Glycosyltransferase-Mediated Biofilm Matrix Dynamics and Virulence ofStreptococcus mutans

ABSTRACTStreptococcus mutansis a key cariogenic bacterium responsible for the initiation of tooth decay. Biofilm formation is a crucial virulence property. We discovered a putative glycosyltransferase, SMU_833, inS. mutanscapable of modulating dynamic interactions between two key biofilm matrix components, glucan and extracellular DNA (eDNA). The deletion ofsmu_833decreases glucan and increases eDNA but maintains the overall biofilm biomass. The decrease in glucan is caused by a reduction in GtfB and GtfC, two key enzymes responsible for the synthesis of glucan. The increase in eDNA was accompanied by an elevated production of membrane vesicles, suggesting that SMU_833 modulates the release of eDNA via the membrane vesicles, thereby altering biofilm matrix constituents. Furthermore, glucan and eDNA were colocalized. The complete deletion ofgtfBCfrom thesmu_833mutant significantly reduced the biofilm biomass despite the elevated eDNA, suggesting the requirement of minimal glucans as a binding substrate for eDNA within the biofilm. Despite no changes in overall biofilm biomass, the mutant biofilm was altered in biofilm architecture and was less acidicin vitro. Concurrently, the mutant was less virulent in anin vivorat model of dental caries, demonstrating that SMU_833 is a new virulence factor. Taken together, we conclude that SMU_833 is required for optimal biofilm development and virulence ofS. mutansby modulating extracellular matrix components. Our study of SMU_833-modulated biofilm matrix dynamics uncovered a new target that can be used to develop potential therapeutics that prevent and treat dental caries.IMPORTANCETooth decay, a costly and painful disease affecting the vast majority of people worldwide, is caused by the bacteriumStreptococcus mutans. The bacteria utilize dietary sugars to build and strengthen biofilms, trapping acids onto the tooth’s surface and causing demineralization and decay of teeth. As knowledge of our body’s microbiomes increases, the need for developing therapeutics targeted to disease-causing bacteria has arisen. The significance of our research is in studying and identifying a novel therapeutic target, a dynamic biofilm matrix that is mediated by a new virulence factor and membrane vesicles. The study increases our understanding ofS. mutansvirulence and also offers a new opportunity to develop effective therapeutics targetingS. mutans. In addition, the mechanisms of membrane vesicle-mediated biofilm matrix dynamics are also applicable to other biofilm-driven infectious diseases.

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l-Arginine Modifies the Exopolysaccharide Matrix and Thwarts Streptococcus mutans Outgrowth within Mixed-Species Oral Biofilms

Journal of Bacteriology ◽

10.1128/jb.00021-16 ◽

2016 ◽

Vol 198 (19) ◽

pp. 2651-2661 ◽

Cited By ~ 41

Author(s):

Jinzhi He ◽

Geelsu Hwang ◽

Yuan Liu ◽

Lizeng Gao ◽

LaTonya Kilpatrick-Liverman ◽

...

Keyword(s):

Dental Caries ◽

Streptococcus Mutans ◽

Biological Properties ◽

Vehicle Control ◽

Microbial Interactions ◽

Mixed Species ◽

Matrix Assembly ◽

Content Type ◽

Biofilm Development ◽

Biofilm Matrix

ABSTRACTl-Arginine, a ubiquitous amino acid in human saliva, serves as a substrate for alkali production by arginolytic bacteria. Recently, exogenousl-arginine has been shown to enhance the alkalinogenic potential of oral biofilm and destabilize its microbial community, which might help control dental caries. However,l-arginine exposure may inflict additional changes in the biofilm milieu when bacteria are growing under cariogenic conditions. Here, we investigated how exogenousl-arginine modulates biofilm development using a mixed-species model containing both cariogenic (Streptococcus mutans) and arginolytic (Streptococcus gordonii) bacteria in the presence of sucrose. We observed that 1.5% (wt/vol)l-arginine (also a clinically effective concentration) exposure suppressed the outgrowth ofS. mutans, favoredS. gordoniidominance, and maintainedActinomyces naeslundiigrowth within biofilms (versus vehicle control). In parallel, topicall-arginine treatments substantially reduced the amounts of insoluble exopolysaccharides (EPS) by >3-fold, which significantly altered the three-dimensional (3D) architecture of the biofilm. Intriguingly,l-arginine repressedS. mutansgenes associated with insoluble EPS (gtfB) and bacteriocin (SMU.150) production, whilespxBexpression (H2O2production) byS. gordoniiincreased sharply during biofilm development, which resulted in higher H2O2levels in arginine-treated biofilms. These modifications resulted in a markedly defective EPS matrix and areas devoid of any bacterial clusters (microcolonies) on the apatitic surface, while thein situpH values at the biofilm-apatite interface were nearly one unit higher in arginine-treated biofilms (versus the vehicle control). Our data reveal new biological properties ofl-arginine that impact biofilm matrix assembly and the dynamic microbial interactions associated with pathogenic biofilm development, indicating the multiaction potency of this promising biofilm disruptor.IMPORTANCEDental caries is one of the most prevalent and costly infectious diseases worldwide, caused by a biofilm formed on tooth surfaces. Novel strategies that compromise the ability of virulent species to assemble and maintain pathogenic biofilms could be an effective alternative to conventional antimicrobials that indiscriminately kill other oral species, including commensal bacteria.l-Arginine at 1.5% has been shown to be clinically effective in modulating cariogenic biofilms via alkali production by arginolytic bacteria. Using a mixed-species ecological model, we show new mechanisms by whichl-arginine disrupts the process of biofilm matrix assembly and the dynamic microbial interactions that are associated with cariogenic biofilm development, without impacting the bacterial viability. These results may aid in the development of enhanced methods to control biofilms usingl-arginine.

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Symbiotic Relationship between Streptococcus mutans and Candida albicans Synergizes Virulence of Plaque BiofilmsIn Vivo

Infection and Immunity ◽

10.1128/iai.00087-14 ◽

2014 ◽

Vol 82 (5) ◽

pp. 1968-1981 ◽

Cited By ~ 216

Author(s):

Megan L. Falsetta ◽

Marlise I. Klein ◽

Punsiri M. Colonne ◽

Kathleen Scott-Anne ◽

Stacy Gregoire ◽

...

Keyword(s):

Candida Albicans ◽

Dental Caries ◽

Streptococcus Mutans ◽

Bacterial Pathogen ◽

Single Species ◽

Content Type ◽

3 Dimensional ◽

Biofilm Development

ABSTRACTStreptococcus mutansis often cited as the main bacterial pathogen in dental caries, particularly in early-childhood caries (ECC).S. mutansmay not act alone;Candida albicanscells are frequently detected along with heavy infection byS. mutansin plaque biofilms from ECC-affected children. It remains to be elucidated whether this association is involved in the enhancement of biofilm virulence. We showed that the ability of these organisms together to form biofilms is enhancedin vitroandin vivo. The presence ofC. albicansaugments the production of exopolysaccharides (EPS), such that cospecies biofilms accrue more biomass and harbor more viableS. mutanscells than single-species biofilms. The resulting 3-dimensional biofilm architecture displays sizeableS. mutansmicrocolonies surrounded by fungal cells, which are enmeshed in a dense EPS-rich matrix. Using a rodent model, we explored the implications of this cross-kingdom interaction for the pathogenesis of dental caries. Coinfected animals displayed higher levels of infection and microbial carriage within plaque biofilms than animals infected with either species alone. Furthermore, coinfection synergistically enhanced biofilm virulence, leading to aggressive onset of the disease with rampant carious lesions. Ourin vitrodata also revealed that glucosyltransferase-derived EPS is a key mediator of cospecies biofilm development and that coexistence withC. albicansinduces the expression of virulence genes inS. mutans(e.g.,gtfB,fabM). We also found thatCandida-derived β1,3-glucans contribute to the EPS matrix structure, while fungal mannan and β-glucan provide sites for GtfB binding and activity. Altogether, we demonstrate a novel mutualistic bacterium-fungus relationship that occurs at a clinically relevant site to amplify the severity of a ubiquitous infectious disease.

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Coordinated Regulation of the EIIMan and fruRKI Operons of Streptococcus mutans by Global and Fructose-Specific Pathways

Applied and Environmental Microbiology ◽

10.1128/aem.01403-17 ◽

2017 ◽

Vol 83 (21) ◽

Cited By ~ 6

Author(s):

Lin Zeng ◽

Brinta Chakraborty ◽

Tanaz Farivar ◽

Robert A. Burne

Keyword(s):

Energy Metabolism ◽

Dental Caries ◽

Streptococcus Mutans ◽

Regulation Of Gene Expression ◽

Phosphotransferase System ◽

Carbohydrate Source ◽

Content Type ◽

Fructose Metabolism ◽

Biofilm Development

ABSTRACTThe glucose/mannose-phosphotransferase system (PTS) permease EIIManencoded bymanLMNin the dental caries pathogenStreptococcus mutanshas a dominant influence on sugar-specific, CcpA-independent catabolite repression (CR). Mutations inmanLaffect energy metabolism and virulence-associated traits, including biofilm formation, acid tolerance, and competence. Using promoter::reporter fusions, expression of themanLMNand thefruRKIoperons, encoding a transcriptional regulator, a fructose-1-phosphate kinase and a fructose-PTS permease EIIFru, respectively, was monitored in response to carbohydrate source and in mutants lacking CcpA, FruR, and components of EIIMan. Expression of genes for EIIManand EIIFruwas directly regulated by CcpA and CR, as evinced byin vivoandin vitromethods. Unexpectedly, not only was thefruRKIoperon negatively regulated by FruR, but also so wasmanLMN. Carbohydrate transport by EIIManhad a negative influence on expression ofmanLMNbut notfruRKI. In agreement with the proposed role of FruR in regulating these PTS operons, loss offruRorfruKsubstantially altered growth on a number of carbohydrates, including fructose. RNA deep sequencing revealed profound changes in gene regulation caused by deletion offruKorfruR. Collectively, these findings demonstrate intimate interconnection of the regulation of two major PTS permeases inS. mutansand reveal novel and important contributions of fructose metabolism to global regulation of gene expression.IMPORTANCEThe ability ofStreptococcus mutansand other streptococcal pathogens to survive and cause human diseases is directly dependent upon their capacity to metabolize a variety of carbohydrates, including glucose and fructose. Our research reveals that metabolism of fructose has broad influences on the regulation of utilization of glucose and other sugars, and mutants with changes in certain genes involved in fructose metabolism display profoundly different abilities to grow and express virulence-related traits. Mutants lacking the FruR regulator or a particular phosphofructokinase, FruK, display changes in expression of a large number of genes encoding transcriptional regulators, enzymes required for energy metabolism, biofilm development, biosynthetic and degradative processes, and tolerance of a spectrum of environmental stressors. Since fructose is a major component of the modern human diet, the results have substantial significance in the context of oral health and the development of dental caries.

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Isolation of the Bacteriophages Inhibiting the Expression of the Genes Involved in Biofilm Formation by Streptococcus mutans

Jundishapur Journal of Microbiology ◽

10.5812/jjm.113206 ◽

2021 ◽

Vol 14 (1) ◽

Author(s):

Zahra Rajabi ◽

Rouha Kermanshahi ◽

Mohammad Mehdi Soltan Dallal ◽

Yousef Erfani ◽

Reza Ranjbar

Keyword(s):

Dental Caries ◽

Streptococcus Mutans ◽

Biofilm Formation ◽

Culture Media ◽

Bacterial Biofilm ◽

Tooth Decay ◽

Urban Sewage ◽

Molecular Tests ◽

Transmission Electron ◽

Biofilm Development

Background: The potential of Streptococcus mutans for biofilm formation makes it one of the main organisms causing dental caries. Various preventive strategies have been applied to reduce tooth decay. Objectives: In the current study, we aimed to isolate S. mutans bacteriophages from sewage and to investigate their effects on the expression of the genes involved in bacterial biofilm formation in dental caries. Methods: Eighty-one dental plaque samples were collected. Then to isolate and identify S. mutans, bacterial culture media and molecular tests were used. Moreover, the biofilm formation capability of the isolated S. mutans was determined. Also, lytic bacteriophages were isolated from raw urban sewage, and phage morphology was determined by transmission electron microscopy (TEM). Real-time PCR was used to assess the effects of the isolated bacteriophages on the expression of the genes involved in biofilm formation. Results: Overall, 32 (39.5%) samples were positive for the presence of S. mutans. All of the isolates contained the gtfD gene. The frequencies of other genes were as follows: gtfB (17, 53.12%), gtfC (19, 53.37%), SpaP (13, 40.62%), and luxS (23, 17.87%). The isolated S. mutans bacteria presented different ranges of biofilm formation ability. Based on TEM results, two sewage-isolated bacteriophages, belonging to Siphoviridae and Tectiviridae families, were able to prevent biofilm formation up to 97%. Conclusions: Our findings indicate that phage therapy can be an optional way for controlling biofilm development and reducing the colonization of teeth surface by S. mutans.

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Oxidative Stressors Modify the Response of Streptococcus mutans to Its Competence Signal Peptides

Applied and Environmental Microbiology ◽

10.1128/aem.01345-17 ◽

2017 ◽

Vol 83 (22) ◽

Cited By ~ 9

Author(s):

Matthew De Furio ◽

Sang Joon Ahn ◽

Robert A. Burne ◽

Stephen J. Hagen

Keyword(s):

Oxidative Stress ◽

Reactive Oxygen Species ◽

Dental Caries ◽

Signaling Pathway ◽

Streptococcus Mutans ◽

Reactive Oxygen ◽

Oxygen Species ◽

Oral Biofilm ◽

Genetic Competence ◽

Content Type

ABSTRACTThe dental caries pathogenStreptococcus mutansis continually exposed to several types of stress in the oral biofilm environment. Oxidative stress generated by reactive oxygen species has a major impact on the establishment, persistence, and virulence ofS. mutans. Here, we combined fluorescent reporter-promoter fusions with single-cell imaging to study the effects of reactive oxygen species on activation of genetic competence inS. mutans. Exposure to paraquat, which generates superoxide anion, produced a qualitatively different effect on activation of expression of the gene for the master competence regulator, ComX, than did treatment with hydrogen peroxide (H2O2), which can yield hydroxyl radical. Paraquat suppressed peptide-mediated induction ofcomXin a progressive and cumulative fashion, whereas the response to H2O2displayed a strong threshold behavior. Low concentrations of H2O2had little effect on induction ofcomXor the bacteriocin genecipB, but expression of these genes declined sharply if extracellular H2O2exceeded a threshold concentration. These effects were not due to decreased reporter gene fluorescence. Two different threshold concentrations were observed in the response to H2O2, depending on the gene promoter that was analyzed and the pathway by which the competence regulon was stimulated. The results show that paraquat and H2O2affect theS. mutanscompetence signaling pathway differently, and that some portions of the competence signaling pathway are more sensitive to oxidative stress than others.IMPORTANCEStreptococcus mutansinhabits the oral biofilm, where it plays an important role in the development of dental caries. Environmental stresses such as oxidative stress influence the growth ofS. mutansand its important virulence-associated behaviors, such as genetic competence.S. mutanscompetence development is a complex behavior that involves two different signaling peptides and can exhibit cell-to-cell heterogeneity. Although oxidative stress is known to influenceS. mutanscompetence, it is not understood how oxidative stress interacts with the peptide signaling or affects heterogeneity. In this study, we used fluorescent reporters to probe the effect of reactive oxygen species on competence signaling at the single-cell level. Our data show that different reactive oxygen species have different effects onS. mutanscompetence, and that some portions of the signaling pathway are more acutely sensitive to oxidative stress than others.

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Essential Roles of thesppRAFructose-Phosphate Phosphohydrolase Operon in Carbohydrate Metabolism and Virulence Expression byStreptococcus mutans

Journal of Bacteriology ◽

10.1128/jb.00586-18 ◽

2018 ◽

Vol 201 (2) ◽

Cited By ~ 1

Author(s):

Lin Zeng ◽

Robert A. Burne

Keyword(s):

Dental Caries ◽

Organic Acids ◽

Streptococcus Mutans ◽

Biochemical Characterization ◽

Constitutive Expression ◽

Extracellular Dna ◽

Tooth Surface ◽

Oral Diseases ◽

Sugar Phosphate ◽

Content Type

ABSTRACTThe dental caries pathogenStreptococcus mutanscan ferment a variety of sugars to produce organic acids. Exposure ofS. mutansto certain nonmetabolizable carbohydrates, such as xylitol, impairs growth and can cause cell death. Recently, the presence of a sugar-phosphate stress inS. mutanswas demonstrated using a mutant lacking 1-phosphofructokinase (FruK) that accumulates fructose-1-phosphate (F-1-P). Here, we studied an operon inS. mutans,sppRA, which was highly expressed in thefruKmutant. Biochemical characterization of a recombinant SppA protein indicated that it possessed hexose-phosphate phosphohydrolase activity, with preferences for F-1-P and, to a lesser degree, fructose-6-phosphate (F-6-P). SppA activity was stimulated by Mg2+and Mn2+but inhibited by NaF. SppR, a DeoR family regulator, repressed the expression of thesppRAoperon to minimum levels in the absence of the fructose-derived metabolite F-1-P and likely also F-6-P. The accumulation of F-1-P, as a result of growth on fructose, not only inducedsppAexpression, but it significantly altered biofilm maturation through increased cell lysis and enhanced extracellular DNA release. Constitutive expression ofsppA, via a plasmid or by deletingsppR, greatly alleviated fructose-induced stress in afruKmutant, enhanced resistance to xylitol, and reversed the effects of fructose on biofilm formation. Finally, by identifying three additional putative phosphatases that are capable of promoting sugar-phosphate tolerance, we show thatS. mutansis capable of mounting a sugar-phosphate stress response by modulating the levels of certain glycolytic intermediates, functions that are interconnected with the ability of the organism to manifest key virulence behaviors.IMPORTANCEStreptococcus mutansis a major etiologic agent for dental caries, primarily due to its ability to form biofilms on the tooth surface and to convert carbohydrates into organic acids. We have discovered a two-gene operon inS. mutansthat regulates fructose metabolism by controlling the levels of fructose-1-phosphate, a potential signaling compound that affects bacterial behaviors. With fructose becoming increasingly common and abundant in the human diet, we reveal the ways that fructose may alter bacterial development, stress tolerance, and microbial ecology in the oral cavity to promote oral diseases.

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Effects of pH on the Properties of Membrane Vesicles Including Glucosyltransferase in Streptococcus mutans

Microorganisms ◽

10.3390/microorganisms9112308 ◽

2021 ◽

Vol 9 (11) ◽

pp. 2308

Author(s):

Yusuke Iwabuchi ◽

Tomoyo Nakamura ◽

Yasuka Kusumoto ◽

Ryoma Nakao ◽

Tsutomu Iwamoto ◽

...

Keyword(s):

Streptococcus Mutans ◽

Biofilm Formation ◽

Membrane Vesicles ◽

Extracellular Dna ◽

Tooth Surface ◽

Initial Ph ◽

Effects Of Ph ◽

Low Levels ◽

Quantitative Changes ◽

Biofilm Development

Streptococcus mutans releases membrane vesicles (MVs) and induces MV-dependent biofilm formation. Glucosyltransferases (Gtfs) are bound to MVs and contribute to the adhesion and glucans-dependent biofilm formation of early adherent bacteria on the tooth surface. The biofilm formation of S. mutans may be controlled depending on whether the initial pH tends to be acidic or alkaline. In this study, the characteristics and effects of MVs extracted from various conditions {(initial pH 6.0 and 8.0 media prepared with lactic acid (LA) and acetic acid (AA), and with NaOH (NO), respectively)} on the biofilm formation of S. mutans and early adherent bacteria were investigated. The quantitative changes in glucans between primary pH 6.0 and 8.0 conditions were observed, associated with different activities affecting MV-dependent biofilm formation. The decreased amount of Gtfs on MVs under the initial pH 6.0 conditions strongly guided low levels of MV-dependent biofilm formation. However, in the initial pH 6.0 and 8.0 solutions prepared with AA and NO, the MVs in the biofilm appeared to be formed by the expression of glucans and/or extracellular DNA. These results suggest that the environmental pH conditions established by acid and alkaline factors determine the differences in the local pathogenic activities of biofilm development in the oral cavity.

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Synergism of Streptococcus mutans and Candida albicans Reinforces Biofilm Maturation and Acidogenicity in Saliva: An In Vitro Study

Frontiers in Cellular and Infection Microbiology ◽

10.3389/fcimb.2020.623980 ◽

2021 ◽

Vol 10 ◽

Author(s):

Hye-Eun Kim ◽

Yuan Liu ◽

Atul Dhall ◽

Marwa Bawazir ◽

Hyun Koo ◽

...

Keyword(s):

Candida Albicans ◽

Dental Caries ◽

Streptococcus Mutans ◽

Critical Role ◽

In Vitro Study ◽

Acidic Ph ◽

Acidic Environment ◽

Symbiotic Interaction ◽

Biofilm Development

Early childhood caries, a virulent-form of dental caries, is painful, difficult, and costly to treat that has been associated with high levels of Streptococcus mutans (Sm) and Candida albicans (Ca) in plaque-biofilms on teeth. These microorganisms appear to develop a symbiotic cross-kingdom interaction that amplifies the virulence of plaque-biofilms. Although biofilm studies reveal synergistic bacterial-fungal association, how these organisms modulate cross-kingdom biofilm formation and enhance its virulence in the presence of saliva remain largely unknown. Here, we compared the properties of Sm and Sm-Ca biofilms cultured in saliva by examining the biofilm structural organization and capability to sustain an acidic pH environment conducive to enamel demineralization. Intriguingly, Sm-Ca biofilm is rapidly matured and maintained acidic pH-values (~4.3), while Sm biofilm development was retarded and failed to create an acidic environment when cultured in saliva. In turn, the human enamel slab surface was severely demineralized by Sm-Ca biofilms, while there was minimal damage to the enamel surface by Sm biofilm. Interestingly, Sm-Ca biofilms exhibited an acidic environment regardless of their hyphal formation ability. Our data reveal the critical role of symbiotic interaction between S. mutans and C. albicans in human saliva in the context of pathogenesis of dental caries, which may explain how the cross-kingdom interaction contributes to enhanced virulence of plaque-biofilm in the oral cavity.

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Understanding the Basis of METH Mouth Using a Rodent Model of Methamphetamine Injection, Sugar Consumption, and Streptococcus mutans Infection

mBio ◽

10.1128/mbio.03534-20 ◽

2021 ◽

Vol 12 (2) ◽

Author(s):

Hiu Ham Lee ◽

Preethi Sudhakara ◽

Shreena Desai ◽

Kildare Miranda ◽

Luis R. Martinez

Keyword(s):

Streptococcus Mutans ◽

Biofilm Formation ◽

Human Saliva ◽

Tooth Decay ◽

Content Type ◽

Oral Rinse ◽

Tooth Grinding ◽

Oral Tissue ◽

Public Health Strategies ◽

The Impact

ABSTRACT “METH mouth” is a common consequence of chronic methamphetamine (METH) use, resulting in tooth decay and painful oral tissue inflammation that can progress to complete tooth loss. METH reduces the amount of saliva in the mouth, promoting bacterial growth, tooth decay, and oral tissue damage. This oral condition is worsened by METH users’ compulsive behavior, including high rates of consumption of sugary drinks, recurrent tooth grinding, and a lack of frequent oral hygiene. Streptococcus mutans is a Gram-positive bacterium found in the oral cavity and associated with caries in humans. Hence, we developed a murine model of METH administration, sugar intake, and S. mutans infection to mimic METH mouth in humans and to investigate the impact of this drug on tooth colonization. We demonstrated that the combination of METH and sucrose stimulates S. mutans tooth adhesion, growth, and biofilm formation in vivo. METH and sucrose increased the expression of S. mutans glycosyltransferases and lactic acid production. Moreover, METH contributes to the low environmental pH and S. mutans sucrose metabolism, providing a plausible mechanism for bacterium-mediated tooth decay. Daily oral rinse treatment with chlorhexidine significantly reduces tooth colonization in METH- and sucrose-treated mice. Furthermore, human saliva inhibits S. mutans colonization and biofilm formation after exposure to either sucrose or the combination of METH and sucrose. These findings suggest that METH might increase the risk of microbial dental disease in users, information that may help in the development of effective public health strategies to deal with this scourge in our society. IMPORTANCE “METH mouth” is characterized by severe tooth decay and gum disease, which often causes teeth to break or fall out. METH users are also prone to colonization by cariogenic bacteria such as Streptococcus mutans. In addition, this oral condition is aggravated by METH users’ compulsive behavior, including the consumption of beverages with high sugar content, recurrent tooth grinding, and a lack of frequent oral hygiene. We investigated the effects of METH and sugar consumption on S. mutans biofilm formation and tooth colonization. Using a murine model of METH administration, sucrose ingestion, and oral infection, we found that the combination of METH and sucrose increases S. mutans adhesion and biofilm formation on the teeth of C57BL/6 mice. However, daily chlorhexidine-based oral rinse treatment reduces S. mutans tooth colonization. Similarly, METH has been associated with dry mouth or hyposalivation in users. Hence, we assessed the impact of human saliva on biofilm formation and demonstrated that surface preconditioning with saliva substantially reduces S. mutans biofilm formation. Our results are significant because to our knowledge, this is the first basic science study focused on elucidating the fundamentals of METH mouth using a rodent model of prolonged drug injection and S. mutans oral infection. Our findings may have important translational implications for the development of treatments for the management of METH mouth and more effective preventive public health strategies that can be applied to provide effective dental care for METH users in prisons, drug treatment centers, and health clinics.

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Metabolic Modeling of Streptococcus mutans Reveals Complex Nutrient Requirements of an Oral Pathogen

mSystems ◽

10.1128/msystems.00529-19 ◽

2019 ◽

Vol 4 (5) ◽

Cited By ~ 5

Author(s):

Kenan Jijakli ◽

Paul A. Jensen

Keyword(s):

Streptococcus Mutans ◽

Single Gene ◽

Metabolic Model ◽

The United States ◽

Defined Medium ◽

Oral Microbiome ◽

Tooth Decay ◽

Oral Pathogen ◽

Content Type ◽

A Genome

ABSTRACT Streptococcus mutans is a Gram-positive bacterium that thrives under acidic conditions and is a primary cause of tooth decay (dental caries). To better understand the metabolism of S. mutans on a systematic level, we manually constructed a genome-scale metabolic model of the S. mutans type strain UA159. The model, called iSMU, contains 675 reactions involving 429 metabolites and the products of 493 genes. We validated iSMU by comparing simulations with growth experiments in defined medium. The model simulations matched experimental results for 17 of 18 carbon source utilization assays and 47 of 49 nutrient depletion assays. We also simulated the effects of single gene deletions. The model’s predictions agreed with 78.1% and 84.4% of the gene essentiality predictions from two experimental data sets. Our manually curated model is more accurate than S. mutans models generated from automated reconstruction pipelines and more complete than other manually curated models. We used iSMU to generate hypotheses about the S. mutans metabolic network. Subsequent genetic experiments confirmed that (i) S. mutans catabolizes sorbitol via a sorbitol-6-phosphate 2-dehydrogenase (SMU_308) and (ii) the Leloir pathway is required for growth on complex carbohydrates such as raffinose. We believe the iSMU model is an important resource for understanding the metabolism of S. mutans and guiding future experiments. IMPORTANCE Tooth decay is the most prevalent chronic disease in the United States. Decay is caused by the bacterium Streptococcus mutans, an oral pathogen that ferments sugars into tooth-destroying lactic acid. We constructed a complete metabolic model of S. mutans to systematically investigate how the bacterium grows. The model provides a valuable resource for understanding and targeting S. mutans’ ability to outcompete other species in the oral microbiome.

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