Biologicial functions of bacterial toxin-antitoxins systems

Toxin-antitoxin (TA) systems are small genetic modules that are widespread in prokaryotes. While initially discovered on plasmids, which they stabilize, TA systems are also abundantly found on bacterial chromosomes. Their functions are highly debated and have been examined in this thesis. First, we show that TA systems do not seem to play a role in stress response or antibiotic tolerance, as previously reported in the literature. Secondly, our single cell experiments demonstrate that the activation of TA systems promotes cell death in cells when a TA-encoding plasmid is lost, indicating that TA activation leads to death and not to a state of stress tolerance. We therefore conclude that TA systems are addictive genes that promote their own retention and that of the genetic elements that encode them.Doctorat en Sciences