Toxin-antitoxin (TA) genetic modules have been found to widely exist in bacterial chromosomes and mobile genetic elements. They are composed of stable toxins and less stable antitoxins that can counteract the toxicity of toxins. The interactions between toxins and antitoxins could play critical roles in the virulence and persistence of pathogenic bacteria. There are at least eight types of TA systems which have been identified in a variety of bacteria. , a genus of Gram-negative bacteria, is widespread in aquatic environments and can cause various human diseases, such as epidemic cholera. In this review, we mainly explore the structures and functions of TA modules found in common pathogens, mainly , for better understanding of TA action mechanisms in pathogenic bacteria.