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author:("Wen, zhang T.")
1.  Characteristics of Biofilm Formation by Streptococcus mutans in the Presence of Saliva▿  
Infection and Immunity  2008;76(9):4259-4268.
Interactions between salivary agglutinin and the adhesin P1 of Streptococcus mutans contribute to bacterial aggregation and mediate sucrose-independent adherence to tooth surfaces. We have examined biofilm formation by S. mutans UA159, and derivative strains carrying mutations affecting the localization or expression of P1, in the presence of fluid-phase or adsorbed saliva or salivary agglutinin preparations. Whole saliva- and salivary agglutinin-induced aggregation of S. mutans was adversely affected by the loss of P1 and sortase (SrtA) but not by the loss of trigger factor (RopA). Fluid-phase salivary agglutinin and, to a lesser extent, immobilized agglutinin inhibited biofilm development by S. mutans in the absence of sucrose, and whole saliva was more effective at decreasing biofilm formation than salivary agglutinin. Inhibition of biofilm development by salivary agglutinin was differently influenced by particular mutations, with the P1-deficient strain displaying a greater inhibition of biofilm development than the SrtA- or RopA-deficient strains. As expected, biofilm-forming capacities of all strains in the presence of salivary preparations were markedly enhanced in the presence of sucrose, although biofilm formation by the mutants was less efficient than that by the parental strain. Aeration strongly inhibited biofilm development, and the presence of salivary components did not restore biofilm formation in aerated conditions. The results disclose a potent ability of salivary constituents to moderate biofilm formation by S. mutans through P1-dependent and P1-independent pathways.
PMCID: PMC2519434  PMID: 18625741
2.  Multilevel Control of Competence Development and Stress Tolerance in Streptococcus mutans UA159  
Infection and Immunity  2006;74(3):1631-1642.
Genetic competence appears to be important in establishment of biofilms and tolerance of environmental insults. We report here that the development of competence is controlled at multiple levels in a complex network that includes two signal-transducing two-component systems (TCS). Using Streptococcus mutans strain UA159, we demonstrate that the histidine kinase CiaH, but not the response regulator CiaR, causes a dramatic decrease in biofilm formation and in transformation efficiency. Inactivation of comE or comD had no effect on stress tolerance, but transformability of the mutants was poor and was not restored by addition of competence-stimulating peptide (CSP). Horse serum (HS) or bovine serum albumin (BSA) had no impact on transformability of any strains. Interestingly, though, the presence of HS or BSA in combination with CSP was required for efficient induction of comD, comX, and comYA, and induction was dependent on ComDE and CiaH, but not CiaR. Inactivation of comC, encoding CSP, had no impact on transformation, and CiaH was shown to be required for optimal comC expression. This study reveals that S. mutans integrates multiple environmental signals through CiaHR and ComDE to coordinate induction of com genes and that CiaH can exert its influence through CiaR and as-yet-unidentified regulators. The results highlight critical differences in the role and regulation of CiaRH and com genes in different S. mutans isolates and between S. mutans and Streptococcus pneumoniae, indicating that substantial divergence in the role and regulation of TCS and competence genes has occurred in streptococci.
PMCID: PMC1418624  PMID: 16495534
3.  Trigger Factor in Streptococcus mutans Is Involved in Stress Tolerance, Competence Development, and Biofilm Formation  
Infection and Immunity  2005;73(1):219-225.
Trigger factor is a ribosome-associated peptidyl-prolyl cis/trans isomerase that is highly conserved in most bacteria. A gene, designated ropA, encoding an apparent trigger factor homologue, was identified in Streptococcus mutans, the primary etiological agent of human dental caries. Inactivation of ropA had no major impact on growth rate in planktonic cultures under the conditions tested, although the RopA-deficient mutant formed long chains in broth. Deficiency of RopA decreased tolerance to acid killing and to oxidative stresses induced by hydrogen peroxide and paraquat, and it reduced transformation efficiency about 200-fold. Addition of synthetic competence-stimulating peptide to the culture medium enhanced transformability of both the mutant and wild-type strains, although the ropA strain did not attain levels of competence observed for the parent. Loss of RopA decreased the capacity of S. mutans to form biofilms by over 80% when cultivated in glucose, but it increased biofilm formation by over 50% when sucrose was provided as the carbohydrate source. Western blot analysis revealed that the expression of glucosyltransferases B and D was lower in the RopA-deficient mutant. These results suggest that RopA is a key regulator of acid and oxidative stress tolerance, genetic competence, and biofilm formation, all critical virulence properties of S. mutans.
PMCID: PMC538946  PMID: 15618157

Results 1-3 (3)