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The term plasmid was coined in 1952 by the American molecular biologist Joshua Lederberg to refer to "any extrachromosomal hereditary determinant." [11] [12] The term's early usage included any bacterial genetic material that exists extrachromosomally for at least part of its replication cycle, but because that description includes bacterial viruses, the notion of plasmid was refined over time ...
A bacterial artificial chromosome (BAC) is a DNA construct, based on a functional fertility plasmid (or F-plasmid), used for transforming and cloning in bacteria, usually E. coli. [ 1 ] [ 2 ] [ 3 ] F-plasmids play a crucial role because they contain partition genes that promote the even distribution of plasmids after bacterial cell division.
Other cloning vectors include the pUC series of plasmids, and a large number of different cloning plasmid vectors are available. Many plasmids have high copy numbers, for example, pUC19 has a copy number of 500-700 copies per cell, [6] and high copy number is useful as it produces greater yield of recombinant plasmid for subsequent manipulation ...
Plasmids commonly carry a gene for antibiotic resistance that allows for the selection of bacterial cells containing the plasmid. Many plasmids also carry a reporter gene that allows researchers to distinguish clones containing an insert from those that do not. [3]
Various Azospirillum species possess seven replicons; A. lipoferum, for instance, has one bacterial chromosome, five chromids, and one plasmid. [4] Plasmids and bacteriophages are usually replicated as single replicons, but large plasmids in Gram-negative bacteria have been shown to carry several replicons.
[5] [1] [6] ParA proteins from different plasmids and bacterial species show 25 to 30% of sequence identity to the protein ParA of the plasmid P1. [7] The partition of type I system uses a "diffusion-ratchet" mechanism.
Since many R-factors contain F-plasmids, antibiotic resistance can be easily spread among a population of bacteria. [19] Also, R-factors can be taken up by "DNA pumps" in their membranes via transformation , [ 20 ] or less commonly through viral mediated transduction , [ 21 ] or via bacteriophage, although conjugation is the most common means ...
The DnaA-trio origin element is conserved in many bacterial species, indicating it is a key element for origin function. [70] After melting, the DUE provides an entry site for the E. coli replicative helicase DnaB, which is deposited onto each of the single DNA strands by its loader protein DnaC.