a clone of "B. pseudomallei" that has lost substantial portions of its genome as it adapted to live exclusively in mammals.