Plasmids and types

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 DNA technology or genetic engineering.

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…