Abstract:Toxin-antitoxin (TA) system is prevalent in chromosomes and mobile genetic elements of bacteria and archaea. TA systems are diverse in structure and function, which are currently classified into eight types (type I-VIII). They are involved in biofilm formation, virulence, drug-resistant infection of host bacteria, regulation of plasmid copy number, and maintenance of prophage after its excision. In this paper, we reviewed the latest classification and functions of TA systems and the regulatory functions of antitoxin, and then briefly described the application of TA systems.