A Toxin–Antitoxin System Promotes the Maintenance of an Integrative Conjugative Element

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A Toxin–Antitoxin System Promotes the Maintenance of an Integrative Conjugative Element

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Title: A Toxin–Antitoxin System Promotes the Maintenance of an Integrative Conjugative Element
Author: Wozniak, Rachel A. F.; Waldor, Matthew K

Note: Order does not necessarily reflect citation order of authors.

Citation: Wozniak, Rachel A. F., and Matthew K. Waldor. 2009. A toxin–antitoxin system promotes the maintenance of an integrative conjugative element. PLoS Genetics 5(3): e1000439.
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Abstract: SXT is an integrative and conjugative element (ICE) that confers resistance to multiple antibiotics upon many clinical isolates of Vibrio cholerae. In most cells, this ∼100 Kb element is integrated into the host genome in a site-specific fashion; however, SXT can excise to form an extrachromosomal circle that is thought to be the substrate for conjugative transfer. Daughter cells lacking SXT can theoretically arise if cell division occurs prior to the element's reintegration. Even though ∼2% of SXT-bearing cells contain the excised form of the ICE, cells that have lost the element have not been detected. Here, using a positive selection-based system, SXT loss was detected rarely at a frequency of ∼1×10−7. As expected, excision appears necessary for loss, and factors influencing the frequency of excision altered the frequency of SXT loss. We screened the entire 100 kb SXT genome and identified two genes within SXT, now designated mosA and mosT (for maintenance of SXT Antitoxin and Toxin), that promote SXT stability. These two genes, which lack similarity to any previously characterized genes, encode a novel toxin-antitoxin pair; expression of mosT greatly impaired cell growth and mosA expression ameliorated MosT toxicity. Factors that promote SXT excision upregulate mosAT expression. Thus, when the element is extrachromosomal and vulnerable to loss, SXT activates a TA module to minimize the formation of SXT-free cells.
Published Version: doi:10.1371/journal.pgen.1000439
Other Sources: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2654960/pdf/
Terms of Use: This article is made available under the terms and conditions applicable to Other Posted Material, as set forth at http://nrs.harvard.edu/urn-3:HUL.InstRepos:dash.current.terms-of-use#LAA
Citable link to this page: http://nrs.harvard.edu/urn-3:HUL.InstRepos:4853423

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