Un plásmido es un fragmento intracelular separada de ADN[1] que puede replicarse independientemente del ADN cromosómico dentro de una célula. plasmids are found primarily in bacteria, but may be present occasionally in archaea and eukaryotes. Plasmids are generally circular DNA molecules.[2] Unlike the chromosomal DNA of bacteria, plasmids are typically not essential for bacterial growth.[2] Plasmids provide an important additional dimension towards the flexibility of the body's response to changes in their environment, whether those changes are hostile or potentially favorable.[3]