Toxin-Antitoxin (TA) systems are common bipartite operons in prokaryotes. TA systems are composed of two genes adjacent to one another in which one encodes a protein toxic to the bacteria while the later provides the antitoxin. While TA systems are not well understood they have been implicated in phage resistance, biofilm production and persister cell formation which helps bacteria survive antibiotics and cause recurrent infection. One such system, PasTI, has been shown to be important for Extraintestinal pathogenic Escherichia coli (ExPEC) survival in the kidney and bladder and promotes the formation of persister cells when exposed to antibiotics. To better understand the pasTI system, strains lacking the TA operon were grown under oxidative and nitrosative stress conditions and shown to respond significantly worse than wild-type E. coli. Additionally pasT clones from other bacterial species with different pasT N-termini sequences: Y. pestis and N. meningitidis, were generated. When expression of PasT was induced in these clones and the wild-type, only the wild-type pasT proved to be toxic to the cell. Meanwhile, the clones continued to grow to an equal or better level than the wild-type. The clones also responded to stress conditions to equal or greater than wild-type abilities. Together the results suggest that the pasTI TA system plays a role in bacterial persistence and stress response and that the toxic effects observed in E. coli are the result of the N-terminal domain of the protein while differences in this protein region appear to relieve the toxicity of PasT while maintaining persistance and stress resistance abilities. The PasT protein's ability to aid in stress response and persistance could make it a target for antibiotic therapies against ExPEC and other pathogenic prokarya that have the gene.