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Journal of Bacteriology, June 2005, p. 3620-3629, Vol. 187, No. 11
0021-9193/05/$08.00+0     doi:10.1128/JB.187.11.3620-3629.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

Vibrio fischeri Uses Two Quorum-Sensing Systems for the Regulation of Early and Late Colonization Factors

Claudia Lupp{dagger} and Edward G. Ruby*

Pacific Biomedical Research Center, University of Hawaii at Manoa, Honolulu, Hawaii

Received 14 December 2004/ Accepted 2 March 2005

Vibrio fischeri possesses two quorum-sensing systems, ain and lux, using acyl homoserine lactones as signaling molecules. We have demonstrated previously that the ain system activates luminescence gene expression at lower cell densities than those required for lux system activation and that both systems are essential for persistent colonization of the squid host, Euprymna scolopes. Here, we asked whether the relative contributions of the two systems are also important at different colonization stages. Inactivation of ain, but not lux, quorum-sensing genes delayed initiation of the symbiotic relationship. In addition, our data suggest that lux quorum sensing is not fully active in the early stages of colonization, implying that this system is not required until later in the symbiosis. The V. fischeri luxI mutant does not express detectable light levels in symbiosis yet initiates colonization as well as the wild type, suggesting that ain quorum sensing regulates colonization factors other than luminescence. We used a recently developed V. fischeri microarray to identify genes that are controlled by ain quorum sensing and could be responsible for the initiation defect. We found 30 differentially regulated genes, including the repression of a number of motility genes. Consistent with these data, ain quorum-sensing mutants displayed an altered motility behavior in vitro. Taken together, these data suggest that the sequential activation of these two quorum-sensing systems with increasing cell density allows the specific regulation of early colonization factors (e.g., motility) by ain quorum sensing, whereas late colonization factors (e.g., luminescence) are preferentially regulated by lux quorum sensing.


* Corresponding author. Present address: Department of Medical Microbiology and Immunology, 1300 University Ave., University of Wisconsin, Madison, WI 53706-1532. Phone: (608) 262-5911. Fax: (608) 262-8418. E-mail: egruby{at}wisc.edu.

{dagger} Present address: Michael Smith Laboratories, 301-2185 East Mall, The University of British Columbia, Vancouver, BC V6T 1Z4, Canada.


Journal of Bacteriology, June 2005, p. 3620-3629, Vol. 187, No. 11
0021-9193/05/$08.00+0     doi:10.1128/JB.187.11.3620-3629.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.




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