Figure 1.

Schematic overview of type II and III Toxin-antitoxin (TA) system. The transcripts of TA system were expressed from the promoter of the operon. Toxin and antitoxin are defined as blue and red colors, respectively. The promoter is represented as a black box in the DNA. In type III system, antitoxin gene is separated with toxin gene by a Rho-independent terminator (represented as loop symbol) which regulate the toxin expression. Expressed toxin protein is neutralized by antitoxin protein (type II) or RNA (type III). When the external stimuli are applied, the toxin proteins are activated and degrade mRNA resulting in cell death.