Conjugation results in transfer of a part of the plasmid sequence and some portion of the bacterial chromosomal DNA. The transferred single-stranded DNA is recircularized and its complementary strand synthesized. The nick initiates rolling circle replication, and the displaced linear strand is directed to the recipient cell. Mobilization begins when a plasmid-encoded protein makes a single-stranded site-specific cleavage at the oriT. The DNA that is transferred by conjugation is not a double helix rather, it is a single-stranded molecule. If the F plasmid sequence is integrated into the bacterial chromosome, then the cell is designated as an Hfr (high-frequency recombination) cell. When it transfers into the recipient cell, it carries that fragment with it and converts it into an F′ male. If a fragment of chromosomal DNA has been incorporated into the plasmid, it is designated an F prime (F′) plasmid. On transfer of the F plasmid, the recipients become F + male cells. The sex pilus is a specialized type IV secretion device. The F plasmid is defined as conjugative because it carries all the genes necessary for its own transfer, including the ability to make sex pili and to initiate DNA synthesis at the transfer origin (oriT) of the plasmid. The mating type (sex) of the cell depends on the presence (male) or absence (female) of a conjugative plasmid, such as the F plasmid of E. Conjugation occurs with most, if not all, eubacteria and usually between members of the same or related species, but it also has been demonstrated to occur between prokaryotes and cells from plants, animals, and fungi. Murray PhD, F(AAM), F(IDSA), in Medical Microbiology, 2021 ConjugationĬonjugation results in one-way transfer of DNA from a donor (or male) cell to a recipient (or female) cell through the sex pilus.
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