IAI FigSearch
Home Help [Feedback] [For Subscribers] [Archive] [Search] [Contents]
This Article
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrowReprints and Permissions
Right arrow Copyright Information
Right arrow Books from ASM Press
Right arrow MicrobeWorld
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Fong, K. P.
Right arrow Articles by Demuth, D. R.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Fong, K. P.
Right arrow Articles by Demuth, D. R.

 Previous Article  |  Next Article 

Infection and Immunity, December 2001, p. 7625-7634, Vol. 69, No. 12
0019-9567/01/$04.00+0   DOI: 10.1128/IAI.69.12.7625-7634.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.

Intra- and Interspecies Regulation of Gene Expression by Actinobacillus actinomycetemcomitans LuxS

Karen P. Fong,1 Whasun O. Chung,2 Richard J. Lamont,2 and Donald R. Demuth1,*

Department of Biochemistry, School of Dental Medicine, University of Pennsylvania, Philadelphia, Pennsylvania,1 and Department of Oral Biology, University of Washington, Seattle, Washington2

Received 6 July 2001/Returned for modification 28 August 2001/Accepted 17 September 2001

The cell density-dependent control of gene expression is employed by many bacteria for regulating a variety of physiological functions, including the generation of bioluminescence, sporulation, formation of biofilms, and the expression of virulence factors. Although periodontal organisms do not appear to secrete acyl-homoserine lactone signals, several species, e.g., Porphyromonas gingivalis, Prevotella intermedia, and Fusobacterium nucleatum, have recently been shown to secrete a signal related to the autoinducer II (AI-2) of the signal system 2 pathway in Vibrio harveyi. Here, we report that the periodontal pathogen Actinobacillus actinomycetemcomitans expresses a homolog of V. harveyi luxS and secretes an AI-2-like signal. Cell-free conditioned medium from A. actinomycetemcomitans or from a recombinant Escherichia coli strain (E. coli AIS) expressing A. actinomycetemcomitans luxS induced luminescence in V. harveyi BB170 >200-fold over controls. AI-2 levels peaked in mid-exponential-phase cultures of A. actinomycetemcomitans and were significantly reduced in late-log- and stationary-phase cultures. Incubation of early-log-phase A. actinomycetemcomitans cells with conditioned medium from A. actinomycetemcomitans or from E. coli AIS resulted in a threefold induction of leukotoxic activity and a concomitant increase in leukotoxin polypeptide. In contrast, no increase in leukotoxin expression occurred when cells were exposed to sterile medium or to conditioned broth from E. coli AIS-, a recombinant strain in which luxS was insertionally inactivated. A. actinomycetemcomitans AI-2 also induced expression of afuA, encoding a periplasmic iron transport protein, approximately eightfold, suggesting that LuxS-dependent signaling may play a role in the regulation of iron acquisition by A. actinomycetemcomitans. Finally, A. actinomycetemcomitans AI-2 added in trans complemented a luxS knockout mutation in P. gingivalis by modulating the expression of the luxS-regulated genes uvrB and hasF in this organism. Together, these results suggest that LuxS-dependent signaling may modulate aspects of virulence and the uptake of iron by A. actinomycetemcomitans and induce responses in other periodontal organisms in mixed-species oral biofilm.

* Corresponding author. Mailing address: Room 540, Levy Research Building, Department of Biochemistry, School of Dental Medicine, University of Pennsylvania, 4010 Locust St., Philadelphia, PA 19014-6002. Phone: (215) 898-2125. Fax: (215) 898-3695. E-mail: demuth{at}biochem.dental.upenn.edu.

Infection and Immunity, December 2001, p. 7625-7634, Vol. 69, No. 12
0019-9567/01/$04.00+0   DOI: 10.1128/IAI.69.12.7625-7634.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.


This article has been cited by other articles:



Home Help [Feedback] [For Subscribers] [Archive] [Search] [Contents]
J. Bacteriol. J. Virol. Eukaryot. Cell
Microbiol. Mol. Biol. Rev. Clin. Vaccine Immunol. All ASM Journals

Copyright © 2001 by the American Society for Microbiology. All rights reserved.