title: Type II Toxin-Antitoxin Systems in the Unicellular Cyanobacterium Synechocystis sp. PCC 6803.
abstract: Bacterial toxin-antitoxin (TA) systems are genetic elements, which are encoded by plasmid as well as chromosomal loci. They mediate plasmid and genomic island maintenance through post-segregational killing mechanisms but may also have milder effects, acting as mobile stress response systems that help certain cells of a population in persisting adverse growth conditions. Very few cyanobacterial TA system have been characterized thus far. In this work, we focus on the cyanobacterium Synechocystis 6803, a widely used model organism. We expand the number of putative Type II TA systems from 36 to 69 plus seven stand-alone components. Forty-seven TA pairs are located on the chromosome and 22 are plasmid-located. Different types of toxins are associated with various antitoxins in a mix and match principle. According to protein domains and experimental data, 81% of all toxins in Synechocystis 6803 likely exhibit RNase activity, suggesting extensive potential for toxicity-related RNA degradation and toxin-mediated transcriptome remodeling. Of particular interest is the Ssr8013-Slr8014 system encoded on plasmid pSYSG, which is part of a larger defense island or the pSYSX system Slr6056-Slr6057, which is linked to a bacterial ubiquitin-like system. Consequently, Synechocystis 6803 is one of the most prolific sources of new information about these genetic elements.
authors.affiliation: Faculty of Biology, Institute of Biology 3, Genetics and Experimental Bioinformatics, University of Freiburg, Sch&#228;nzlestr. 1, D-79104 Freiburg, Germany. stefan.kopfmann@gmx.de.
authors.forename: Stefan
authors.initials: S
authors.lastname: Kopfmann
authors.affiliation: Faculty of Biology, Institute of Biology 3, Genetics and Experimental Bioinformatics, University of Freiburg, Sch&#228;nzlestr. 1, D-79104 Freiburg, Germany. steffi-roesch@gmx.de.
authors.forename: Stefanie K
authors.initials: SK
authors.lastname: Roesch
authors.affiliation: Faculty of Biology, Institute of Biology 3, Genetics and Experimental Bioinformatics, University of Freiburg, Sch&#228;nzlestr. 1, D-79104 Freiburg, Germany. wolfgang.hess@biologie.uni-freiburg.de.
authors.forename: Wolfgang R
authors.initials: WR
authors.lastname: Hess
mesh_terms: D000992:Antitoxins / Q000235:genetics / Q000378:metabolism*; D001427:Bacterial Toxins / Q000235:genetics / Q000378:metabolism*; D002876:Chromosomes, Bacterial; D015964:Gene Expression Regulation, Bacterial; D015971:Gene Expression Regulation, Enzymologic; D000072417:Protein Domains; D020871:RNA Stability; D012329:RNA, Bacterial / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D012260:Ribonucleases / Q000235:genetics / Q000378:metabolism*; D013329:Structure-Activity Relationship; D046939:Synechocystis / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D013997:Time Factors
chemical_list: D000992:Antitoxins; D001427:Bacterial Toxins; D012329:RNA, Bacterial; D012333:RNA, Messenger; D012260:Ribonucleases
keywords: PIN-domain; RNA degradation; RNA interferase; RNA turnover; VapC; bacterial toxins; cibonuclease; cyanobacteria; hydrogenase; toxin–antitoxin