Journal of Oral Microbiology最新文献

Background: Non-albicans Candida species (NACs) are commonly found in carious lesions, yet their specific role in caries progression remains unclear. Hence, we conducted an in vitro study to explore how NACs interactions with Streptococcus mutans affect cariogenicity.

Materials and methods: Dual-species interkingdom biofilms were developed with S.mutans and six Candida species, C.albicans and the NACs: C.dubliniensis, C.glabrata, C.krusei, C.parapsilosis and C.tropicalis. Biofilm mass, viable cell counts, and pH were evaluated in mono- and dual-species biofilms. Quantitative RT-PCR was used to assess the expression of S.mutans genes associated with cariogenicity.

Results: Co-culturing S.mutans with either C.albicans, C.glabrata, or C.tropicalis significantly increased biofilm mass. While S.mutans numbers either increased or remained stable in dual-species biofilms, C.krusei, C.parapsilosis, and in particular C.tropicalis numbers significantly increased. All dual-species biofilms exhibited a pH below the critical demineralization level of enamel, akin to S.mutans mono-species biofilms. The expression of a battery of cariogenic genes in S.mutans was upregulated, particularly in dual-species biofilms with C.krusei and with C.tropicalis.

Conclusion: NACs influence the biofilm production and the cariogenic gene expression of S.mutans. The dual-species biofilm of S.mutans and NACs, particularly C.tropicalis, likely possess heightened cariogenic potential. Further research is warranted to unravel these intriguing interactions within interkingdom biofilms.

Background: Nitrate reductases (NR) expressed in oral bacteria reduce nitrate to nitrite. Depending on the environmental conditions and types of bacteria present nitrite can be further reduced to ammonium via Dissimilatory Nitrate Reduction to Ammonium (DNRA), or alternatively to nitric oxide (NO), which impacts cardiometabolic health.

Objective: To evaluate the associations between nitrate reduction by salivary bacteria, clinical markers of glucose metabolism, and lifestyle factors that can modulate the oral environment, potentially impacting DNRA and NR expression.

Methods: A cross-sectional study was conducted using a convenience sample of 144 participants from the San Juan Overweight Adult Longitudinal Study (SOALS), which includes data on glucose metabolism and lifestyle. DNRA and NR activities were measured in saliva under aerobic or CO₂-enriched conditions.

Results: DNRA activity was inversely associated with insulin resistance (HOMA-IR) [aerobic_{3rd vs.1st tertile}: β=-0.48 (-0.81, -0.15); CO₂-enriched_{3rd vs.1st tertile} β=-0.42 (-0.68, -0.17)], fasting blood glucose [aerobic_{3rd vs.1st tertile} β=-0.144 (-0.268, -0.019); CO₂-enriched_{3rd vs.1st tertile}: β=-0.070 (-0.130, -0.011)], and 2-h glucose [CO₂-enriched_{3rd vs.1st tertile}β=-0.21 (-0.37, -0.04)]. Current smokers had lower DNRA activity than non-smokers under aerobic conditions [β=-1.55 (-2.96, -0.14)], but higher under CO₂-enriched conditions [β = 0.93 (0.15, 1.71)]. Toothbrushing frequency (twice/day vs. once/day) was positively associated with DNRA activity under CO₂-enriched conditions [β = 4.11 (1.90, 6.32)] and with aerobic NR activity [β = 1.20, (0.14, 2.27)]. Physical activity was inversely associated with aerobic NR [β=-0.01, (-0.022, -0.003)]. Under CO₂-enriched conditions NR was inversely associated with the BMI (β=-0.11, p = 0.007). Aerobic NR was higher when sucrose was added to the assays (NADP vs. sucrose β=-0.74, p = 0.02) and positively associated with salivary nitrate levels (β = 0.002, p = 0.002).

Conclusions: Nitrate reduction by salivary bacteria is inversely associated with insulin resistance and can be modulated by lifestyle factors. This knowledge could lead to the development of novel, non-invasive approaches for monitoring and preventing diabetes progression.

Background: Effective biomarkers are urgently needed to monitor immune suppression in kidney transplantation (KT) recipients. Our study identified a close association between the salivary microbiota and immunosuppressant concentrations. It is therefore hypothesized that the salivary microbiota may be linked to immune function.

Materials and methods: We analyzed 108 saliva samples from 37 KT patients using 16S rRNA sequencing. Patients were clustered via K-means based on peripheral blood lymphocyte subset (PBLS) counts.

Results: Cluster1 exhibited significantly higher CD4⁺ T cells (p < 0.0001), CD8⁺ T cells (p < 0.0001), and B cells (p = 0.0071) versus Cluster2, with marginally NK cells (p = 0.2319). Beta diversity indicated significant differences in microbial communities. LEfSe analysis identified 34 differential taxa at the genus level. A random forest model in a fivefold three-times repeated cross-validation, developed with differential taxa, discriminated patient groups well (AUC, 75.61% ± 14.54%), with Pseudopropionibacterium most contributing. Meanwhile, only Pseudopropionibacterium correlated with more than 2 PBLSs. Cluster2 was predicted to exhibit more primary and secondary bile acid synthesis, with differential expression of related enzymes.

Conclusion: The absolute count of PBLSs is correlated with the composition of the salivary microbiota, with the strongest association observed between Pseudopropionibacterium and lymphocytes. Our study provides novel insights into immune monitoring post-KT.

Background: Glycosylation is a ubiquitous biochemical process that covalently attaches glycans to proteins or lipids, which plays a pivotal role in modulating the structure and function of these biomolecules.  This post-translational modification is prevalent in living organisms and intricately regulates various biological processes, including signaling transduction, recognition, and immune responses.  In the oral environment, bacteria ingeniously use glycosylation to enhance their adhesion to oral surfaces, which is a key step in biofilm formation and subsequent development.  This adhesion process is intimately associated with the onset and progression of oral diseases, including dental caries and periodontal disease.

Objective: This review aims to describe the types and mechanisms of glycosylation in oral bacteria, and to understand the role of glycosylation in the adhesion, biofilm formation and virulence of oral bacteria.

Methods: We reviewed articles on glycosylation in a variety of oral bacteria.

Conclusion: In cariogenic bacteria and periodontopathic pathogens, glycosylation facilitates adhesion and subsequent biofilm maturation on tooth surface.   Distinct glycosylation patterns in oral bacteria shape biofilm structure and function, influencing microbial interactions and community stability.   Pathogen-specific glycosylation signatures enhance virulence and ecological competitiveness, contributing to disease progression. Glycosylation plays a critical role in bacterial virulence and community  interactions, with significant implications for oral health and disease development.

Background: CpG oligodeoxynucleotide motifs in bacterial DNA with composition variations exhibit potent immunostimulation. The effect of different compositions in oral infections is unclear. This study aims to investigate CpG motifs in bacteria associated with endodontic diseases, periodontal diseases, and dental caries to elucidate their influence on host immune response.

Methods: Fifty oral bacterial genomes were selected for in silico analysis to determine GC% content and CpG motif frequency in each genome. The relationships between GC% content, CpG motif frequency, and genome size were assessed using correlation analysis. Normalisation of immunostimulatory sequences was implemented to enable unbiased comparison of frequency counts among bacteria.

Results: Sixty percent of bacteria exhibited medium GC% content (Mdn = 44), with no significant difference among bacteria associated with these diseases (p = 0.66). A positive correlation between GC% content and CpG motif frequency, as well as genome size and CpG motifs frequency was observed. A higher-than-mean of the human immunostimulatory motif (GTCGTT, 7/14) and the mice/rabbits immunostimulatory motif (GACGTT, 9/14) was observed in core endodontic microbiota.

Conclusion: CpG motifs in oral bacteria might drive disease progression through host immunomodulation. Variation in bacterial CpG motifs suggests targeting these motifs offers a promising therapeutic intervention.

Objective: To investigate the role of mannose phosphotransferase system (Man-PTS) EII in the alkaline resistance of Enterococcus faecalis (E. faecalis).

Methods: The Man-PTS EIID (mptD) deletion (ΔmptD) and overexpressing (+mptD) strains of E. faecalis were constructed. The contribution of the Man-PTS EII to alkaline resistance was investigated by assessing growth and biofilm formation of E. faecalis at pH 7 and 10, as well as changes in intracellular ATP levels, pH, potassium ion concentration, membrane potential and membrane permeability. The effects of mptD on the expression of other Man-PTS EII components and membrane transport-related genes were evaluated by RT-qPCR at pH 10. In addition, six clinical strains were isolated. Three strains of E. faecalis with high to low alkaline resistance were screened, and RNA sequencing was performed to further explore the role of Man-PTS EII in the alkaline resistance.

Results: mptD enhanced the alkaline resistance of E. faecalis by maintaining pH homeostasis in an alkaline environment. Overexpression of mptD induced membrane hyperpolarization, reduced membrane permeability, decreased intracellular K⁺ levels, lowered cytoplasmic pH, and elevated ATP production, while the loss of mptD reversed these effects (p < 0.05). mptD coordinated the expression of Man-PTS EII components and upregulated genes encoding membrane transporter components (p < 0.01). All Man-PTS EII components were positively related to the degree of alkaline resistance of E. faecalis (p < 0.05).

Conclusion: Man-PTS EII is a key factor in the interaction between metabolism and ion membrane transport during the alkaline resistance process of E. faecalis. This study may provide new insights for understanding the alkaline resistance of E. faecalis.

Background: Digestive system tumours (DSTs) often diagnosed late due to nonspecific symptoms. Non-invasive biomarkers are crucial for early detection and improved outcomes.

Patients and methods: We collected tongue coating samples from 710 patients diagnosed with DST and 489 healthy controls (HC) from April 2023, to December 2023. Microbial composition was analyzed using 16S rRNA sequencing, and five machine learning algorithms were applied to assess the diagnostic potential of tongue coating microbiota.

Results: Alpha diversity analysis showed that the microbial diversity in the tongue coating was significantly increased in DST patients. LEfSe analysis identified DST-enriched genera Alloprevotella and Prevotella, contrasting with HC-dominant taxa Neisseria, Haemophilus, and Porphyromonas (LDA >4). Notably, when comparing each of the four DST subtypes with the HC group, the proportion of Haemophilus in the HC group was significantly higher, and it was identified as an important feature for distinguishing the HC group. Machine learning validation demonstrated superior diagnostic performance of the Extreme Gradient Boosting (XGBoost) model, achieving an AUC of 0.926 (95% CI: 0.893-0.958) in internal validation, outperforming the other four machine learning models.

Conclusion: Tongue coating microbiota shows promise as a non-invasive biomarker for DST diagnosis, supported by robust machine learning models.

Background: Dry socket is a common post-extraction complication, characterized by the exposure of bone surfaces to the oral environment, leading to severe pain and potential infection. This study investigates the relationship between oral microbial composition and dry socket incidence in tooth extraction patients.

Methods: From 87 patients (56 normal healing, 31 dry socket), 321 microbial samples were collected at pre-, med-, and post-extraction stages from saliva and the extraction sites, and all information was documented. All samples underwent 16S rDNA sequencing and amplicon analysis.

Results: Dry socket patients exhibited distinct oral microbial diversity and composition. Prevotella, Fusobacterium, and Haemophilus strongly associated with the occurrence of dry socket. The microbial profiles in saliva revealed clearer temporal changes and healing/dry socket distinctions. The microbial network in the saliva of patients with dry socket exhibited key node/edge differences between med/post stages. Random forest analysis using pre-extraction saliva microbes to predict post-extraction symptoms, achieving a 75% accuracy rate in identifying the healthy group.

Conclusion: Haemophilus and Fusobacterium were key microbes in dry socket development and prediction. Functional changes caused by alterations in microbial composition and structure might have been the reason for the different symptoms observed after tooth extraction.

Background: Activities that control cell shape and division are critical for the survival of bacteria. However, little is known about the circuitry controlling these processes in the dental caries pathogen Streptococcus mutans.

Methodology: We designed experiments to characterize two genes, mreC and mreD, in S. mutans. Assays included cell morphology imaging, protein interaction analysis, transcriptomics, proteomics, and biofilm studies to generate a comprehensive understanding of the role of MreCD in S. mutans.

Results: Consistent with mreCD participating in cell elongation, cells lacking these genes were found to be rounder than wild-type cells. Using bacterial two-hybrid assays, interactions between MreCD and several other proteins implicated in cell elongation were observed. Further characterization, using proteomics, revealed that the surface-associated proteome is different in mutants lacking mreCD. Consistent with these changes we observed altered sucrose-mediated biofilm architecture. Loss of mreCD also had a noticeable impact on bacteriocin gene expression, which could account in part for the observation that mreCD mutants had a diminished capacity to compete with commensal streptococci.

Conclusion: Our results provide evidence that cell elongation proteins are required for normal S. mutans physiology and establish a foundation for additional examination of these and related proteins in this organism.

Background: Recent studies reported the role of Porphyromonas gingivalis (P. g) in promoting oral squamous cell carcinoma (OSCC) progression. However, the molecular mechanism remains unclear.

Materials and methods: P. g-OMVs were isolated using ultracentrifugation method and characterized by transmission electron microscopy (TEM) and nanoparticle tracking analysis (NTA). CCK-8, migration, invasion, Quantitative real-time Polymerase Chain Reaction (qRT-PCR) and immunocytochemistry assays were performed to evaluate the effect of P. g-OMVs on tumor cells' proliferation, migration, invasion, epithelial-mesenchymal transition (EMT), and ferroptosis in vitro. Western blot was performed to study the phosphorylation of transcription factor nuclear factor kappa B (NF-κB). In vivo, the effect of P. g-OMVs on the growth of OSCC was evaluated using a xenograft tumor model, followed by hematoxylin and eosin and immunohistochemistry staining.

Results: TEM and NTA demonstrated that P. g-OMVs have a vesicular structure with a particle size of around 118 nm. Compared to the control group, P. g-OMVs significantly enhance the proliferation, migration, and invasion of tumor cells. In addition, P. g-OMVs promote the EMT of OSCC cells, which can be attenuated by ferroptosis activator erastin. Moreover, P. g-OMVs inhibit feroptosis of OSCC by activating NF-κB signaling. In vivo, P. g-OMVs significantly enhance tumor growth of OSCC. Inhibition of NF-κB could significnatly reduce the growth of OSCC, which can be further rescued using ferroptosis inhibitor Ferrostain-1.

Conclusions: P. g-OMVs promote OSCC progression by modulating the ferroptosis-related EMT through NF-κB signaling.