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Journal of Bacteriology, April 2009, p. 2060-2068, Vol. 191, No. 7
0021-9193/09/$08.00+0     doi:10.1128/JB.01609-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Role of Clp Proteins in Expression of Virulence Properties of Streptococcus mutans{triangledown} ,{dagger}

Jessica K. Kajfasz,1 Alaina R. Martinez,1 Isamar Rivera-Ramos,1,2 Jacqueline Abranches,1,2 Hyun Koo,1,3 Robert G. Quivey Jr.,1,2 and José A. Lemos1,2*

Center for Oral Biology,1 Department of Microbiology and Immunology,2 Eastman Department of Dentistry, University of Rochester Medical Center, Rochester, New York 146423

Received 12 November 2008/ Accepted 16 January 2009

Mutational analysis revealed that members of the Clp system, specifically the ClpL chaperone and the ClpXP proteolytic complex, modulate the expression of important virulence attributes of Streptococcus mutans. Compared to its parent, the {Delta}clpL strain displayed an enhanced capacity to form biofilms in the presence of sucrose, had reduced viability, and was more sensitive to acid killing. The {Delta}clpP and {Delta}clpX strains displayed several phenotypes in common: slow growth, tendency to aggregate in culture, reduced autolysis, and reduced ability to grow under stress, including acidic pH. Unexpectedly, the {Delta}clpP and {Delta}clpX mutants were more resistant to acid killing and demonstrated enhanced viability in long-term survival assays. Biofilm formation by the {Delta}clpP and {Delta}clpX strains was impaired when grown in glucose but enhanced in sucrose. In an animal study, the average number of S. mutans colonies recovered from the teeth of rats infected with the {Delta}clpP or {Delta}clpX strain was slightly lower than that of the parent strain. In Bacillus subtilis, the accumulation of the Spx global regulator, a substrate of ClpXP, has accounted for the {Delta}clpXP phenotypes. Searching the S. mutans genome, we identified two putative spx genes, designated spxA and spxB. The inactivation of either of these genes bypassed phenotypes of the clpP and clpX mutants. Western blotting demonstrated that Spx accumulates in the {Delta}clpP and {Delta}clpX strains. Our results reveal that the proteolysis of ClpL and ClpXP plays a role in the expression of key virulence traits of S. mutans and indicates that the underlying mechanisms by which ClpXP affect virulence traits are associated with the accumulation of two Spx orthologues.

* Corresponding author. Mailing address: Center for Oral Biology, Box 611, 601 Elmwood Ave., University of Rochester Medical Center, Rochester, NY 14642. Phone: (585) 275-1850. Fax: (585) 276-0190. E-mail: jose_lemos{at}urmc.rochester.edu

{triangledown} Published ahead of print on 30 January 2009.

{dagger} Supplemental material for this article may be found at http://jb.asm.org/.

Journal of Bacteriology, April 2009, p. 2060-2068, Vol. 191, No. 7
0021-9193/09/$08.00+0     doi:10.1128/JB.01609-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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