Suspension of oral hygiene practices highlights key bacterial shifts in saliva, tongue, and tooth plaque during gingival inflammation and resolution.

Experimentally induced gingivitis is associated with inflammatory and microbiological changes in an otherwise healthy subject, demonstrating the impacts of discontinuing oral hygiene routines. Understanding the bacterial dynamics during the induction and resolution of gingival inflammation will aid in the development of bacterial prognostic tests and probiotics for severe oral disease. We profiled the bacterial community in 15 healthy subjects who suspended all oral-hygiene practices for three weeks.

Inter-personal diversity and temporal dynamics of dental, tongue, and salivary microbiota in the healthy oral cavity.

Oral microbes form a complex and dynamic biofilm community, which is subjected to daily host and environmental challenges. Dysbiosis of the oral biofilm is correlated with local and distal infections and postulating a baseline for the healthy core oral microbiota provides an opportunity to examine such shifts during the onset and recurrence of disease. Here we quantified the daily, weekly, and monthly variability of the oral microbiome by sequencing the largest oral microbiota time-series to date, covering multiple oral sites in ten healthy individuals.

K+ modulates genetic competence and the stress regulon of Streptococcus mutans.

Potassium (K+) is the most abundant cation in dental plaque fluid. Previously, we reported the link between K+ transport via Trk2 in Streptococcus mutans and its two critical virulence attributes: acid tolerance and surface adhesion. Herein, we build further on the intimate link between K+ levels and S.

Functional amyloids in Streptococcus mutans, their use as targets of biofilm inhibition and initial characterization of SMU_63c.

Amyloids have been identified as functional components of the extracellular matrix of bacterial biofilms. Streptococcus mutans is an established aetiologic agent of dental caries and a biofilm dweller. In addition to the previously identified amyloidogenic adhesin P1 (also known as AgI/II, PAc), we show that the naturally occurring antigen A derivative of S.

Transcriptional Profiling of the Oral Pathogen in Response to Competence Signaling Peptide XIP.

In the cariogenic , competence development is regulated by the ComRS signaling system comprised of the ComR regulator and the ComS prepeptide to the competence signaling peptide XIP (ComX-inducing peptide). Aside from competence development, XIP signaling has been demonstrated to regulate cell lysis, and recently, the expression of bacteriocins, small antimicrobial peptides used by bacteria to inhibit closely related species. Our study further explores the effect of XIP signaling on the transcriptome.

Trk2 Potassium Transport System in Streptococcus mutans and Its Role in Potassium Homeostasis, Biofilm Formation, and Stress Tolerance.

Unlabelled: Potassium (K(+)) is the most abundant cation in the fluids of dental biofilm. The biochemical and biophysical functions of K(+) and a variety of K(+) transport systems have been studied for most pathogenic bacteria but not for oral pathogens. In this study, we establish the modes of K(+) acquisition in Streptococcus mutans and the importance of K(+) homeostasis for its virulence attributes.

The copYAZ Operon Functions in Copper Efflux, Biofilm Formation, Genetic Transformation, and Stress Tolerance in Streptococcus mutans.

Unlabelled: In bacteria, copper homeostasis is closely monitored to ensure proper cellular functions while avoiding cell damage. Most Gram-positive bacteria utilize the copYABZ operon for copper homeostasis, where copA and copB encode copper-transporting P-type ATPases, whereas copY and copZ regulate the expression of the cop operon. Streptococcus mutans is a biofilm-forming oral pathogen that harbors a putative copper-transporting copYAZ operon.

In vitro manganese-dependent cross-talk between Streptococcus mutans VicK and GcrR: implications for overlapping stress response pathways.

Streptococcus mutans, a major acidogenic component of the dental plaque biofilm, has a key role in caries etiology. Previously, we demonstrated that the VicRK two-component signal transduction system modulates biofilm formation, oxidative stress and acid tolerance responses in S. mutans.

An intimate link: two-component signal transduction systems and metal transport systems in bacteria.

Bacteria have evolved various strategies to contend with high concentrations of environmental heavy metal ions for rapid, adaptive responses to maintain cell viability. Evidence gathered in the past two decades suggests that bacterial two-component signal transduction systems (TCSTSs) are intimately involved in monitoring cation accumulation, and can regulate the expression of related metabolic and virulence genes to elicit adaptive responses to changes in the concentration of these ions. Using examples garnered from recent studies, we summarize the cross-regulatory relationships between metal ions and TCSTSs.

A biochemical characterization of the DNA binding activity of the response regulator VicR from Streptococcus mutans.

Two-component systems (TCSs) are ubiquitous among bacteria and are among the most elegant and effective sensing systems in nature. They allow for efficient adaptive responses to rapidly changing environmental conditions. In this study, we investigated the biochemical characteristics of the Streptococcus mutans protein VicR, an essential response regulator that is part of the VicRK TCS.

Bacterial community composition of chronic periodontitis and novel oral sampling sites for detecting disease indicators.

Background: Periodontitis is an infectious and inflammatory disease of polymicrobial etiology that can lead to the destruction of bones and tissues that support the teeth. The management of chronic periodontitis (CP) relies heavily on elimination or at least control of known pathogenic consortia associated with the disease. Until now, microbial plaque obtained from the subgingival (SubG) sites has been the primary focus for bacterial community analysis using deep sequencing.

[Functional analysis of VicK kinase activity in Streptococcus mutans].

Objective: To investigate the regulatory function on physiology and virulence of VicK kinase activity in Streptococcus mutans.

Methods: PCR ligation mutagenesis was used to construct a vicK knock-out mutant, and kinase activity abolished VicK was expressed by a streptococcal vector in this vicK null mutant. Colony morphology, overnight culture, biofilm formation and gene expression involved in biofilm formation were analyzed.

Molecular and structural basis of glutathione import in Gram-positive bacteria via GshT and the cystine ABC importer TcyBC of Streptococcus mutans.

Glutathione (GSH) protects cells against oxidative injury and maintains a range of vital functions across all branches of life. Despite recent advances in our understanding of the transport mechanisms responsible for maintaining the spatiotemporal homeostasis of GSH and its conjugates in eukaryotes and Gram-negative bacteria, the molecular and structural basis of GSH import into Gram-positive bacteria has remained largely uncharacterized. Here, we employ genetic, biochemical and structural studies to investigate a possible glutathione import axis in Streptococcus mutans, an organism that has hitherto served as a model system.

Structural and functional analysis of the N-terminal domain of the Streptococcus gordonii adhesin Sgo0707.

The commensal Streptococcus gordonii expresses numerous surface adhesins with which it interacts with other microorganisms, host cells and salivary proteins to initiate dental plaque formation. However, this Gram-positive bacterium can also spread to non-oral sites such as the heart valves and cause infective endocarditis. One of its surface adhesins, Sgo0707, is a large protein composed of a non-repetitive N-terminal region followed by several C-terminal repeat domains and a cell wall sorting motif.

Mechanistic insights revealed by the crystal structure of a histidine kinase with signal transducer and sensor domains.

Two-component systems (TCSs) are important for the adaptation and survival of bacteria and fungi under stress conditions. A TCS is often composed of a membrane-bound sensor histidine kinase (SK) and a response regulator (RR), which are relayed through sequential phosphorylation steps. However, the mechanism for how an SK is switched on in response to environmental stimuli remains obscure.

A novel function for the competence inducing peptide, XIP, as a cell death effector of Streptococcus mutans.

In Streptococcus mutans, ComX, an alternative sigma factor, drives the transcription of the 'late-competence genes' required for genetic transformation. ComX activity is modulated by inputs from two signaling pathways, ComDE and ComRS, that respond to the competence-stimulating peptide (CSP) and the SigX-inducing peptide (XIP), respectively. In particular, the comRS, encoding the ComR regulatory protein and the ComS precursor to XIP, functions as the proximal regulatory system for ComX activation.

CinA is regulated via ComX to modulate genetic transformation and cell viability in Streptococcus mutans.

The Streptococcus mutans ComX-regulon encompasses > 200 mostly uncharacterized genes, including cinA. Here we report that cinA is regulated by ComX in the presence of the competence stimulating peptide (CSP), wherein loss of CinA (strain SmuCinA) results in reduced transformability with or without added CSP by 74- and 15-fold, respectively (P < 0.003).

TcyR regulates L-cystine uptake via the TcyABC transporter in Streptococcus mutans.

Streptococcus mutans, a primary dental pathogen, has a remarkable capacity to scavenge nutrients from the oral biofilm for its survival. Cystine is an amino acid dimer formed by the oxidation of two cysteine residues that is required for optimal growth of S. mutans, which modulates l-cystine uptake via two recently identified transporters designated TcyABC and TcyDEFGH, which have not been fully characterized.

Characterization of DNA binding sites of the ComE response regulator from Streptococcus mutans.

In Streptococcus mutans, both competence and bacteriocin production are controlled by ComC and the ComED two-component signal transduction system. Recent studies of S. mutans suggested that purified ComE binds to two 11-bp direct repeats in the nlmC-comC promoter region, where ComE activates nlmC and represses comC.

Characterization of a glutamate transporter operon, glnQHMP, in Streptococcus mutans and its role in acid tolerance.

Glutamate contributes to the acid tolerance response (ATR) of many Gram-negative and Gram-positive bacteria, but its role in the ATR of the oral bacterium Streptococcus mutans is unknown. This study describes the discovery and characterization of a glutamate transporter operon designated glnQHMP (Smu.1519 to Smu.