I am interested in how this actually works. Is the bacterium sort of "aware" of the fact that its plasmid contains antibiotic resistance gene and therefore passes the plasmid to the other bacteria? What is the cellular mechanism that is used by plasmids to promote their transfer to other bacteria?
Dear colleague,
There are different mechanism of gene transfer in bacteria namely conjugation, transformation, and transduction .
During conjugation the genetic materials is transfer between bacterial cells by direct cell-to-cell contact or by a bridge-like connection between two cells. Donor cell produces pilus which attaches to recipient cell and brings the two cells together. Then the mobile plasmid is nicked and single strand of DNA is then transferred to the recipient cell. Both cells then synthesize a complementary strand to produce a double stranded circular plasmid and both become viable donors.
During transformation bacteria directly uptake, incorporate and express the exogenous genetic material from its surroundings through the cell membrane. During this a long double-stranded DNA molecule binds to the surface with the aid of a DNA-binding protein and is nicked by a nuclease . One strand is degraded by the nuclease and the undegraded strand associates with a competence-specific protein .The single strand then enters the cell and is integrated into the host chromosome in place of the homologous region of the host DNA.
And during the transduction genetic material is transferred from one bacterium to another by a virus (bacteriophage). After the phage has infected a bacterial cell, one of the newly forming phage particles picks up a bacterial DNA segment and when this phage particle infects another cell, it injects its bacterial DNA thereby adding additional traits to new bacteria.
Regards
Saroj
Dear colleague Paolo,
Normally I don´t write comments here because we can find many expertises much better than me to clarify our doubts. However, I would like to contribute with your request reinforcing the explanation made by Saroj, but I would like to highlight the participation of all genetic mobile elements, including plasmids, in the event of the antibiotic resistance. Sincerely yours, Silvana.
Dear Paolo,
Saroj and Maria explained it quiet well. I would like to mention that, not only antibiotic genes all the genes present in the plasmid can transfer via mobile gene transfer mechanisms.
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