Discovery of functional toxin/antitoxin systems in bacteria by shotgun cloning

Mol Cell. 2013 Apr 11;50(1):136-48. doi: 10.1016/j.molcel.2013.02.002. Epub 2013 Mar 7.


Toxin-antitoxin (TA) modules, composed of a toxic protein and a counteracting antitoxin, play important roles in bacterial physiology. We examined the experimental insertion of 1.5 million genes from 388 microbial genomes into an Escherichia coli host using more than 8.5 million random clones. This revealed hundreds of genes (toxins) that could only be cloned when the neighboring gene (antitoxin) was present on the same clone. Clustering of these genes revealed TA families widespread in bacterial genomes, some of which deviate from the classical characteristics previously described for such modules. Introduction of these genes into E. coli validated that the toxin toxicity is mitigated by the antitoxin. Infection experiments with T7 phage showed that two of the new modules can provide resistance against phage. Moreover, our experiments revealed an "antidefense" protein in phage T7 that neutralizes phage resistance. Our results expose active fronts in the arms race between bacteria and phage.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antitoxins / genetics*
  • Antitoxins / metabolism
  • Bacterial Toxins / genetics*
  • Bacterial Toxins / metabolism
  • Bacteriophage T7 / pathogenicity
  • Cloning, Molecular / methods*
  • Escherichia coli / genetics*
  • Escherichia coli / growth & development
  • Escherichia coli / metabolism
  • Escherichia coli / virology
  • Escherichia coli Proteins / genetics*
  • Escherichia coli Proteins / metabolism
  • Genome, Bacterial*
  • Host-Pathogen Interactions
  • Multigene Family
  • Reproducibility of Results
  • Sequence Analysis, DNA
  • Time Factors
  • Virulence


  • Antitoxins
  • Bacterial Toxins
  • Escherichia coli Proteins