title: Conditional Activation of Toxin-Antitoxin Systems: Postsegregational Killing and Beyond.
abstract: Toxin-antitoxin (TA) systems are small genetic modules formed by a stable toxin and an unstable antitoxin that are widely present in plasmids and in chromosomes of Bacteria and Archaea. Toxins can interfere with cell growth or viability, targeting a variety of key processes. Antitoxin inhibits expression of the toxin, interacts with it, and neutralizes its effect. In a plasmid context, toxins are kept silent by the continuous synthesis of the unstable antitoxins; in plasmid-free cells (segregants), toxins can be activated owing to the faster decay of the antitoxin, and this results in the elimination of these cells from the population (postsegregational killing [PSK]) and in an increase of plasmid-containing cells in a growing culture. Chromosomal TA systems can also be activated in particular circumstances, and the interference with cell growth and viability that ensues contributes in different ways to the physiology of the cell. In this article, we review the conditional activation of TAs in selected plasmidic and chromosomal TA pairs and the implications of this activation. On the whole, the analysis underscores TA interactions involved in PSK and points to the effective contribution of TA systems to the physiology of the cell.
authors.affiliation: Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas, 28040 Madrid, Spain.
authors.forename: Ana María
authors.initials: AM
authors.lastname: Hernández-Arriaga
authors.affiliation: Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas, 28040 Madrid, Spain.
authors.forename: Wai Ting
authors.initials: WT
authors.lastname: Chan
authors.affiliation: Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas, 28040 Madrid, Spain.
authors.forename: Manuel
authors.initials: M
authors.lastname: Espinosa
authors.affiliation: Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas, 28040 Madrid, Spain.
authors.forename: Ramón
authors.initials: R
authors.lastname: Díaz-Orejas
mesh_terms: D001105:Archaea / Q000235:genetics* / Q000378:metabolism; D001419:Bacteria / Q000235:genetics* / Q000378:metabolism; D001692:Biological Transport; D002455:Cell Division; D005111:Extrachromosomal Inheritance; D050296:Microbial Viability; D010957:Plasmids / Q000378:metabolism*; D014118:Toxins, Biological / Q000037:antagonists & inhibitors* / Q000378:metabolism*
chemical_list: D014118:Toxins, Biological