Enterococcus faecalis Senses Target Cells and in Response Expresses Cytolysin

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Science  24 Dec 2004:
Vol. 306, Issue 5705, pp. 2270-2272
DOI: 10.1126/science.1103996

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Many virulent strains of Enterococcus faecalis produce a two-subunit toxin, termed cytolysin. Cytolysin expression is regulated by one of the subunits (CylLS″) through a quorum-sensing autoinduction mechanism. We found that when target cells are absent, the other subunit (CylLL″) forms a complex with CylLS″, blocking it from autoinducing the operon. When target cells are present, however, CylLL″ binds preferentially to the target, allowing free CylLS″ to accumulate above the induction threshold. Thus, enterococci use CylLL″ to actively probe the environment for target cells, and when target cells are detected, allows the organism to express high levels of cytolysin in response.

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