#Plasmid #Types #Stringent #Relaxed plasmid #Conjugativeplasmid
#Nonconjugativeplasmid #ColPlasmid #ResistantPlasmid #FertilityPlasmid #MetabolicPlasmid #VirulencePlasmid #ReplicationofPlasmid
#Sizeofplasmid #Copyno.ofplasmid #Typesofplasmid #Copynumber
#MajorBacterialPlasmid #MicrobialGenetics #English #TopLecture #ConceptualMicrobiologist #English
Plasmid is an extra chromosomal dsDNA molecules which replicates independently, so many bacteria have plasmid & are present in nucleoid region. They are usually more than one in numbers either circular or sometime in linear form. For example Bacillus burgdorferi bacteria carry 12 linear & 9 circular plasmid. But most known plasmid are circular Plasmid. plasmid have less genes than 30 generally & have no direct role in survival. Also plasmid carry many genes that give resistant to a bacterium in certain environment or harsh condition. & plasmid have many functions for example antibiotic resistance , nodule formation , & nitrogen fixation.
The term plasmid was first introduce by American molecular biologist Joshua Laderberg in 1952.
Plasmid use host cell machinery for replication . Usually Small size plasmid use host cell machinery for replication while large size plasmid use its own enzymes for replication. & some of the plasmid can integrated into chromosomes and are celled episomes. The plasmid transferred or inherited during cell division but some times they are not equally transferred to daughter cells or lost so the loss of plasmid is called Curing. Plasmid size ranges from 1 kb to 200 kb. Where small plasmid are considered as desire plasmid in genetic engineering.
Plasmid numbers varies from 1 to 50 copies / cell. Amplification of Plasmid is copy number of plasmid could be increased when the bacteria are in its
Exponential phase. The chloramphenicol stop chromosomal DNA from replication. When Add chloramphenicol then incubate for 12 hours plasmid will replicate and thousands copies of plasmid.
Types of plasmid based on copy numbers
1.Relaxed plasmid
2.Stringent plasmid
3.Conjugative plasmid
4.Non conjugative plasmid
Major Types of Bacterial Plasmid
a) Fertility 0R Conjugative plasmid
b) Resistant plasmid
c) Col Plasmid
d) Virulence Plasmid
e) Metabolic Plasmid
