plasmids and types
TRANSCRIPT
Plasmids and its typesSijo.A
B.sc.Botany & Biotechnology
Mar ivanios college
Tvm, Kerala
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
DNA technology or genetic engineering.
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.
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.
3) Col plasmid(colicinogenic factors)
Col plasmid contains gene that produce some bacterial toxins.(bacteriocin).
Eg: colicin by E.coli, vibriocins by vibriocholerae.
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.
Thank you…