title: Diversity of bacterial type II toxin-antitoxin systems: a comprehensive search and functional analysis of novel families.
abstract: Type II toxin-antitoxin (TA) systems are generally composed of two genes organized in an operon, encoding a labile antitoxin and a stable toxin. They were first discovered on plasmids where they contribute to plasmid stability by a phenomenon denoted as 'addiction', and subsequently in bacterial chromosomes. To discover novel families of antitoxins and toxins, we developed a bioinformatics approach based on the 'guilt by association' principle. Extensive experimental validation in Escherichia coli of predicted antitoxins and toxins increased significantly the number of validated systems and defined novel toxin and antitoxin families. Our data suggest that toxin families as well as antitoxin families originate from distinct ancestors that were assembled multiple times during evolution. Toxin and antitoxin families found on plasmids tend to be promiscuous and widespread, indicating that TA systems move through horizontal gene transfer. We propose that due to their addictive properties, TA systems are likely to be maintained in chromosomes even though they do not necessarily confer an advantage to their bacterial hosts. Therefore, addiction might play a major role in the evolutionary success of TA systems both on mobile genetic elements and in bacterial chromosomes.
authors.affiliation: Laboratoire de Bioinformatique des Génomes et des Réseaux (BiGRe), Faculté des Sciences, Université Libre de Bruxelles, Bld du Triomphe, 1050 Bruxelles, Belgium.
authors.forename: Raphaël
authors.initials: R
authors.lastname: Leplae
authors.forename: Damien
authors.initials: D
authors.lastname: Geeraerts
authors.forename: Régis
authors.initials: R
authors.lastname: Hallez
authors.forename: Julien
authors.initials: J
authors.lastname: Guglielmini
authors.forename: Pierre
authors.initials: P
authors.lastname: Drèze
authors.forename: Laurence
authors.initials: L
authors.lastname: Van Melderen
mesh_terms: D001426:Bacterial Proteins / Q000145:classification / Q000235:genetics / Q000378:metabolism; D001427:Bacterial Toxins / Q000145:classification* / Q000235:genetics / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics; D019143:Evolution, Molecular; D014644:Genetic Variation; D016680:Genome, Bacterial; D023281:Genomics
chemical_list: D001426:Bacterial Proteins; D001427:Bacterial Toxins