Autonomously replicating circular fragment present in DNA is called plasmids. The term plasmid was first introduced by American molecular biologist Joshua Lederberg in1952. An episome is a plasmid capable of inserting DNA into the host chromosome. Because of their ability to transfer DNA from one bacterium to another, plasmids are extensively used in recombinant DNA technology or genetic engineering.

1. Plasmids and its types
Sijo.A
B.sc.Botany & Biotechnology
Mar ivanios college
Tvm, Kerala

2. What are plasmids?
 Autonomously replicating circular
fragment present in DNA is called
plasmids.
 The term plasmid was first introduced
by American molecular biologist Joshua
Lederberg in1952.
 An episome is a plasmid capable of
inserting DNA into the host
chromosome.
 Because of their ability to transfer DNA
from one bacterium to another, plasmids
are extensively used in recombinant

3. classification
 Plasmids can be broadly classified into
conjugative plasmids and non-
conjugative plasmids.
 Conjugative plasmids contain a set of
transfer or tra genes which promote
sexual conjugation between different
cells.
 Non-conjugative plasmids are incapable
of initiating conjugation, hence they can
be transferred only with the assistance of
conjugative plasmids.
 An intermediate class of plasmids are
mobilizable. They promote their
conjugation by a helper plasmid.

4. Based on
function Based on function plasmids are classified
into five.
1) F plasmid(fertility factor)
 F plasmid contain tra genes which is
responsible for conjugation and result in
the expression of sex pili.
 F plasmids are actively involved in bacterial
conjugation, hence they are called
conjugation factors.
2) R plasmid(Resistance factor)
 R plasmid contains gene that provide
resistance against antibiotics and poisons.

5. 3) Col plasmid(colicinogenic factors)
 Col plasmid contains gene that produce
some bacterial toxins.(bacteriocin).
 Eg: colicin by E.coli, vibriocins by vibrio
cholerae.
4) metabolic or degradative plasmids
 Metabolic or degradative plasmids
contain a gene that produce some
metabolic enzymes.
 They can transmitted through
conjugation together with F plasmid.
5) virulente pathogen
 They contain gene which turn the
bacterium into a pathogen.

6.  Thank you…