Classes of plasmids:
a) Virulence plasmid
b) Drug resistance plasmid
c) Encode gene for bacterial conjugation.
Effects of plasmid on host phenotype
- F factor: Increases fertility.
- R factor: Increases resistance to antibiotics
- Ti factor: Induce tumor in plants.
Important characteristics of normally occurring plasmids
a) Influence characteristics of their bacterial hosts.
b) Replicate independently the main chromosome.
c) Usually specific to one or a few species of bacteria.
d) Undergo reversible integration into bacterial chromosome.
e) Can be transferred by conjugation
f) Usually contain upto 40 genes
g) Don’t occur free in nature.