Bacteria possess extrachromosomal loops of DNA called plasmids. Plasmids are small, self-replicating loops of DNA with about 10 to 50 genes. They are not essential for the survival of the bacterium. New segments of DNA acquired in transformation may attach to the plasmids of a bacterium, or entire plasmids may be recovered from the local environment. Additionally, plasmids can sometimes be lost in a process called curing, which can occur spontaneously or can be induced by certain environmental factors.
