Addiction module

Addiction modules are toxin-antitoxin systems. Each consists of a pair of genes that specify two components: a stable toxin and an unstable antitoxin that interferes with the lethal action of the toxin. Found first in E. coli on low copy number plasmids, addiction modules are responsible for a process called the postsegregational killing effect. When bacteria lose these plasmid(s) (or other extrachromosomal elements), the cured cells are selectively killed because the unstable antitoxin is degraded faster than the more stable toxin. The term "addiction" is used because the cell depends on the de novo synthesis of the antitoxin for cell survival. Thus, addiction modules are implicated in maintaining the stability of extrachromosomal elements.

Toxin–antitoxin systems, some of which are homologous to these extrachromosomal addiction modules, also occur in the chromosomes of many bacteria.

ee also

*hok/sok system, an example of addiction module

References

cite journal| last =Engelberg-Kulka
first = Hanna
authorlink =
coauthors = Gad Glaser
title =Addiction modules and programmed cell death and antideath in bacterial cultures
journal =Annual Review of Microbiology
volume =53
issue =
pages =43–70
publisher =Annual Reviews
date =October 1999
url =http://arjournals.annualreviews.org/doi/abs/10.1146/annurev.micro.53.1.43
doi =
id =
accessdate = 2007-06-20