Discussion
A competent bacterial cell is one that
Answer: B
Correct answer: is able to take up DNA from its surroundings
Competence is the physiological state in which a bacterial cell can take up naked DNA from its environment - the requirement for transformation. It arises naturally in a number of species, including Streptococcus pneumoniae, Bacillus subtilis, Haemophilus influenzae and Neisseria. In these it is a regulated developmental state, usually appearing at a particular point in growth and often controlled by quorum sensing, with dedicated surface machinery for binding and importing DNA. It can also be induced artificially, which is what makes routine cloning possible. Treatment with calcium chloride at low temperature followed by a brief heat shock renders E. coli competent, and electroporation - a short high-voltage pulse that transiently permeabilises the membrane - achieves higher efficiency still. Competence is unrelated to conjugation, which requires the F plasmid, and to lysogeny, which requires an integrated prophage.
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