For bacteria, addiction to DNA can be a life or death situation. Lose that DNA and the bacterium suffers an unfortunate toxic death.
Many bacteria easily transfer DNA amongst themselves in the forms of plasmid DNA. Plasmids are mobile genetic elements that replicate independently of the chromosome. These small circular pieces of DNA often contain genes that provide its carrier a survival advantage under specific environmental conditions. For example, if a bacterium contains a plasmid with an antibiotic resistance gene, it can survive antibiotic treatment. But, the plasmid is not beneficial to its host cell in all situations and poses a metabolic burden for the host. So why do these plasmids exist and remain in bacteria? (more…)