title: Toxins-antitoxins: diversity, evolution and function.
abstract: Genes for toxin-antitoxin (TA) complexes are widespread in prokaryote genomes, and species frequently possess tens of plasmid and chromosomal TA loci. The complexes are categorized into three types based on genetic organization and mode of action. The toxins universally are proteins directed against specific intracellular targets, whereas the antitoxins are either proteins or small RNAs that neutralize the toxin or inhibit toxin synthesis. Within the three types of complex, there has been extensive evolutionary shuffling of toxin and antitoxin genes leading to considerable diversity in TA combinations. The intracellular targets of the protein toxins similarly are varied. Numerous toxins, many of which are sequence-specific endoribonucleases, dampen protein synthesis levels in response to a range of stress and nutritional stimuli. Key resources are conserved as a result ensuring the survival of individual cells and therefore the bacterial population. The toxin effects generally are transient and reversible permitting a set of dynamic, tunable responses that reflect environmental conditions. Moreover, by harboring multiple toxins that intercede in protein synthesis in response to different physiological cues, bacteria potentially sense an assortment of metabolic perturbations that are channeled through different TA complexes. Other toxins interfere with the action of topoisomersases, cell wall assembly, or cytoskeletal structures. TAs also play important roles in bacterial persistence, biofilm formation and multidrug tolerance, and have considerable potential both as new components of the genetic toolbox and as targets for novel antibacterial drugs.
authors.affiliation: Faculty of Life Sciences and Manchester Interdisciplinary Biocentre, The University of Manchester, Manchester, UK. finbarr.hayes@manchester.ac.uk
authors.forename: Finbarr
authors.initials: F
authors.lastname: Hayes
authors.forename: Laurence
authors.initials: L
authors.lastname: Van Melderen
mesh_terms: D001419:Bacteria / Q000235:genetics* / Q000378:metabolism*; D001427:Bacterial Toxins / Q000737:chemistry / Q000145:classification* / Q000235:genetics*; D004722:Endoribonucleases / Q000737:chemistry / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D019143:Evolution, Molecular; D022761:Gene Transfer, Horizontal / Q000235:genetics; D016680:Genome, Bacterial; D008969:Molecular Sequence Data; D010957:Plasmids / Q000235:genetics*; D014176:Protein Biosynthesis; D014158:Transcription, Genetic
chemical_list: D001427:Bacterial Toxins; D004722:Endoribonucleases