Porphyromonas gingivalis is a keystone pathogen in periodontitis, and Streptococcus sanguinis is an abundant oral commensal bacterium associated with periodontal health. However, the interaction between P. gingivalis and S. sanguinis remains obscure. Here, we established a strategy for high-throughput measurement of the cell number of P. gingivalis in the coculture with S. sanguinis by detecting the concentration of hydrogen sulfate. The interaction between P. gingivalis and over 2000 S. sanguinis single-gene mutants was characterized using this strategy, and several interaction-associated genes in S. sanguinis were determined by detecting more P. gingivalis cells in the coculture with matched S. sanguinis mutants. Three S. sanguinis interaction-associated genes were predicted to be responsible for cysteine metabolism, and the supplementation of exogenous L-cysteine promoted the cell number of P. gingivalis in the coculture with S. sanguinis. Thus, exogenous L-cysteine and the compromised cysteine metabolism in S. sanguinis enhanced the growth of P. gingivalis in the existence of S. sanguinis. Additionally, the interaction between P. gingivalis and other Streptococcus spp. was examined, and S. pneumoniae was the only streptococci that had no inhibition on the cell number of P. gingivalis. In total, this study established a new strategy for high-throughput screening of the interaction between Streptococcus and P. gingivalis and discovered a set of genes in S. sanguinis that impacted the interaction. The influence of exogenous L-cysteine on the interaction between P. gingivalis and S. sanguinis in the oral cavity needs further investigation.

Biofilms are subjected to many environmental pressures that can influence community structure and physiology. In the oral cavity, and many other environments, biofilms are exposed to forces generated by fluid flow; however, our understanding of how oral biofilms respond to these forces remains limited. In this study, we developed a linear rocker model of fluid flow to study the impact of shear forces on Streptococcus gordonii and dental plaque-derived multispecies biofilms. We observed that as shear forces increased, S. gordonii biofilm biomass decreased. Reduced biomass was largely independent of overall bacterial growth. Transcriptome analysis of S. gordonii biofilms exposed to moderate levels of shear stress uncovered numerous genes with differential expression under shear. We also evaluated an ex vivo plaque biofilm exposed to fluid shear forces. Like S. gordonii, the plaque biofilm displayed decreased biomass as shear forces increased. Examination of plaque community composition revealed decreased diversity and compositional changes in the plaque biofilm exposed to shear. These studies help to elucidate the impact of fluid shear on oral bacteria and may be extended to other bacterial biofilm systems.

Periodontitis is caused by a dysbiosis of oral bacteria resulting in alveolar bone destruction and teeth loss. The role of platelets in pathogenesis of periodontitis is a subject of research. The release of toxins from periodontitis-associated bacteria may influence platelet function and contribute to the modulation of hemostatic or inflammatory responses. Therefore, we explored platelet function upon exposure to defined toxins: leukotoxin A from Aggregatibacter actinomycetemcomitans (LtxA), a synthetic version of the C14-Tri-LAN-Gly peptide from Fusobacterium nucleatum (C14), and lipopolysaccharides from Porphyromonas gingivalis (LPS).

The PG1037 gene is part of the uvrA-PG1037-pcrA operon in Porphyromonas gingivalis. It encodes for a protein of unknown function upregulated under hydrogen peroxide (HO)-induced oxidative stress. Bioinformatic analysis shows that PG1037 has a zinc-finger motif, two peroxidase motifs, and one cytidylate kinase domain. The aim of this study is to characterize further the role of the PG1037 recombinant protein in the unique 8-oxoG repair system in P. gingivalis.

The oral microbiome-dependent nitrate (NO )-nitrite (NO )-nitric oxide (NO) pathway may help regulate blood pressure. NO -producing bacteria in subgingival plaque are reduced in relative abundance in patients with untreated periodontitis compared with periodontally healthy patients. In periodontitis patients, the NO -producing bacteria increase several months after periodontal treatment. The early effects of periodontal treatment on NO -producing bacteria and the NO -NO -NO pathway remain unknown. The aim of this study was to determine how periodontal treatment affects the oral NO -producing microbiome and salivary NO and NO levels over time.

Type 2 diabetes mellitus (T2DM) may affect the oral microbial community, exacerbating periodontal inflammation; however, its pathogenic mechanisms remain unclear. As nucleotide-binding oligomerization domain 2 (NOD2) plays a crucial role in the activation during periodontitis (PD), it is hypothesized that changes in the oral microbial community due to diabetes enhance periodontal inflammation through the activation of NOD2.

Arg-gingipain A (RgpA) is the primary virulence factor of Porphyromonas gingivalis and contains hemagglutinin adhesin (HA), which helps bacteria adhere to cells and proteins. Hemagglutinin's functional domains include cleaved adhesin (CA), which acts as a hemagglutination and hemoglobin-binding actor. Here, we confirmed that the HA and CA genes are immunogenic, and using adjuvant chemokine to target dendritic cells (DCs) enhanced protective autoimmunity against P. gingivalis-induced periodontal disease.

Fusobacterium nucleatum, a gram-negative anaerobic bacterium abundantly found in the human oral cavity, is widely recognized as a key pathobiont responsible for the initiation and progression of periodontal diseases due to its remarkable aggregative capabilities. Numerous clinical studies have linked F. nucleatum with unfavorable prognostic outcomes in various malignancies. In further research, scholars have partially elucidated the mechanisms underlying F. nucleatum's impact on various types of cancer, thus gaining a certain comprehension of the role played by F. nucleatum in cancer. In this comprehensive review, we present an in-depth synthesis of the interplay between F. nucleatum and different cancers, focusing on aspects such as tumor initiation, metastasis, chemoresistance, and modulation of the tumor immune microenvironment and immunotherapy. The implications for cancer diagnosis and treatment are also summarized. The objective of this review is to enhance our comprehension of the intricate relationship between F. nucleatum and oncogenic pathogenesis, while emphasizing potential therapeutic strategies.

To examine the characteristics of the salivary microbiome in Type 2 diabetes mellitus (T2DM) patients with or without periodontitis.

Filifactor alocis is a newly appreciated member of the periodontal community with a strong periodontal disease correlation. Little is known about the survival mechanisms by which F. alocis copes with oxidative stress and establishes the infection within the local inflammatory microenvironment of the periodontal pocket. The aim of this study is to investigate if F. alocis putative peroxiredoxin/AhpC protein FA768 may constitute an alkyl hydroperoxide reductase system utilizing putative thioredoxin reductase protein FA608, and putative thioredoxin/glutaredoxin homolog FA1411/FA455.

This study aimed to characterize the taxonomic composition of intraradicular multispecies biofilms (IMBs) formed in situ in a model to reproduce clinical conditions. Twelve palatal roots of maxillary molars had its canals prepared. Two roots were randomly selected to sterility control. Ten intraoral prosthetic appliances with lateral slots were fabricated. The roots were positioned in the slots with the canal access open to the oral cavity. Eight volunteers wore the appliance for 21 days, and two wore it at two different time points. One root from each appliance was removed and stored at -20°C until DNA extraction and sequencing (n = 10). Biofilm was analyzed using next-generation sequencing and bioinformatics. The V4 hyper-variable region of the 16SrRNA gene was amplified and sequenced. For data analyses, the mothur pipeline was used for 16SrRNA processing, and subsequent analyses of the sequence dataset were performed in R using the MicrobiomeAnalyst R package. The taxonomy-based analysis of bacterial communities identified 562 operational taxonomic units (OTUs), which belonged to 93 genera, 44 families, and 8 phyla. Bacterial colonization was different for each biofilm, and samples did not have the same group of bacteria. Alpha and beta diversity analysis revealed some general patterns of sample clustering. A core microbiome of prevalent OTUs and genera was identified. IMBs were heterogeneous when analyzed individually, but some diversity patterns were found after sample clustering. The experimental model seemed to reproduce the actual biofilm composition in endodontic infections, which suggests that it may be used to evaluate disinfection protocols.

Infection is a known cause of abdominal aortic aneurysm (AAA), and matrix metalloproteases-2 (MMP-2) secreted by vascular smooth muscle cells (SMCs) plays a key role in the structural disruption of the middle layer of the arteries during AAA progression. The periodontal pathogen Porphyromonas gingivalis is highly associated with the progression of periodontitis. GroEL protein of periodontal pathogens is an important virulence factor that can invade the body through either the bloodstream or digestive tract and is associated with numerous systemic diseases. Although P. gingivalis aggravates AAA by increasing the expression of MMP-2 in animal studies, the molecular mechanism through which P. gingivalis regulates the expression of MMP-2 is still unknown and requires further investigation. In this study, we first confirmed through animal experiments that P. gingivalis GroEL promotes MMP-2 secretion from vascular SMCs, thereby aggravating Ang II-induced aortic remodeling and AAA formation. In addition, rat vascular SMCs and A7r5 cells were used to investigate the underlying mechanisms in vitro. The results demonstrated that GroEL can promote the interaction between the K639 site of MMP-2 and SUMO-1, leading to MMP-2 SUMOylation, which inhibits the reoccurrence of non-K639-mediated monoubiquitylation. Hence, the monoubiquitylation-mediated lysosomal degradation of MMP-2 is inhibited, consequently promoting MMP-2 stability and production. SUMOylation may facilitate intra-endoplasmic reticulum (ER) and Golgi trafficking of MMP-2, thereby enhancing its transport capacity. In conclusion, this is the first report demonstrating the presence of a novel posttranslational modification, SUMOylation, in the MMP family, suggesting that P. gingivalis GroEL may exacerbate AAA formation by increasing MMP-2 production through SUMOylation in vascular SMCs. This study also provides a novel perspective on the role of SUMOylation in MMP-2-induced systemic diseases.

The oral cavity harbors a diverse and dynamic bacterial biofilm community which is pivotal to oral health maintenance and, if turning dysbiotic, can contribute to various diseases. Glycans as unsurpassed carriers of biological information are participating in underlying processes that shape oral health and disease. Bacterial glycoinfrastructure-encompassing compounds as diverse as glycoproteins, lipopolysaccharides (LPSs), cell wall glycopolymers, and exopolysaccharides-is well known to influence bacterial fitness, with direct effects on bacterial physiology, immunogenicity, lifestyle, and interaction and colonization capabilities. Thus, understanding oral bacterias' glycoinfrastructure and encoded glycolanguage is key to elucidating their pathogenicity mechanisms and developing targeted strategies for therapeutic intervention. Driven by their known immunological role, most research in oral glycobiology has been directed onto LPSs, whereas, recently, glycoproteins have been gaining increased interest. This review draws a multifaceted picture of the glycolanguage, with a focus on glycoproteins, manifested in prominent oral bacteria, such as streptococci, Porphyromonas gingivalis, Tannerella forsythia, and Fusobacterium nucleatum. We first define the characteristics of the different glycoconjugate classes and then summarize the current status of knowledge of the structural diversity of glycoconjugates produced by oral bacteria, describe governing biosynthetic pathways, and list biological roles of these energetically costly compounds. Additionally, we highlight emerging research on the unraveling impact of oral glycoinfrastructure on dental caries, periodontitis, and systemic conditions. By integrating current knowledge and identifying knowledge gaps, this review underscores the importance of studying the glycolanguage oral bacteria speak to advance our understanding of oral microbiology and develop novel antimicrobials.

Considered the second largest and most diverse microbiome after the gut, the human oral ecosystem is complex with diverse and niche-specific microorganisms. Although evidence is growing for the importance of oral microbiome in supporting a healthy immune system and preventing local and systemic infections, the influence of craniomaxillofacial (CMF) trauma and routine reconstructive surgical treatments on community structure and function of oral resident microbes remains unknown. CMF injuries affect a large number of people, needing extensive rehabilitation with lasting morbidity and loss of human productivity. Treatment efficacy can be complicated by the overgrowth of opportunistic commensals or multidrug-resistant pathogens in the oral ecosystem due to weakened host immune function and reduced colonization resistance in a dysbiotic oral microbiome.

Oral lichen planus (OLP) is one of the most common oral mucosal diseases, exhibiting a higher prevalence in women than men, but its pathogenesis is still unclear. Current research suggests that microbial dysbiosis may play an important role in the pathogenesis of OLP. Our previous research has found that the increase of Prevotella melaninogenica and decrease of Streptococcus salivarius have been identified as a potential pathogenic factor in OLP. Consequently, the objective of this study is to examine whether S. salivarius can counteract the detrimental effects of P. melaninogenica on the integrity of the epithelial barrier function.

This study aimed to characterize the taxonomic composition of intraradicular multispecies biofilms (IMB) formed in situ in a model to reproduce clinical conditions. Twelve palatal roots of maxillary molars had its canals prepared. Two roots were randomly selected to sterility control. Ten intraoral prosthetic appliances with lateral slots were fabricated. The roots were positioned in the slots with the canal access open to the oral cavity. Eight volunteers wore the appliance for 21 days, and two wore it at two different time points. One root from each appliance was removed and stored at -20°C until DNA extraction and sequencing (n = 10). Biofilm was analyzed using next-generation sequencing and bioinformatics. The V4 hyper-variable region of the 16SrRNA gene was amplified and sequenced. For data analyses, the mothur pipeline was used for 16SrRNA processing, and subsequent analyses of the sequence dataset were performed in R using the Microbiome Analyst R package. The taxonomy-based analysis of bacterial communities identified 562 operational taxonomic units (OTUs), which belonged to 93 genera, 44 families, and 8 phyla. Bacterial colonization was different for each biofilm, and samples did not have the same group of bacteria. Alpha and beta diversity analysis revealed some general patterns of sample clustering. A core microbiome of prevalent OTUs and genera was identified. IMBs were heterogeneous when analyzed individually, but some diversity patterns were found after sample clustering. The experimental model seemed to reproduce the actual biofilm composition in endodontic infections, which suggests that it may be used to evaluate disinfection protocols.

Numerous Treponema species are prevalent in the dysbiotic subgingival microbial community during periodontitis. The major outer sheath protein is a highly expressed virulence factor of the well-characterized species Treponema denticola. Msp forms an oligomeric membrane protein complex with adhesin and porin properties and contributes to host-microbial interaction. Treponema maltophilum and Treponema lecithinolyticum species are also prominent during periodontitis but are relatively understudied. Msp-like membrane surface proteins exist in T. maltophilum (MspA) and T. lecithinolyticum (MspTL), but limited information exists regarding their structural features or functionality. Protein profiling reveals numerous differences between these species, but minimal differences between strains of the same species. Using protein modeling tools, we predict MspA and MspTL monomeric forms to be large β-barrel structures composed of 20 all-next-neighbor antiparallel β strands which most likely adopt a homotrimer formation. Using cell fractionation, Triton X-114 phase partitioning, heat modifiability, and chemical and detergent release assays, we found evidence of amphiphilic integral membrane-associated oligomerization for both native MspA and MspTL in intact spirochetes. Proteinase K accessibility and immunofluorescence assays demonstrate surface exposure of MspA and MspTL. Functionally, purified recombinant MspA or MspTL monomer proteins can impair neutrophil chemotaxis. Expressions of MspA or MspTL with a PelB leader sequence in Escherichia coli also demonstrate surface exposure and can impair neutrophil chemotaxis in an in vivo air pouch model of inflammation. Collectively, our data demonstrate that MspA and MspTL membrane proteins can contribute to pathogenesis of these understudied oral spirochete species.

Clustered regularly interspaced short palindromic repeats (CRISPRs) are DNA sequences capable of editing a host genome sequence. CRISPR and its specific CRISPR-associated (Cas) protein complexes have been adapted for various applications. These include activating or inhibiting specific genetic sequences or acting as molecular scissors to cut and modify the host DNA precisely. CRISPR-Cas systems are also naturally present in many oral bacteria, where they aid in nutrition, biofilm formation, inter- and intraspecies communication (quorum sensing), horizontal gene transfer, virulence, inflammation modulation, coinfection, and immune response evasion. It even functions as an adaptive immune system, defending microbes against invading viruses and foreign genetic elements from other bacteria by targeting and degrading their DNA. Recently, CRISPR-Cas systems have been tested as molecular editing tools to manipulate specific genes linked with periodontal disease (such as periodontitis) and as novel methods of delivering antimicrobial agents to overcome antimicrobial resistance. With the rapidly increasing role of CRISPR in treating inflammatory diseases, its application in periodontal disease is also becoming popular. Therefore, this review aims to discuss the different types of CRISPR-Cas in oral microbes and their role in periodontal disease pathogenesis and precision periodontal therapy.

Metronidazole (MTZ) is an antimicrobial agent used to treat anaerobic infections. It has been hypothesized that MTZ may also have anti-inflammatory properties, but the evidence is limited and has not been previously reviewed. Thus, this scoping review aimed to answer the following question: "What is the evidence supporting anti-inflammatory properties of metronidazole that are not mediated by its antimicrobial effects?"