Plasmids are extrachromosomal, double standard, circular, self-replicating DNA molecules. Almost all the bacteria have plasmids containing a low copy number (1-4 per cell) or a high copy number (10-100 per cell). The size of plasmids varies from 1 to 500 kb. Usually, plasmids contribute to about 0.5 to 5.0% of the total DNA of bacteria.
Example:
Streptomyces sp.
A plasmid is a naturally occurring extrachromosomal double stranded DNA, circular DNA.
It replicates autonomously within bacterial cell.
Plasmid carries an origin of replication.
Plasmid vectors are the simplest cloning vectors.
It is most widely used for gene cloning.
Characteristics of Plasmid vector:
It contains an origin of replication.
It also Contain selective marker such as antibiotic resistance, blue white screening).
Small in size (1.0 to 250kb)
Contains multiple cloning site.
Easily isolated from the host cell.
Examples of plasmid vectors are:
pBR322
pUC 18/19
pBR322 vector
It is one of the first vectors to be developed by Boliver and Rodriguez in 1977.
in this concept following details will be covered.
Types of cloning vectors, plasmids, Bacteriophages, cosmids, phasmids, lamda
Different types of plasmids
Fertility plasmids
Resistance plasmids
Col plasmids
Degradative plasmids
Virulence plasmids
Conjugative plasmids
Non Conjugative plasmids
Stringent plasmids
Relaxed plasmids
pbr322
puc19
Plasmid applications
applications of Bacteriophages
types of vectors:
PLASMIDS
BACTERIOPHAGES
COSMIDS
Degradative Plasmids
Degradative plasmids help the host bacterium to digest compounds that are not commonly found in nature, such as camphor, xylene, toluene, and salicylic acid. These plasmids contain genes for special enzymes that break down specific compounds. Degradative plasmids are conjugative.
Virulence Plasmids
When a virulence plasmid is inside a bacterium, it turns that bacterium into a pathogen, which is an agent of disease. Bacteria that cause disease can be easily spread and replicated among affected individuals. The bacterium Escherichia coli (E. coli) has several virulence plasmids. E. coli is found naturally in the human gut and in other animals, but certain strains of E. coli can cause severe diarrhea and vomiting. Salmonella enterica is another bacterium that contains virulence plasmids.
