1. F and F– Plasmids: Plasmids that transfer genetic material from one bacterial cell to another are called F plasmids. Plasmid which helps in sexual reproduction by forming pili in bacterial cells is called F © plasmid.
2. R Plasmid: Plasmids that contain antibiotic resistance genes are called R plasmids. R6 plasmid is resistant to 6 important antibiotics. It is a gene marker. It contains the tetracycline antibiotic resistance gene.
3. Col Plasmid: Plasmids that produce a toxic protein called colicin are called Col plasmids. Colicin can kill susceptible E. coli cells. Plasmids contain genes producing vibriocin. Vibriocin can kill susceptible Vibrio cholerae cells.
4. Virulence Plasmid: Plasmids that cause disease are called virulence plasmids. Ti plasmid of Agrobacterium tumefaciens causes crown gall disease in dicotyledonous plants.
5. Degradative Plasmids: Plasmids which can rapidly convert the abnormal substances of bacteria like toluene, salicylic acid etc. are called degradative plasmids.