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Journal of Bacteriology, January 2001, p. 451-460, Vol. 183, No. 2
Public Health Research Institute, New York,
New York 100161; Division of Applied
Microbiology, National Food Research Institute, Ministry of
Agriculture, Forestry and Fisheries, Kannondai 2-1-2, Tsukuba,
Ibaraki 305-8642, Japan2; and University
of Ljubljana, 1000 Ljubljana, Slovenia3
Received 10 August 2000/Accepted 17 October 2000
A quorum-sensing mechanism involving the pheromone ComX and the
ComP-ComA two-component system controls natural competence in
Bacillus subtilis. ComX is expressed as a cytoplasmic
inactive precursor that is released into the extracellular medium as a cleaved, modified decapeptide. This process requires the product of
comQ. In the presence of ComX, the membrane-localized ComP histidine kinase activates the response regulator ComA. We compared the
sequences of the quorum-sensing genes from four closely related bacilli, and we report extensive genetic polymorphism extending through
comQ, comX, and the 5' two-thirds of
comP. This part of ComP encodes the membrane-localized and
linker domains of the sensor protein. We also determined the sequences
of the comX genes of four additional wild-type bacilli and
tested the in vivo activities of all eight pheromones on isogenic
strains containing four different ComP receptor proteins. A striking
pattern of specificity was discovered, providing strong evidence that
the pheromone contacts ComP directly. Furthermore, we show that
coexpression of comQ and comX in
Escherichia coli leads to the production of active pheromone in the medium, demonstrating that comQ is the
only dedicated protein required for the processing, modification, and
release of active competence pheromone. Some of the implications of
these findings for the evolution and the mechanism of the
quorum-sensing system are discussed.
0021-9193/01/$04.00+0 DOI: 10.1128/JB.183.2.451-460.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Specificity and Genetic Polymorphism of the
Bacillus Competence Quorum-Sensing System


*
Corresponding author. Mailing address: Public Health
Research Institute, 455 First Ave., New York, NY 10016. Phone: (212) 578-0842. Fax: (212) 578-0804. E-mail:
dubnau{at}phri.nyu.edu.
Present address: Department of Molecular Biology and Microbiology,
Tufts University School of Medicine, 136 Harrison Ave., Boston, MA 02111.
Present address: University of Ljubljana, 1000 Ljubljana, Slovenia.
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