Novel Two-Component Regulatory System Involved in Biofilm Formation and Acid Resistance in

Dental Research Institute, University of Toronto, Ontario, Canada M5G 1G6.
Journal of Bacteriology (Impact Factor: 2.81). 12/2002; 184(22):6333-42. DOI: 10.1128/JB.184.22.6333-6342.2002
Source: PubMed


The abilities of Streptococcus mutans to form biofilms and to survive acidic pH are regarded as two important virulence determinants in the pathogenesis of dental
caries. Environmental stimuli are thought to regulate the expression of several genes associated with virulence factors through
the activity of two-component signal transduction systems. Yet, little is known of the involvement of these systems in the
physiology and pathogenicity of S. mutans. In this study, we describe a two-component regulatory system and its involvement in biofilm formation and acid resistance
in S. mutans. By searching the S. mutans genome database with tblastn with the HK03 and RR03 protein sequences from S. pneumoniae as queries, we identified two genes, designated hk11 and rr11, that encode a putative histidine kinase and its cognate response regulator. To gain insight into their function, a PCR-mediated
allelic-exchange mutagenesis strategy was used to create the hk11 (Emr) and rr11 (Emr) deletion mutants from S. mutans wild-type NG8 named SMHK11 and SMRR11, respectively. The mutants were examined for their growth rates, genetic competence,
ability to form biofilms, and resistance to low-pH challenge. The results showed that deletion of hk11 or rr11 resulted in defects in biofilm formation and resistance to acidic pH. Both mutants formed biofilms with reduced biomass (50
to 70% of the density of the parent strain). Scanning electron microscopy revealed that the biofilms formed by the mutants
had sponge-like architecture with what appeared to be large gaps that resembled water channel-like structures. The mutant
biofilms were composed of longer chains of cells than those of the parent biofilm. Deletion of hk11 also resulted in greatly diminished resistance to low pH, although we did not observe the same effect when rr11 was deleted. Genetic competence was not affected in either mutant. The results suggested that the gene product of hk11 in S. mutans might act as a pH sensor that could cross talk with one or more response regulators. We conclude that the two-component signal
transduction system encoded by hk11 and rr11 represents a new regulatory system involved in biofilm formation and acid resistance in S. mutans.

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    • "Smokers thus run a greater risk of contracting invasive diseases caused by various bacterial pathogens [30] [31] [32]. Exposure to cigarette smoke has also been shown to induce the formation of biofilm by various oral/respiratory pathogens in vitro, including P. gingivalis, S. aureus, S. pneumoniae, Klebsiella pneumonia, and P. aeruginosa, as well as Streptococcus mutans [30] [31] [32]. Cigarette smoke was also reported to increase C. albicans adhesion and growth, as well as biofilm formation [33] [34]. "
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    ABSTRACT: The predisposition of cigarette smokers for development of respiratory and oral bacterial infections is well documented. Cigarette smoke can also contribute to yeast infection. The aim of this study was to investigate the effect of cigarette smoke condensate (CSC) on C. albicans transition, chitin content, and response to environmental stress and to examine the interaction between CSC-pretreated C. albicans and normal human gingival fibroblasts. Following exposure to CSC, C. albicans transition from blastospore to hyphal form increased. CSC-pretreated yeast cells became significantly (P < 0.01) sensitive to oxidation but significantly (P < 0.01) resistant to both osmotic and heat stress. CSC-pretreated C. albicans expressed high levels of chitin, with 2- to 8-fold recorded under hyphal conditions. CSC-pretreated C. albicans adhered better to the gingival fibroblasts, proliferated almost three times more and adapted into hyphae, while the gingival fibroblasts recorded a significantly (P < 0.01) slow growth rate but a significantly higher level of IL-1β when in contact with CSC-pretreated C. albicans. CSC was thus able to modulate both C. albicans transition through the cell wall chitin content and the interaction between C. albicans and normal human gingival fibroblasts. These findings may be relevant to fungal infections in the oral cavity in smokers.
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    • "The identified species may improve dentistry by knowledge of their role in caries progression and pulpal inflammation (Schmidt et al., 2009). All these studies demonstrate that strains incapable of expressing determined proteins may have impaired growth in stressed conditions, and the discovery of a protein profile in different conditions may elucidate survival mechanisms of resistant microorganisms (Lemos and Burne, 2002; Li et al., 2002; Wilkins et al., 2002). "
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    ABSTRACT: Despite all the dental information acquired over centuries and the importance of proteome research, the cross-link between these two areas only emerged around mid-nineties. Proteomic tools can help dentistry in the identification of risk factors, early diagnosis, prevention, and systematic control that will promote the evolution of treatment in all dentistry specialties. This review mainly focuses on the evolution of dentistry in different specialties based on proteomic research and how these tools can improve knowledge in dentistry. The subjects covered are an overview of proteomics in dentistry, specific information on different fields in dentistry (dental structure, restorative dentistry, endodontics, periodontics, oral pathology, oral surgery, and orthodontics) and future directions. There are many new proteomic technologies that have never been used in dentistry studies and some dentistry areas that have never been explored by proteomic tools. It is expected that a greater integration of these areas will help to understand what is still unknown in oral health and disease. J. Cell. Physiol. 228: 2271-2284, 2013. © 2013 Wiley Periodicals, Inc.
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    • "With the deepening of the gingival pocket, the oxygen saturation of the crevice fluid decreases [15]. Many of the studies reported in the literature have been focused on the effect of acidification on the caries-causing Streptococcus mutans[16,17] ,and on its adhesion to hydroxyapatite, a bioceramic similar to the mineral component of bone and teeth [18]. An acidic pH of 4.5 has been shown to reduce the adhesion of S. mutans to hydroxyapatite, while a pH of 6.0 has been reported to have a similar effect on the ability of A. oris to adhere [19]. "
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    ABSTRACT: Background With the rising demand for osseointegrated titanium implants for replacing missing teeth, often in patients with a history of periodontitis, implant-related infections have become an issue of growing concern. Novel methods for treating and preventing implant-associated infections are urgently needed. The aim of this study was to investigate if different pH, atmosphere and surface properties could restrict bacterial adhesion to titanium surfaces used in dental implants. Methods Titanium discs with machined or anodized (TiUnite™) surface were incubated with a co-culture of Streptococcus mitis and Actinomyces oris (early colonizers of oral surfaces) at pH 5.0, 7.0 and 9.0 at aerobic or anaerobic atmosphere. The adhesion was analysed by counting colony forming (CFU) units on agar and by confocal laser scanning microscopy (CLSM). Results The CFU analysis showed that a pH of 5.0 was found to significantly decrease the adhesion of S. mitis, and an aerobic atmosphere, the adhesion of A. oris. S. mitis was found in significantly less amounts on the anodized surface than the machined surface, while A. oris was found in equal amounts on both surfaces. The CLSM analysis confirmed the results from the CFU count and provided additional information on how the two oral commensal species adhered to the surfaces: mainly in dispersed clusters oriented with the groves of the machined surface and the pores of the anodized surface. Conclusions Bacterial adhesion by S. mitis and A. oris can be restricted by acidic pH and aerobic atmosphere. The anodized surface reduced the adhesion of S. mitis compared to the machined surface; while A. oris adhered equally well to the pores of the anodized surface and to the grooves of the machined surface. It is difficult to transfer these results directly into a clinical situation. However, it is worth further investigating these findings from an in vitro perspective, as well as clinically, to gain more knowledge of the effects acid pH and aerobic atmosphere have on initial bacterial adhesion.
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