> See also: > - Reference # Plasmids Plasmids are small, circular, double-stranded DNA molecules which occur naturally in certain bacterial cells. Technically a lot of bacteria can survive without plasmids - Conjugate plasmids - r plasmids: resistance - virulence plasmids: toxins - col plasmids: production of colicin proteins which have antibiotic activity and can kill other bacteria once integration occurs the bacterial chromosome becomes an episome ## Plasmids in Biotechnology Some species of bacteria are capable of sharing plasmids, and thus their genetic material, with nearby cells. This allows bacterial cells to *adapt* to new environments by receiving new plasmids and expressing them. This concept of sharing and receiving plasmids made researchers wonder if bacteria could also be made to uptake and expres