Bacterial Pheromone for Sex and Abstinence

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Science  11 Nov 2005:
Vol. 310, Issue 5750, pp. 947
DOI: 10.1126/science.310.5750.947b

Bacteria can transfer DNA through conjugation, and the transfer of these extrachromosomal elements contributes to virulence and antibiotic resistance. Chandler et al. report that in Enterococcus faecalis, a mammalian pathogen, the same pheromone that stimulates a donor bacterium to initiate conjugation with a plasmid-free recipient is also produced by the donor itself and regulates its sensitivity to the recipient-produced pheromone. The bacterial chromosome encodes the pheromone (cCF10), so both donor and recipient can produce this molecule; to prevent conjugation with other donors, donor cells have two mechanisms for suppressing the response to the endogenously produced pheromone. One of the conjugation inhibitors is a secreted inhibitor protein, iCF10, which binds and sequesters secreted cCF10, and another is the membrane protein PrgY, which degrades or binds cCF10 as it is released. Using mutant bacterial strains that lacked functional cCF10, Chandler et al. show that cCF10 produced by the donor cells stimulates the production of iCF10. Donor cells grown in human plasma or in vivo also produce the plasmid-encoded aggregation factor Asc10, which contributes to cellular invasion and virulence of the bacteria. Albumin was identified as the plasma protein that bound iCF10, thereby shifting the balance between iCF10 and cCF10, allowing self-induction of the conjugation genes, including the one encoding Asc10. — NRG

Proc. Natl. Acad. Sci. U.S.A. 102, 15617 (2005).

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