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conjugative - mediate DNA transfer through conjugation and therefore spread rapidly among the bacterial cells of a population; e.g., F plasmid, many R and some col plasmids. nonconjugative - do not mediate DNA through conjugation, e.g., many R and col plasmids. The pBR322 plasmid is one of the first plasmids widely used as a cloning vector.
Animal Farm is a satirical allegorical novella, in the form of a beast fable, [1] by George Orwell, first published in England on 17 August 1945. [2] [3] It tells the story of a group of anthropomorphic farm animals who rebel against their human farmer, hoping to create a society where the animals can be equal, free, and happy.
In 1976, Robert A. Zakharyan reported the presence of a plasmid in a strain of B. thuringiensis and suggested the plasmid's involvement in endospore and crystal formation. [14] [15] B. thuringiensis is closely related to B. cereus, a soil bacterium, and B. anthracis, the cause of anthrax; the three organisms differ mainly in their plasmids.
The downside, however, is the low yield of product in comparison to prokaryotic vectors as well as the costly nature of the techniques involved. Its complicated technology, and potential contamination with animal viruses of mammalian cell expression have also placed a constraint on its use in large-scale industrial production. [37]
The term plasmid was coined in 1952 by the American molecular biologist Joshua Lederberg to refer to "any extrachromosomal hereditary determinant." [14] [15] 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 ...
Plasmids are almost always purified from liquid bacteria cultures, usually E. coli, which have been transformed and isolated. [5] [6] Virtually all plasmid vectors in common use encode one or more antibiotic resistance genes as a selectable marker, for example a gene encoding ampicillin or kanamycin resistance, which allows bacteria that have been successfully transformed to multiply uninhibited.
A plasmid partition system is a mechanism that ensures the stable inheritance of plasmids during bacterial cell division. Each plasmid has its independent replication system which controls the number of copies of the plasmid in a cell. The higher the copy number, the more likely the two daughter cells will contain the plasmid.
In molecular biology, a cryptic plasmid is a plasmid that doesn't appear to provide any clear advantage to its host, yet still persists in bacterial populations. [1] These plasmids appear to lack any genetic functions of interest and do not seem to contain genes that could provide beneficial functions to their hosts.