Dancing with the Stars: How Choreographed Bacterial Interactions Dictate Nososymbiocity and Give Rise to Keystone Pathogens, Accessory Pathogens, and Pathobionts

Deciphering the pathogenic risks of microplastics as emerging particulate organic matter in aquatic ecosystem

Microplastics are accumulating rapidly in aquatic ecosystems, providing habitats for pathogens and vectors for antibiotic resistance genes (ARGs), potentially increasing pathogenic risks. However, few studies have considered microplastics as particulate organic matter (POM) to elucidate their pathogenic risks and underlying mechanisms. Here, we performed microcosm experiments with microplastics and natural POM (leaves, algae, soil), thoroughly investigating their distinct effects on the community compositions, functional profiles, opportunistic pathogens, and ARGs in Particle-Associated (PA) and Free-Living (FL) bacterial communities. We found that both microplastics and leaves have comparable impacts on microbial community structures and functions, enriching opportunistic pathogens and ARGs, which may pose potential environmental risks. These effects are likely driven by their influences on water properties, including dissolved organic carbon, nitrate, DO, and pH. However, microplastics uniquely promoted pathogens as keystone species and further amplified their capacity as hosts for ARGs, potentially posing a higher pathogenic risk than natural POM. Our research also emphasized the importance of considering both PA and FL bacteria when assessing microplastic impacts, as they exhibited different responses. Overall, our study elucidates the role and underlying mechanism of microplastics as an emerging POM in intensifying pathogenic risks of aquatic ecosystems in comparison with conventional natural POM.

Curcumin inhibits growth of Porphyromonas gingivalis by arrest of bacterial dipeptidyl peptidase activity

Background

Curcumin is a multi-functional polyphenol with anti-bacterial and anti-inflammatory effects and may have potential for treatment of periodontal diseases. The present study was conducted to examine the molecular basis of the anti-bacterial effect of curcumin against Porphyromonas gingivalis using metabolome analysis.

Materials and Methods

P. gingivalis were incubated with 10 µg/mL curcumin, and then metabolites were analyzed with CE-TOF/MS. Expression levels of sigma factors were also evaluated using RT-PCR assays. The activities of dipeptidyl peptidases (DPPs) were assessed by examining the degradation reactions of MCA-labeled peptides.

Results

The relative amounts of various glycogenic amino acids were significantly decreased when P. gingivalis was incubated with curcumin. Furthermore, the metabolites on the amino acid degradation pathway, including high-energy compounds such as ATP, various intermediate metabolites of RNA/DNA synthesis, nucleoside sugars and amino sugars were also decreased. Additionally, the expression levels of sigma-54 and sigma-70 were significantly decreased, and the same results as noted following nutrient starvation. Curcumin also significantly suppressed the activities of some DPPs, while the human DPP-4 inhibitors markedly inhibited the growth of P. gingivalis and activities of the DPPs.

Conclusions

Curcumin suppresses the growth of P. gingivalis by inhibiting DPPs and also interferes with nucleic acid synthesis and central metabolic pathways, beginning with amino acid metabolism.

Identification of keystone taxa in root canals and periapical lesions of post-treatment endodontic infections: Next generation microbiome research

AIM

The aim of this study was to analyse and compare the microbiome present in root canals and periapical lesions of teeth with post-treatment infections, and to identify the presence of keystone taxa in both habitats using next-generation sequencing analysis.

METHODOLOGY

Apices and periapical lesions of patients with post-treatment apical periodontitis were surgically extracted. Specimens were cryo-pulverized, bacterial DNA was extracted, and the V3-V4 hypervariable regions of the 16S rRNA gene were sequenced using the Illumina Miseq platform. Bioinformatic analysis was carried out with Mothur software, whilst diversity indices were obtained using operational taxonomic units (OTUs). The diversity indices were compared with the Kruskal-Wallis test, and community composition differences were explored with Permutational Multivariate Analysis of Variance (PERMANOVA). A bacterial functional study was performed with the Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) analysis. Co-occurrence network analyses were performed using the Sparse Correlations for Compositional data (SparCC). Eigencentrality, clr-based abundance and ubiquitousness were applied to infer keystone taxa. P values <.05 were considered statistically significant.

RESULTS

Thirty-two apices and thirty-nine periapical lesions were sequenced and analysed. A similar alpha-diversity (p < .05) and community composition (p = .91) was observed for apices and lesion samples. The most abundant OTUs identified amongst all samples included Fusobacterium nucleatum, Prevotella loescheii, Streptococcus intermedius, Porphyromonas gingivalis, Parvimonas micra, Synergistetes bacterium, Tannerella forsythia and Peptostreptococcus stomatis. The metabolic pathways with >0.81% abundances included membrane transport, genetic information processing and metabolic pathways. F. nucleatum was identified as a keystone taxon as it showed ubiquitousness, an eigenvector centrality value of 0.83 and a clr-based abundance >4.

CONCLUSIONS

The microbiome in apices and periapical lesions of post-treatment endodontic infections showed a similar diversity and taxonomic composition. Co-occurrence network analyses at OTU level identified F. nucleatum as a keystone taxon candidate in these infections.

The root canal microbiome diversity and function. A whole-metagenome shotgun analysis

AIM

To evaluate the root canal microbiome composition and bacterial functional capability in cases of primary and secondary apical periodontitis utilizing whole-metagenome shotgun sequencing.

METHODOLOGY

Twenty-two samples from patients with primary root canal infections, and 18 samples obtained from previously treated teeth currently diagnosed with apical periodontitis were analysed with whole-metagenome shotgun sequencing at a depth of 20 M reads. Taxonomic and functional gene annotations were made using MetaPhlAn3 and HUMAnN3 software. The Shannon and Chao1 indices were utilized to measure alpha diversity. Differences in community composition were evaluated utilizing analysis of similarity (ANOSIM) using Bray-Curtis dissimilarities. The Wilcoxon rank sum test was used to compare differences in taxa and functional genes.

RESULTS

Microbial community variations within a community were significantly lower in secondary relative to primary infections (alpha diversity p = .001). Community composition was significantly different in primary versus secondary infection (R = .11, p = .005). The predominant taxa observed among samples (>2.5%) were Pseudopropionibacterium propionicum, Prevotella oris, Eubacterium infirmum, Tannerella forsythia, Atopobium rimae, Peptostreptococcus stomatis, Bacteroidetes bacterium oral taxon 272, Parvimonas micra, Olsenella profusa, Streptococcus anginosus, Lactobacillus rhamnosus, Porphyromonas endodontalis, Pseudoramibacter alactolyticus, Fusobacterium nucleatum, Eubacterium brachy and Solobacterium moorei. The Wilcoxon rank test revealed no significant differences in relative abundances of functional genes in both groups. Genes with greater relative abundances (top 25) were associated with genetic, signalling and cellular processes including the iron and peptide/nickel transport system. Numerous genes encoding toxins were identified: exfoliative toxin, haemolysins, thiol-activated cytolysin, phospholipase C, cAMP factor, sialidase, and hyaluronic glucosaminidase.

CONCLUSIONS

Despite taxonomic differences between primary and secondary apical periodontitis, the functional capability of the microbiomes was similar.

Microbial diagnostics in periodontal diseases

Microbial analytical methods have been instrumental in elucidating the complex microbial etiology of periodontal diseases, by shaping our understanding of subgingival community dynamics. Certain pathobionts can orchestrate the establishment of dysbiotic communities that can subvert the host immune system, triggering inflammation and tissue destruction. Yet, diagnosis and management of periodontal conditions still rely on clinical and radiographic examinations, overlooking the well-established microbial etiology. This review summarizes the chronological emergence of periodontal etiological models and the co-evolution with technological advances in microbial detection. We additionally review the microbial analytical approaches currently accessible to clinicians, highlighting their value in broadening the periodontal assessment. The epidemiological importance of obtaining culture-based antimicrobial susceptibility profiles of periodontal taxa for antibiotic resistance surveillance is also underscored, together with clinically relevant analytical approaches to guide antibiotherapy choices, when necessary. Furthermore, the importance of 16S-based community and shotgun metagenomic profiling is discussed in outlining dysbiotic microbial signatures. Because dysbiosis precedes periodontal damage, biomarker identification offers early diagnostic possibilities to forestall disease relapses during maintenance. Altogether, this review highlights the underutilized potential of clinical microbiology in periodontology, spotlighting the clinical areas most conductive to its diagnostic implementation for enhancing prevention, treatment predictability, and addressing global antibiotic resistance.

Microbial- and host immune cell-derived extracellular vesicles in the pathogenesis and therapy of periodontitis: A narrative review

Periodontitis is a chronic inflammatory disease caused by dysbiotic biofilms and destructive host immune responses. Extracellular vesicles (EVs) are circulating nanoparticles released by microbes and host cells involved in cell-to-cell communication, found in body biofluids, such as saliva and gingival crevicular fluid (GCF). EVs are mainly involved in cell-to-cell communication, and may hold promise for diagnostic and therapeutic purposes. Periodontal research has examined the potential involvement of bacterial- and host-cell-derived EVs in disease pathogenesis, diagnosis, and therapy, but data remains scarce on immune cell- or microbial-derived EVs. In this narrative review, we first provide an overview of the role of microbial and host-derived EVs on disease pathogenesis. Recent studies reveal that Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans-derived outer membrane vesicles (OMVs) can activate inflammatory cytokine release in host cells, while M1 macrophage EVs may contribute to bone loss. Additionally, we summarised current in vitro and pre-clinical research on the utilisation of immune cell and microbial-derived EVs as potential therapeutic tools in the context of periodontal treatment. Studies indicate that EVs from M2 macrophages and dendritic cells promote bone regeneration in animal models. While bacterial EVs remain underexplored for periodontal therapy, preliminary research suggests that P. gingivalis OMVs hold promise as vaccine candidates. Finally, we acknowledge the current limitations present in the field of translating immune cell derived EVs and microbial derived EVs in periodontology. It is concluded that microbial and host immune cell-derived EVs have a role in periodontitis pathogenesis and hence may be useful for studying disease pathophysiology, and as diagnostic and treatment monitoring biomarkers.

The polymicrobial pathogenicity of Porphyromonas gingivalis

Accumulating microbiome data and mechanistic studies in vitro and in vivo have refined our understanding of the oral microbiota as a functionally integrated polymicrobial community. Emergent properties of these communities are driven to a large extent by interspecies communication which can be based on physical association, secreted small molecules or nutritional exchange. Porphyromonas gingivalis is a consensus periodontal pathogen; however, virulence is only expressed in the context of a polymicrobial community. Multivalent fimbriae mediate attachment to other oral species which can initiate a distinct transcriptional program in both constituents of the binding pair. P. gingivalis also responds to small molecules and nutritional cues produced by partner organisms. Physiological interdependence forms the basis of complex networks of cooperating organisms which begin to resemble an organismal entity exhibiting a spectrum of pathogenic potential.

Potential diagnostic markers and therapeutic targets for periodontitis and Alzheimer's disease based on bioinformatics analysis

BACKGROUND AND OBJECTIVE

As a chronic inflammatory disease, periodontitis threatens oral health and is a risk factor for Alzheimer's disease (AD). There is growing evidence that these two diseases are closely related. However, current research is still incomplete in understanding the common genes and common mechanisms between periodontitis and AD. In this study, we aimed to identify common genes in periodontitis and AD and analyze the relationship between crucial genes and immune cells to provide new therapeutic targets for clinical treatment.

MATERIALS AND METHODS

We evaluated differentially expressed genes (DEGs) specific to periodontitis and AD. Co-expressed genes were identified by obtaining gene expression profile data from the Gene Expression Omnibus (GEO) database. Using the STRING database, protein-protein interaction (PPI) networks were constructed, and essential genes were identified. We also used four algorithms to identify critical genes and constructed regulatory networks. The association of crucial genes with immune cells and potential therapeutic effects was also assessed.

RESULTS

PDGFRB, VCAN, TIMP1, CHL1, EFEMP2, and IGFBP5 were obtained as crucial common genes. Immune infiltration analysis showed that Natural killer cells and Myeloid-derived suppressor cells were significantly differentially expressed in patients with PD and AD compared with the normal group. FOXC1 and GATA2 are important TFs for PD and AD. MiR-23a, miR-23b, miR-23a, and miR-23b were associated with AD and PD. Finally, the hub genes retrieved from the DSigDB database indicate multiple drug molecule and drug-target interactions.

CONCLUSION

This study reveals commonalities in common hub genes and immune infiltration between periodontitis and AD, and the analysis of six hub genes and immune cells may provide new insights into potential therapeutic directions for the pathogenesis of periodontitis complicated by AD.

Phyllosphere bacterial community dynamics in response to bacterial wildfire disease: succession and interaction patterns

Plants interact with complex microbial communities in which microorganisms play different roles in plant development and health. While certain microorganisms may cause disease, others promote nutrient uptake and resistance to stresses through a variety of mechanisms. Developing plant protection measures requires a deeper comprehension of the factors that influence multitrophic interactions and the organization of phyllospheric communities. High-throughput sequencing was used in this work to investigate the effects of climate variables and bacterial wildfire disease on the bacterial community's composition and assembly in the phyllosphere of tobacco (Nicotiana tabacum L.). The samples from June (M1), July (M2), August (M3), and September (M4) formed statistically separate clusters. The assembly of the whole bacterial population was mostly influenced by stochastic processes. PICRUSt2 predictions revealed genes enriched in the M3, a period when the plant wildfire disease index reached climax, were associated with the development of the wildfire disease (secretion of virulence factor), the enhanced metabolic capacity and environmental adaption. The M3 and M4 microbial communities have more intricate molecular ecological networks (MENs), bursting with interconnections within a densely networked bacterial population. The relative abundances of plant-beneficial and antagonistic microbes Clostridiales, Bacillales, Lactobacillales, and Sphingobacteriales, showed significant decrease in severally diseased sample (M3) compared to the pre-diseased samples (M1/M2). Following the results of MENs, we further test if the correlating bacterial pairs within the MEN have the possibility to share functional genes and we have unraveled 139 entries of such horizontal gene transfer (HGT) events, highlighting the significance of HGT in shaping the adaptive traits of plant-associated bacteria across the MENs, particularly in relation to host colonization and pathogenicity.

Oral streptococci: modulators of health and disease

Streptococci are primary colonizers of the oral cavity where they are ubiquitously present and an integral part of the commensal oral biofilm microflora. The role oral streptococci play in the interaction with the host is ambivalent. On the one hand, they function as gatekeepers of homeostasis and are a prerequisite for the maintenance of oral health - they shape the oral microbiota, modulate the immune system to enable bacterial survival, and antagonize pathogenic species. On the other hand, also recognized pathogens, such as oral Streptococcus mutans and Streptococcus sobrinus, which trigger the onset of dental caries belong to the genus Streptococcus. In the context of periodontitis, oral streptococci as excellent initial biofilm formers have an accessory function, enabling late biofilm colonizers to inhabit gingival pockets and cause disease. The pathogenic potential of oral streptococci fully unfolds when their dissemination into the bloodstream occurs; streptococcal infection can cause extra-oral diseases, such as infective endocarditis and hemorrhagic stroke. In this review, the taxonomic diversity of oral streptococci, their role and prevalence in the oral cavity and their contribution to oral health and disease will be discussed, focusing on the virulence factors these species employ for interactions at the host interface.

Interspecies metabolite transfer fuels the methionine metabolism of Fusobacterium nucleatum to stimulate volatile methyl mercaptan production

The major oral odor compound methyl mercaptan (CH3SH) is strongly associated with halitosis and periodontitis. CH3SH production stems from the metabolism of polymicrobial communities in periodontal pockets and on the tongue dorsum. However, understanding of CH3SH-producing oral bacteria and their interactions is limited. This study aimed to investigate CH3SH production by major oral bacteria and the impact of interspecies interactions on its generation. Using a newly constructed large-volume anaerobic noncontact coculture system, Fusobacterium nucleatum was found to be a potent producer of CH3SH, with that production stimulated by metabolic interactions with Streptococcus gordonii, an early dental plaque colonizer. Furthermore, analysis of extracellular amino acids using an S. gordonii arginine-ornithine antiporter (ArcD) mutant demonstrated that ornithine excreted from S. gordonii is a key contributor to increased CH3SH production by F. nucleatum. Further study with 13C, 15N-methionine, as well as gene expression analysis, revealed that ornithine secreted by S. gordonii increased the demand for methionine through accelerated polyamine synthesis by F. nucleatum, leading to elevated methionine pathway activity and CH3SH production. Collectively, these findings suggest that interaction between S. gordonii and F. nucleatum plays a key role in CH3SH production, providing a new insight into the mechanism of CH3SH generation in oral microbial communities. A better understanding of the underlying interactions among oral bacteria involved in CH3SH generation can lead to the development of more appropriate prophylactic approaches to treat halitosis and periodontitis. An intervention approach like selectively disrupting this interspecies network could also offer a powerful therapeutic strategy.IMPORTANCEHalitosis can have a significant impact on the social life of affected individuals. Among oral odor compounds, CH3SH has a low olfactory threshold and halitosis is a result of its production. Recently, there has been a growing interest in the collective properties of oral polymicrobial communities, regarded as important for the development of oral diseases, which are shaped by physical and metabolic interactions among community participants. However, it has yet to be investigated whether interspecies interactions have an impact on the production of volatile compounds, leading to the development of halitosis. The present findings provide mechanistic insights indicating that ornithine, a metabolite excreted by Streptococcus gordonii, promotes polyamine synthesis by Fusobacterium nucleatum, resulting in a compensatory increase in demand for methionine, which results in elevated methionine pathway activity and CH3SH production. Elucidation of the mechanisms related to CH3SH production is expected to lead to the development of new strategies for managing halitosis.

Metagenomic analysis of healthy and diseased peri-implant microbiome under different periodontal conditions: a cross-sectional study

BACKGROUND

Peri-implantitis is a polybacterial infection that can lead to the failure of dental implant rehabilitation. This study aimed to profile the microbiome of the peri-implant plaque and estimate the effect of periodontitis on it among 40 Chinese participants with dental implant prostheses and presenting with varying peri-implant and periodontal health states.

METHODS

Submucosal plaque samples were collected from four distinct clinical categories based on both their implant and periodontal health status at sampling point. Clinical examinations of dental implant and remaining teeth were carried out. Metagenomic analysis was then performed.

RESULTS

The microbiome of the peri-implantitis sites differed from that of healthy implant sites, both taxonomically and functionally. Moreover, the predominant species in peri-implantitis sites were slightly affected by the presence of periodontitis. T. forsythia, P. gingivalis, T. denticola, and P. endodontalis were consistently associated with peri-implantitis and inflammatory clinical parameters regardless of the presence of periodontitis. Prevotella spp. and P. endodontalis showed significant differences in the peri-implantitis cohorts under different periodontal conditions. The most distinguishing function between diseased and healthy implants is related to flagellar assembly, which plays an important role in epithelial cell invasion.

CONCLUSIONS

The composition of the peri-implant microbiome varied in the diseased and healthy states of implants and is affected by individual periodontal conditions. Based on their correlations with clinical parameters, certain species are associated with disease and healthy implants. Flagellar assembly may play a vital role in the process of peri-implantitis.

Synthesis of novel metal silica nanoparticles exhibiting antimicrobial potential and applications to combat periodontitis

Periodontitis is a severe form of gum disease caused by bacterial plaque that affects millions of people and has substantial worldwide health and economic implications. However, current clinical antiseptic and antimicrobial drug therapies are insufficient because they frequently have numerous side effects and contribute to widespread bacterial resistance. Recently, nanotechnology has shown promise in the synthesis of novel periodontal therapeutic materials. Nanoparticles are quickly replacing antibiotics in the treatment of bacterial infections, and their potential application in dentistry is immense. The alarming increases in antimicrobial resistance further emphasize the importance of exploring and utilizing nanotechnology in the fight against tooth diseases particularly periodontitis. We developed 16 different combinations of mesoporous silica nanomaterials in this study by ageing, drying, and calcining them with 11 different metals including silver, zinc, copper, gold, palladium, ruthenium, platinum, nickel, cerium, aluminium, and zirconium. The antibacterial properties of metal-doped silica were evaluated using four distinct susceptibility tests. The agar well diffusion antibacterial activity test, which measured the susceptibility of the microbes being tested, as well as the antibacterial efficacy of mesoporous silica with different silica/metal ratios, were among these studies. The growth kinetics experiment was used to investigate the efficacy of various metal-doped silica nanoparticles on microbial growth. To detect growth inhibitory effects, the colony-forming unit assay was used. Finally, MIC and MBC tests were performed to observe the inhibition of microbial biofilm formation. Our findings show that silver- and zinc-doped silica nanoparticles synthesized using the sol-gel method can be effective antimicrobial agents against periodontitis-causing microbes. This study represents the pioneering work reporting the antimicrobial properties of metal-loaded TUD-1 mesoporous silica, which could be useful in the fight against other infectious diseases too.

Upper gastrointestinal tract microbiota with oral origin in relation to oesophageal squamous cell carcinoma

Introduction: Poor oral hygiene is linked to high risks of many systemic diseases, including cancers. Oral dysbiosis is closely associated with poor oral hygiene, causing tooth loss, gingivitis, and periodontitis. We provide a summary of studies and discuss the risk factors for oesophageal squamous cell carcinoma (ESCC) from a microbial perspective in this review.Methods: A literature search of studies published before December 31, 2022 from PubMed, Web of Science, and The Cochrane Library was performed. The search strategies included the following keywords: (1) oral care, oral health, oral hygiene, dental health, dental hygiene, tooth loss, teeth loss, tooth absence, missing teeth, edentulism, tooth brushing, mouthwash, and tooth cleaning; (2) esophageal, esophagus, oesophagus, and oesophageal; (3) cancer, carcinoma, tumor, and neoplasm.Discussion: Poor oral health, indicated by infrequent tooth brushing, chronic periodontitis, and tooth loss, has been associated with an increased risk of squamous dysplasia and ESCC. Oral microbial diversity and composition are profoundly dysregulated during oesophageal tumorigenesis. Similar to the oral microbiota, the oesophageal microbiota varies distinctly in multiple bacterial taxa in ESCC and gastric cardia adenocarcinoma, both of which have high co-occurrence rates in the "Oesophageal Cancer Belt". In addition, the potential roles of oncogenic viruses in ESCC have also been discussed. We also briefly explore the potential mechanisms underlying the tumor-promoting role of dysregulated microbiota for the development of therapeutic targeting strategies.Conclusion: Poor oral health is an established risk indicator of ESCC. The dysbiosis of microbiota in upper gastrointestinal tract that highly resembles the oral microbial ecosystem but with distinct features at individual sites contributes to the development and progression of ESCC.

Macrophage-related gingival transcriptomic patterns and microbiome alterations in experimental periodontitis in nonhuman primates

OBJECTIVE

This study examined the microbiome features specifically related to host macrophage polarization in health, initiation and progression of periodontitis, and in resolution samples using a nonhuman primate model of ligature-induced periodontitis.

BACKGROUND

The oral microbiome is a complex of bacterial phyla, genera, and species acquired early in life into the individual autochthonous oral ecology. The microbiome changes overtime in response to both intrinsic and extrinsic stressors, and transitions to a dysbiotic ecology at sites of periodontal lesions.

METHODS

Comparisons were made between the microbial and host features in young (≤7 years) and adult (≥12 years) cohorts of animals. Footprints of macrophage-related genes in the gingival tissues were evaluated using expression profiles including M0, M1, and M2 related genes.

RESULTS

Within the gingival tissues, similar macrophage-related gene patterns were observed with significant increases with disease initiation and continued elevation throughout disease in both age groups. Approximately, 70% of the taxa were similar in relative abundance between the two groups; however, the adults showed a large number of OTUs that were significantly altered compared with the younger animals. Developing a correlation map identified three major node levels of interactions that comprised approximately ⅓ of the Operational Taxonomic Units (OTUs) that dominated the microbiomes across the samples. Also noted was a much greater frequency of significant correlations of individual OTUs with the macrophage phenotype markers, compared with disease and resolution samples in both age groups, with a greater frequency in the younger group. Moreover, these correlations were assigned to differentially expressed genes representing M0, M1, and M2-related phenotypes. A cluster analyses across the macrophage-related transcriptome and the OTUs demonstrated multiple somewhat distinct bacterial consortia, incorporating both commensal and putative pathogens, linked to the gene responses that differed in health, disease, and resolution samples. Finally, there were minimal alterations in the OTUs in individual clusters with specific macrophage-related responses in the younger group, while in the adult samples substantial variations were noted with genes from all macrophage phenotypes.

CONCLUSIONS

The results confirmed important features that could reflect macrophage polarization in periodontal lesions, and provided some initial data supporting specific members of the oral microbiome feature prominently related to specific gene response patterns consistent with macrophages in the gingival tissues.

Chronological analysis of periodontal bone loss in experimental periodontitis in mice

OBJECTIVES

Periodontal disease is understood to be a result of dysbiotic interactions between the host and the biofilm, causing a unique reaction for each individual, which in turn characterizes their susceptibility. The objective of this study was to chronologically evaluate periodontal tissue destruction induced by systemic bacterial challenge in known susceptible (BALB/c) and resistant (C57BL/6) mouse lineages.

MATERIAL AND METHODS

Animals, 6-8 weeks old, were allocated into three experimental groups: Negative control (C), Gavage with sterile carboxymethyl cellulose 2%-without bacteria (Sham), and Gavage with carboxymethyl cellulose 2% + Porphyromonas gingivalis (Pg-W83). Before infection, all animals received antibiotic treatment (sulfamethoxazole/trimethoprim, 400/80 mg/5 mL) for 7 days, followed by 3 days of rest. Microbial challenge was performed 3 times per week for 1, 2, or 3 weeks. After that, the animals were kept until the completion of 42 days of experiments, when they were euthanized. The alveolar bone microarchitecture was assessed by computed microtomography.

RESULTS

Both C57BL/6 and BALB/c mice exhibited significant bone volume loss and lower trabecular thickness as well as greater bone porosity compared to the (C) and (Sham) groups after 1 week of microbial challenge (p < .001). When comparing only the gavage groups regarding disease implantation, time and lineage, it was possible to observe that within 1 week of induction the disease was more established in BALB/c than in C57BL/6 (p < .05).

CONCLUSIONS

Our results reflected that after 1 week of microbial challenge, there was evidence of alveolar bone loss for both lineages, with the loss observed in BALB/c mice being more pronounced.

Immunological link between periodontitis and type 2 diabetes deciphered by single-cell RNA analysis

BACKGROUND

Type 2 diabetes mellitus (DM) is a complex metabolic disorder that causes various complications, including periodontitis (PD). Although a bidirectional relationship has been reported between DM and PD, their immunological relationship remains poorly understood. Therefore, this study aimed to compare the immune response in patients with PD alone and in those with both PD and DM (PDDM) to expand our knowledge of the complicated connection between PD and DM.

METHODS

Peripheral blood mononuclear cells were collected from 11 healthy controls, 10 patients with PD without DM, and six patients with PDDM, followed by analysis using single-cell RNA sequencing. The differences among groups were then compared based on intracellular and intercellular perspectives.

RESULTS

Compared to the healthy state, classical monocytes exhibited the highest degree of transcriptional change, with elevated levels of pro-inflammatory cytokines in both PD and PDDM. DM diminished the effector function of CD8+ T and natural killer (NK) cells as well as completely modified the differentiation direction of these cells. Interestingly, a prominent pathway, RESISTIN, which is known to increase insulin resistance and susceptibility to diabetes, was found to be activated under both PD and PDDM conditions. In particular, CAP1+ classical monocytes from patients with PD and PDDM showed elevated nuclear factor kappa B-inducing kinase activity.

CONCLUSIONS

Overall, this study elucidates how the presence of DM contributes to the deterioration of T/NK cell immunity and the immunological basis connecting PD to DM.

Ageing and Inflammation: What Happens in Periodontium?

Periodontitis is a chronic inflammatory disease with a high incidence and severity in the elderly population, making it a significant public health concern. Ageing is a primary risk factor for the development of periodontitis, exacerbating alveolar bone loss and leading to tooth loss in the geriatric population. Despite extensive research, the precise molecular mechanisms underlying the relationship between ageing and periodontitis remain elusive. Understanding the intricate mechanisms that connect ageing and inflammation may help reveal new therapeutic targets and provide valuable options to tackle the challenges encountered by the rapidly expanding global ageing population. In this review, we highlight the latest scientific breakthroughs in the pathways by which inflammaging mediates the decline in periodontal function and triggers the onset of periodontitis. We also provide a comprehensive overview of the latest findings and discuss potential avenues for future research in this critical area of investigation.

Molecular commensalism-how to investigate underappreciated health-associated polymicrobial communities

The study of human commensal bacteria began with the first observation of prokaryotes >340 years ago. Since then, the study of human-associated microbes has been justifiably biased toward the study of infectious pathogens. However, the role of commensal microbes has in recent years begun to be understood with some appreciation of them as potential protectors of host health rather than bystanders. As our understanding of these valuable microbes grows, it highlights how much more remains to be learned about them and their roles in maintaining health. We note here that a thorough framework for the study of commensals, both in vivo and in vitro is overall lacking compared to well-developed methodologies for pathogens. The modification and application of methods for the study of pathogens can work well for the study of commensals but is not alone sufficient to properly characterize their relationships. This is because commensals live in homeostasis with the host and within complex communities. One difficulty is determining which commensals have a quantifiable impact on community structure and stability as well as host health, vs benign microbes that may indeed serve only as bystanders. Human microbiomes are composed of bacteria, archaea, fungi, and viruses. This review focuses particularly on oral bacteria, yet many of the principles of commensal impacts on host health observed in the mouth can translate well to other host sites. Here, we discuss the value of commensals, the shortcomings involved in model systems for their study, and some of the more notable impacts they have upon not only each other but host health.

Deconstructing taxa x taxa xenvironment interactions in the microbiota: A theoretical examination

A major objective of microbial ecology is to identify how the composition of microbial taxa shapes host phenotypes. However, most studies focus on pairwise interactions and ignore the potentially significant effects of higher-order microbial interactions.Here, we quantify the effects of higher-order interactions among taxa on host infection risk. We apply our approach to an in silico dataset that is built to resemble a population of insect hosts with gut-associated microbial communities at risk of infection from an intestinal parasite across a breadth of nutrient environmental contexts.We find that the effect of higher-order interactions is considerable and can change appreciably across environmental contexts. Furthermore, we show that higher-order interactions can stabilize community structure thereby reducing host susceptibility to parasite invasion.Our approach illustrates how incorporating the effects of higher-order interactions among gut microbiota across environments can be essential for understanding their effects on host phenotypes.

Preliminary analysis of mucosal and salivary bacterial communities in oral lichen planus

OBJECTIVE

To characterize the bacterial community from different oral niches (buccal mucosa and saliva) in oral lichen planus (OLP) patients.

SUBJECTS AND METHODS

This preliminary study analyzed site-specific (mucosa and saliva) microbial landscape of 20 OLP patients and 10 healthy controls.

RESULTS

The microbial diversity was similar between OLP patients and healthy controls in both salivary and mucosal communities. However, the topological properties of co-occurrence networks of salivary and mucosal microbiome were different between healthy controls and OLP patients. SparCC analysis inferred three and five keystone taxa in the salivary and mucosal microbial networks of healthy controls, respectively. However, in the salivary and mucosal bacterial networks of OLP patients, only one hub OTU and three OTUs were identified as keystone taxa, respectively. In addition, analysis of community cohesion revealed that mucosal microbial community in OLP patients had lower stability than that in healthy controls. In final, correlation assay showed that the clinical severity of OLP was positively associated with the relative abundance of Rothia in saliva but negatively associated with that of Porphyromonas on mucosa.

CONCLUSIONS

The salivary and mucosal bacterial communities of OLP patients differ in terms of composition, the genera associated with OLP severity, and co-occurrence patterns.

Inflammatory macrophages exploited by oral streptococcus increase IL-1B release via NLRP6 inflammasome

Chronic inflammatory periodontal disease develops in part from the infiltration of a large number of classically activated inflammatory macrophages that release inflammatory cytokines important for disease progression, including inflammasome-dependent interleukin (IL)-1β. Streptococcus gordonii is a normally commensal oral microorganism; while not causative, recent evidence indicates that commensal oral microbes are required for the full development of periodontal disease. We have recently reported that inflammatory macrophages counterintuitively allow for the increased survival of phagocytosed S. gordonii over nonactivated or alternatively activated macrophages. This survival is dependent on increased reactive oxygen species production within the phagosome of the inflammatory macrophages, and resistance by the bacterium and can result in S. gordonii damaging the phagolysosomes. Here, we show that activated macrophages infected with live S. gordonii release more IL-1β than non-activated macrophages infected with either live or dead S. gordonii, and that the survival of oral Streptococci are more dependent on macrophage activation than other Gram positive microbes, both classical pathogens and commensals. We also find that S. gordonii-dependent inflammatory macrophage inflammasome activation requires the cytoplasmic NLRP6. Overall, our results suggest S. gordonii is capable of evading immune destruction, increasing inflammatory mediators, and increasing inflammatory macrophage response, and that this ability is increased under conditions of inflammation. This work reveals additional mechanisms by which normally commensal oral streptococci-macrophage interactions can change, resulting in increased release of mature IL-1β, potentially contributing to an environment that perpetuates inflammation.

Social networking at the microbiome-host interface

Microbial species colonizing host ecosystems in health or disease rarely do so alone. Organisms conglomerate into dynamic heterotypic communities or biofilms in which interspecies and interkingdom interactions drive functional specialization of constituent species and shape community properties, including nososymbiocity or pathogenic potential. Cell-to-cell binding, exchange of signaling molecules, and nutritional codependencies can all contribute to the emergent properties of these communities. Spatial constraints defined by community architecture also determine overall community function. Multilayered interactions thus occur between individual pairs of organisms, and the relative impact can be determined by contextual cues. Host responses to heterotypic communities and impact on host surfaces are also driven by the collective action of the community. Additionally, the range of interspecies interactions can be extended by bacteria utilizing host cells or host diet to indirectly or directly influence the properties of other organisms and the community microenvironment. In contexts where communities transition to a dysbiotic state, their quasi-organismal nature imparts adaptability to nutritional availability and facilitates resistance to immune effectors and, moreover, exploits inflammatory and acidic microenvironments for their persistence.

Oral microbiome associated with differential ratios of Porphyromonas gingivalis and Streptococcus cristatus

Background

Periodontitis has been recently defined as a dysbiotic disease resulting from imbalanced oral microbiota. The transition of microbial communities from commensal to periodontitis-associated ones likely requires colonization by specific pathogens, including Porphyromonas gingivalis. We previously reported an antagonistic relationship between Streptococcus cristatus and P. gingivalis and the role of S. cristatus in inhibition of the biofilm formation, invasion, and gingipain enzymatic activity of P. gingivalis. Given the importance of P. gingivalis as a keystone pathogen of polymicrobial communities, the determinants of P. gingivalis levels, its interaction with the core microbiota, and association with the pathogenic potential of the microbial communities need to be addressed.

Results

This present study intends to determine the role of S. cristatus in altering interactions of P. gingivalis with other oral bacteria in a complex context. We collected dental plaque samples from periodontitis patients and assigned them into two groups based on their ratios of S. cristatus and P. gingivalis. We then characterized microbial profiles of the dental plaque samples using shotgun metagenomic sequencing and subsequently compared oral microbial composition and functional capabilities between groups with high or low S. cristatus-P. gingivalis ratios. Taxonomic annotation showed significant differences in microbial compositions at both genus and species levels between the two groups. Notably, a higher microbial composition diversity was observed in the samples with low S. cristatus-P. gingivalis ratios. The antibiotic resistance gene profiles of the two groups are also distinct, with significantly increased diversity and abundance of antibiotic resistance genes in the dental plaque samples with low S. cristatus-P. gingivalis ratios, which likely lead to elevated virulence potential.

Conclusions

Overall, our work highlights the importance of S. cristatus-P. gingivalis ratios in influencing the virulence of the oral microbiome. Approaches to enhance S. cristatus-P. gingivalis ratios in oral microbial communities will be attractive for revising the dysbiotic oral microbiome.

Comparison of microbiological profile of enterotoxigenic Bacteroides fragilis (ETBF) isolates from subjects with colorectal cancer (CRC) or intestinal pre-cancerous lesions versus healthy individuals and evaluation of environmental factors involved in intestinal dysbiosis

OBJECTIVE

The aim of this study was to analyze enterotoxigenic Bacteroides fragilis (ETBF) isolates from colorectal biopsies of subjects with a histological analysis positive for colorectal cancer (CRC), pre-cancerous lesions (pre-CRC) or with a healthy intestinal tissue and to evaluate the environmental factors that may not only concur to CRC development but may also affect gut microbiota composition.

METHODS

ETBF isolates were typed using the ERIC-PCR method, while PCR assays were performed to investigate the bft alleles, the B. fragilis pathogenicity island (BFPAI) region and the cepA, cfiA and cfxA genes. Susceptibility to antibiotics was tested using the agar dilution method. Environmental factors that could play a role in promoting intestinal dysbiosis were evaluated throughout a questionnaire administered to the subjects enrolled.

RESULTS

Six different ERIC-PCR types were identified. The type denominated C in this study was the most prevalent, in particular among the biopsies of subjects with pre-CRC, while an isolate belonging to a different type, denominated F, was detected in a biopsy from a subject with CRC. All the ETBF isolates from pre-CRC or CRC subjects had a B. fragilis pathogenicity island (BFPAI) region pattern I, while those from healthy individuals showed also different patterns. Furthermore, 71% of isolates from subjects with pre-CRC or CRC were resistant to two or more classes of antibiotics vs 43% of isolates from healthy individuals. The B. fragilis toxin BFT1 was the most frequently detected in this study, confirming the constant circulation of this isoform strains in Italy. Interestingly, BFT1 was found in 86% of the ETBF isolates from patients with CRC or pre-CRC, while the BFT2 was prevalent among the ETBF isolates from healthy subjects. No substantial differences based on sex, age, tobacco and alcohol consumption were observed between healthy and non-healthy individuals included in this study, while most of the subjects with CRC or pre-CRC lesions were subjected to pharmacological therapy (71%) and showed a body mass index (BMI) that falls within the overweight range (86%).

CONCLUSIONS

Our data suggest that some types of ETBF seem to better adapt and colonize the human gut and that the selective pressure exerted by factors related to lifestyle, such as pharmacological therapy and weight, could facilitate their persistence in the gut and their possible involvement in CRC development.

Phylogenomic analysis of the Porphyromonas gingivalis - Porphyromonas gulae duo: approaches to the origin of periodontitis

Porphyromonas gingivalis is an oral human pathogen associated with the onset and progression of periodontitis, a chronic immune-inflammatory disease characterized by the destruction of the teeth-supporting tissue. P. gingivalis belongs to the genus Porphyromonas, which is characterized by being composed of Gram-negative, asaccharolytic, non-spore-forming, non-motile, obligatory anaerobic species, inhabiting niches such as the oral cavity, urogenital tract, gastrointestinal tract and infected wound from different mammals including humans. Among the Porphyromonas genus, P. gingivalis stands out for its specificity in colonizing the human oral cavity and its keystone pathogen role in periodontitis pathogenesis. To understand the evolutionary process behind P. gingivalis in the context of the Pophyoromonas genus, in this study, we performed a comparative genomics study with publicly available Porphyromonas genomes, focused on four main objectives: (A) to confirm the phylogenetic position of P. gingivalis in the Porphyromonas genus by phylogenomic analysis; (B) the definition and comparison of the pangenomes of P. gingivalis and its relative P. gulae; and (C) the evaluation of the gene family gain/loss events during the divergence of P. gingivalis and P. gulae; (D) the evaluation of the evolutionary pressure (represented by the calculation of Tajima-D values and dN/dS ratios) comparing gene families of P. gingivalis and P. gulae. Our analysis found 84 high-quality assemblies representing P. gingivalis and 14 P. gulae strains (from a total of 233 Porphyromonas genomes). Phylogenomic analysis confirmed that P. gingivalis and P. gulae are highly related lineages, close to P. loveana. Both organisms harbored open pangenomes, with a strong core-to-accessory ratio for housekeeping genes and a negative ratio for unknown function genes. Our analyses also characterized the gene set differentiating P. gulae from P. gingivalis, mainly associated with unknown functions. Relevant virulence factors, such as the FimA, Mfa1, and the hemagglutinins, are conserved in P. gulae, P. gingivalis, and P. loveana, suggesting that the origin of those factors occurred previous to the P. gulae - P. gingivalis divergence. These results suggest an unexpected evolutionary relationship between the P. gulae - P. gingivalis duo and P. loveana, showing more clues about the origin of the role of those organisms in periodontitis.

Impact of Polymicrobial Infection on Fitness of Streptococcus gordonii In Vivo

Pathogenic microbial ecosystems are often polymicrobial, and interbacterial interactions drive emergent properties of these communities. In the oral cavity, Streptococcus gordonii is a foundational species in the development of plaque biofilms, which can contribute to periodontal disease and, after gaining access to the bloodstream, target remote sites such as heart valves. Here, we used a transposon sequencing (Tn-Seq) library of S. gordonii to identify genes that influence fitness in a murine abscess model, both as a monoinfection and as a coinfection with an oral partner species, Porphyromonas gingivalis. In the context of a monoinfection, conditionally essential genes were widely distributed among functional pathways. Coinfection with P. gingivalis almost completely changed the nature of in vivo gene essentiality. Community-dependent essential (CoDE) genes under the coinfection condition were primarily related to DNA replication, transcription, and translation, indicating that robust growth and replication are required to survive with P. gingivalis in vivo. Interestingly, a group of genes in an operon encoding streptococcal receptor polysaccharide (RPS) were associated with decreased fitness of S. gordonii in a coinfection with P. gingivalis. Individual deletion of two of these genes (SGO_2020 and SGO_2024) resulted in the loss of RPS production by S. gordonii and increased susceptibility to killing by neutrophils. P. gingivalis protected the RPS mutants by inhibiting neutrophil recruitment, degranulation, and neutrophil extracellular trap (NET) formation. These results provide insight into genes and functions that are important for S. gordonii survival in vivo and the nature of polymicrobial synergy with P. gingivalis. Furthermore, we show that RPS-mediated immune protection in S. gordonii is dispensable and detrimental in the presence of a synergistic partner species that can interfere with neutrophil killing mechanisms. IMPORTANCE Bacteria responsible for diseases originating at oral mucosal membranes assemble into polymicrobial communities. However, we know little regarding the fitness determinants of the organisms that initiate community formation. Here, we show that the extracellular polysaccharide of Streptococcus gordonii, while important for streptococcal survival as a monoinfection, is detrimental to survival in the context of a coinfection with Porphyromonas gingivalis. We found that the presence of P. gingivalis compensates for immune protective functions of extracellular polysaccharide, rendering production unnecessary. The results show that fitness determinants of bacteria in communities differ substantially from those of individual species in isolation. Furthermore, constituents of communities can undertake activities that relieve the burden of energetically costly biosynthetic reactions on partner species.

The Treatment of Severe Periodontitis Using a Local Antiseptic Desiccant and Subgingival Mechanical Instrumentation: A Pilot Study

This randomized, split-mouth, controlled clinical study assessed the additional clinical benefits of a local desiccant antimicrobial agent (HY) combined with subgingival mechanical instrumentation (SRP) vs. SRP alone in treating severe periodontitis. Patients with stages III and IV periodontitis received full-mouth periodontal examinations at baseline and after a three-month follow-up. Two randomly selected hemiarches in each periodontitis patient were treated with SRP plus HY and were included in the test group, while the other two hemiarches received only SRP and were included in the control group. In thirty patients, the analyses of the evolution of the periodontal parameters over time showed statistically significant mean differences for the probing depths and clinical attachment level values resulting from all the examined sites, as well as from the interproximal sites (p < 0.001) in both the test and control groups. The intergroup comparisons of the same four parameters showed no significant differences (p = 0.322, p = 0.36, p = 0.516, and p = 0.509, respectively). Based on these study results, no additional benefits were obtained after HY subgingival applications.

Characteristics of the Salivary Microbiota in Periodontal Diseases and Potential Roles of Individual Bacterial Species To Predict the Severity of Periodontal Disease

The purposes of this study were to examine the compositional changes in the salivary microbiota according to the severity of periodontal disease and to verify whether the distribution of specific bacterial species in saliva can distinguish the severity of disease. Saliva samples were collected from 8 periodontally healthy controls, 16 patients with gingivitis, 19 patients with moderate periodontitis, and 29 patients with severe periodontitis. The V3 and V4 regions of the 16S rRNA gene in the samples were sequenced, and the levels of 9 bacterial species showing significant differences among the groups by sequencing analysis were identified using quantitative real-time PCR (qPCR). The predictive performance of each bacterial species in distinguishing the severity of disease was evaluated using a receiver operating characteristic curve. Twenty-nine species, including Porphyromonas gingivalis, increased as the severity of disease increased, whereas 6 species, including Rothia denticola, decreased. The relative abundances of P. gingivalis, Tannerella forsythia, Filifactor alocis, and Prevotella intermedia determined by qPCR were significantly different among the groups. The three bacterial species P. gingivalis, T. forsythia, and F. alocis were positively correlated with the sum of the full-mouth probing depth and were moderately accurate at distinguishing the severity of periodontal disease. In conclusion, the salivary microbiota showed gradual compositional changes according to the severity of periodontitis, and the levels of P. gingivalis, T. forsythia, and F. alocis in mouth rinse saliva had the ability to distinguish the severity of periodontal disease. IMPORTANCE Periodontal disease is one of the most widespread medical conditions and the leading cause of tooth loss, imposing high economic costs and an increasing burden worldwide as life expectancy increases. Changes in the subgingival bacterial community during the progression of periodontal disease can affect the entire oral ecosystem, and bacteria in saliva can reflect the degree of bacterial imbalance in the oral cavity. This study explored whether the specific bacterial species in saliva can distinguish the severity of periodontal disease by analyzing the salivary microbiota and suggested P. gingivalis, T. forsythia, and F. alocis as biomarkers for distinguishing the severity of periodontal disease in saliva.

Viral Co-Infections and Antiviral Immunity in Honey Bees

Over the past few decades, honey bees have been facing an increasing number of stressors. Beyond individual stress factors, the synergies between them have been identified as a key factor in the observed increase in colony mortality. However, these interactions are numerous and complex and call for further research. Here, in line with our need for a systemic understanding of the threats that they pose to bee health, we review the interactions between honey bee viruses. As viruses are obligate parasites, the interactions between them not only depend on the viruses themselves but also on the immune responses of honey bees. Thus, we first summarise our current knowledge of the antiviral immunity of honey bees. We then review the interactions between specific pathogenic viruses and their interactions with their host. Finally, we draw hypotheses from the current literature and suggest directions for future research.

Selenomonas sputigena acts as a pathobiont mediating spatial structure and biofilm virulence in early childhood caries

Streptococcus mutans has been implicated as the primary pathogen in childhood caries (tooth decay). While the role of polymicrobial communities is appreciated, it remains unclear whether other microorganisms are active contributors or interact with pathogens. Here, we integrate multi-omics of supragingival biofilm (dental plaque) from 416 preschool-age children (208 males and 208 females) in a discovery-validation pipeline to identify disease-relevant inter-species interactions. Sixteen taxa associate with childhood caries in metagenomics-metatranscriptomics analyses. Using multiscale/computational imaging and virulence assays, we examine biofilm formation dynamics, spatial arrangement, and metabolic activity of Selenomonas sputigena, Prevotella salivae and Leptotrichia wadei, either individually or with S. mutans. We show that S. sputigena, a flagellated anaerobe with previously unknown role in supragingival biofilm, becomes trapped in streptococcal exoglucans, loses motility but actively proliferates to build a honeycomb-like multicellular-superstructure encapsulating S. mutans, enhancing acidogenesis. Rodent model experiments reveal an unrecognized ability of S. sputigena to colonize supragingival tooth surfaces. While incapable of causing caries on its own, when co-infected with S. mutans, S. sputigena causes extensive tooth enamel lesions and exacerbates disease severity in vivo. In summary, we discover a pathobiont cooperating with a known pathogen to build a unique spatial structure and heighten biofilm virulence in a prevalent human disease.

Illuminating the oral microbiome and its host interactions: animal models of disease

Periodontitis and caries are driven by complex interactions between the oral microbiome and host factors, i.e. inflammation and dietary sugars, respectively. Animal models have been instrumental in our mechanistic understanding of these oral diseases, although no single model can faithfully reproduce all aspects of a given human disease. This review discusses evidence that the utility of an animal model lies in its capacity to address a specific hypothesis and, therefore, different aspects of a disease can be investigated using distinct and complementary models. As in vitro systems cannot replicate the complexity of in vivo host-microbe interactions and human research is typically correlative, model organisms-their limitations notwithstanding-remain essential in proving causality, identifying therapeutic targets, and evaluating the safety and efficacy of novel treatments. To achieve broader and deeper insights into oral disease pathogenesis, animal model-derived findings can be synthesized with data from in vitro and clinical research. In the absence of better mechanistic alternatives, dismissal of animal models on fidelity issues would impede further progress to understand and treat oral disease.

Alteration of oral bacteriome of smokeless tobacco users and their association with oral cancer

Smokeless tobacco (SLT) is certainly one of the major risk factors associated with oral cancer. Disruption of oral microbiota-host homeostasis contributes to the progression of oral cancer. Here, we profiled SLT users' oral bacterial composition and inferred their functions by sequencing 16S rDNA V₃-V₄ region and PICRUSt2, respectively. Oral bacteriome of SLT users (with or without oral premalignant lesions), SLT with alcohol co-users, and non-SLT consumers were compared. Oral bacteriome is shaped primarily by SLT use and the incidence of oral premalignant lesions (OPL). A significantly increased bacterial α-diversity was monitored in SLT users with OPL compared to in SLT users without OPL and non-users, whereas β-diversity was significantly explained by OPL status. Overrepresented genera were Prevotella, Fusobacterium, Veillonella, Haemophilus, Capnocytophaga, and Leptotrichia in SLT users having OPL. LEfSe analysis identified 16 genera as a biomarker that were differentially abundant in SLT users having OPL. The functional prediction of genes significantly increased for several metabolic pathways, more importantly, were nitrogen metabolism, nucleotide metabolism, energy metabolism, and biosynthesis/biodegradation of secondary metabolites in SLT users having OPL. Furthermore, HPV-16 and EBV, but not HPV-18, were considerably connected with the SLT users having OPL. Overall, this study provides evidence that SLT utilization and OPL development are associated with oral bacteriome dysbiosis indicating the enrichment of bacterial species known for their contribution to oral carcinogenesis. Therefore, delineating the cancer-inducing bacterial population in SLT users will facilitate the future development of microbiome-targeted therapies. KEY POINTS: • SLT consumption significantly elevates oral bacterial diversity. • Prevalent significant genera are Prevotella, Veillonella, and Haemophilus in SLT users with OPL. • SLT promotes the occurrence of the cancer-inducing bacterial population.

Oral polymicrobial communities: Assembly, function, and impact on diseases

Oral microbial communities assemble into complex spatial structures. The sophisticated physical and chemical signaling systems underlying the community enable their collective functional regulation as well as the ability to adapt by integrating environmental information. The combined output of community action, as shaped by both intra-community interactions and host and environmental variables, dictates homeostatic balance or dysbiotic disease such as periodontitis and dental caries. Oral polymicrobial dysbiosis also exerts systemic effects that adversely affect comorbidities, in part due to ectopic colonization of oral pathobionts in extra-oral tissues. Here, we review new and emerging concepts that explain the collective functional properties of oral polymicrobial communities and how these impact health and disease both locally and systemically.

Retrospective analysis of Porphyromonas gingivalis in patients with nasopharyngeal carcinoma in central China

Little is known about the presence and possible role of Porphyromonas gingivalis (P. gingivalis) in nasopharyngeal carcinoma (NPC), its co-infection with Epstein-Barr virus (EBV), or their association with clinical characteristics of patients with NPC in Central China, where NPC is non-endemic. A total of 45 NPC formalin-fixed paraffin-embedded (FFPE) tissues were retrospectively analyzed using immunohistochemistry (IHC) and a nested PCR combined with DNA sequencing to detect the presence of P. gingivalis, and using reverse transcription-quantitative PCR to detect the presence of EBV. Clinical data including EBV and P. gingivalis status were associated with overall survival (OS). All tumors were undifferentiated, non-keratinizing carcinomas, of which 40/45 (88.9%) were positive for EBV (EBV⁺), 26/45 (57.8%) were positive for P. gingivalis (by IHC), and 7/45 (15.6%) were positive for P. gingivalis DNA (P. gingivalis ⁺). All seven P. gingivalis DNA-positive NPCs were co-infected with EBV. The 5-year survival rates of the patients with EBV^-/P. gingivalis ^-, EBV⁺/P. gingivalis ^-, and EBV⁺/P. gingivalis ⁺ tumors were 60.0% (3/5), 39.4% (13/33) and 42.9% (3/7), respectively. No significant difference was found between the OS of NPC patients among the different infection groups (P=0.793). In conclusion, to the best of our knowledge, this is the first study to describe and confirm the presence of P. gingivalis in FFPE tissues from patients with NPC. P. gingivalis was found to co-exist with EBV in NPC tumor tissues, but is not etiologically relevant to NPC in non-endemic areas, such as Central China.

A Local Desiccant Antimicrobial Agent as an Alternative to Adjunctive Antibiotics in the Treatment of Periodontitis: A Narrative Review

Periodontitis is one of the most common oral polymicrobial infectious diseases induced by the complex interplay between the altered subgingival microbiota and the host’s dysregulated immune-inflammatory response, leading to the initiation of progressive and irreversible destruction of the periodontal tissues and eventually to tooth loss. The main goal of cause-related periodontal therapy is to eliminate the dysbiotic subgingival biofilm in order to arrest local inflammation and further periodontal tissue breakdown. Because, in some cases, subgingival mechanical instrumentation has limited efficiency in achieving those goals, various adjunctive therapies, mainly systemic and locally delivered antimicrobials, have been proposed to augment its effectiveness. However, most adjunctive antimicrobials carry side effects; therefore, their administration should be precociously considered. HybenX® (HY) is a commercial therapeutical agent with decontamination properties, which has been studied for its effects in treating various oral pathological conditions, including periodontitis. This review covers the current evidence regarding the treatment outcomes and limitations of conventional periodontal therapies and provides information based on the available experimental and clinical studies related to the HY mechanism of action and effects following its use associated with subgingival instrumentation and other types of dental treatments.

Structural equation modelling the impact of antimicrobials on the human microbiome. Colonization resistance versus colonization susceptibility as case studies

The impact of antimicrobials on the human microbiome and its relationship to human health are of great interest. How antimicrobial exposure might drive change within specific constituents of the microbiome to effect clinically relevant endpoints is difficult to study. Clinical investigation of each step within a network of causation would be challenging if done 'step-by-step'. An analytic tool of great potential to clinical microbiome research is structural equation modelling (SEM), which has a long history of applications to research questions arising within subject areas as diverse as psychology and econometrics. SEM enables postulated models based on a network of causation to be tested en bloc by confrontation with data derived from the literature. Case studies for the potential application of SEM techniques are colonization resistance (CR) and its counterpart, colonization susceptibility (CS), wherein specific microbes within the microbiome are postulated to either impede (CR) or facilitate (CS) invasive infection with pathogenic bacteria. These postulated networks have three causation steps: exposure to specific antimicrobials are key drivers, clinically relevant infection endpoints are the measurable observables and the activity of key microbiome constituents mediating CR or CS, which may be unobservable, appear as latent variables in the model. SEM methods have potential application towards evaluating the activity of specific antimicrobial agents within postulated networks of causation using clinically derived data.

The multifaceted virulence of adherent-invasive Escherichia coli

The surge in inflammatory bowel diseases, like Crohn's disease (CD), is alarming. While the role of the gut microbiome in CD development is unresolved, the frequent isolation of adherent-invasive Escherichia coli (AIEC) strains from patient biopsies, together with their propensity to trigger gut inflammation, underpin the potential role of these bacteria as disease modifiers. In this review, we explore the spectrum of AIEC pathogenesis, including their metabolic versatility in the gut. We describe how AIEC strains hijack the host defense mechanisms to evade immune attrition and promote inflammation. Furthermore, we highlight the key traits that differentiate AIEC from commensal E. coli. Deciphering the main components of AIEC virulence is cardinal to the discovery of the next generation of antimicrobials that can selectively eradicate CD-associated bacteria.

Gain a Baby Lose a Tooth-Is There an Association between Periodontitis and Preterm Birth?

Preterm birth serves as one of the leading causes of neonatal mortality worldwide. The underlying mechanisms that contribute to preterm birth are not yet fully understood. However, an association between periodontitis and preterm birth has been proposed. The periodontal status and presence of periodontal pathogens in women with different birth outcomes have been previously examined. However, varying definitions of periodontitis and different microbiological methods make their interpretation challenging. The aim of this case-control study on women with and without preterm birth was to investigate their periodontal status using the current classification system for periodontal diseases. Moreover, differences in the periodontal microbiome of the study participants were investigated. Therefore, we collected data on oral and periodontal parameters in 77 puerperal women divided into two groups based on gestational age at delivery: 33 patients with preterm birth (PTB, <37 weeks) and 44 patients with term birth (TB, >37 weeks). These data included pocket probing depth (PPD), clinical attachment loss (CAL), bleeding on probing (BOP), gingival-bleeding index, DMFT index, and gynecologic and dental history. In addition, their oral microbiome was explored. Median CAL and percentage PPD ≥ 4 mm were significantly higher in the PTB group than in the TB group (p = 0.0128 and p = 0.047, respectively). Birth weight was significantly higher in periodontally healthy women than in those with gingivitis (p = 0.0078) or periodontitis (p = 0.0127). The periodontal microbiome differed significantly between groups. Our results are underlining the possible association between periodontitis and preterm delivery. Women with periodontitis had babies with significantly lower birth weights. The microbiome varied between the groups.

Oral biofilm dysbiosis during experimental periodontitis

OBJECTIVES

We have previously characterized the main osteoimmunological events that occur during ligature periodontitis. This study aims to determine the polymicrobial community shifts that occur during disease development.

METHODS

Periodontitis was induced in C57BL/6 mice using the ligature-induced periodontitis model. Healthy oral mucosa swabs and ligatures were collected every 3 days from 0 to 18 days post-ligature placement. Biofilm samples were evaluated by 16SrRNA gene sequencing (Illumina MiSeq) and QIIME. Time-course changes were determined by relative abundance, diversity, and rank analyses (PERMANOVA, Bonferroni-adjusted).

RESULTS

Microbial differences between health and periodontal inflammation were observed at all phylogenic levels. An evident microbial community shift occurred in 25 genera during the advancement of "gingivitis" (3-6 days) to periodontitis (9-18 days). From day 0 to 18, dramatic changes were identified in Streptococcus levels, with an overall decrease (54.04%-0.02%) as well an overall increase of Enterococcus and Lactobacillus (23.7%-73.1% and 10.1%-70.2%, respectively). Alpha-diversity decreased to its lowest at 3 days, followed by an increase in diversity as disease advancement. Beta-diversity increased after ligature placement, indicating that bone loss develops in response to a greater microbial variability (p = 0.001). Levels of facultative and strict anaerobic bacteria augmented over the course of disease progression, with a total of eight species significantly different during the 18-day period.

CONCLUSION

The data supports that murine gingival inflammation and alveolar bone loss develop in response to microbiome shifts. Bacterial diversity increased during progression to bone loss. These findings further support the utilization of the periodontitis ligature model for microbial shift analysis under different experimental conditions.

The Role of Oral Fusobacterium nucleatum in Female Breast Cancer: A Systematic Review and Meta-Analysis

INTRODUCTION

Breast cancer is the world's most prevalent malignancy, with an increasing incidence and a predisposition for postpubertal females from all cultural and ethnic backgrounds. More recently, oral Fusobacterium nucleatum species have been observed in cancerous human breast tissue, drawing attention to the role of microbes in cancer pathogenesis.

OBJECTIVES

Investigating oral Fusobacterium nucleatum species as potential biomarkers for female-specific breast cancer.

METHODS

A systematic search in The Central Register of Controlled Trials, EMBASE, EBSCO, NCBI, and MEDLINE databases was undertaken from the 1st January, 1983-31st March, 2022. Articles included were in English and based on women between the ages of 18-96 years with confirmed gingivitis/periodontal disease and breast cancer diagnoses from registered specialists. Authors extracted data independently, and a meta-analysis of risk estimations measuring associations between oral Fusobacterium nucleatum species and female-specific breast cancer was elucidated via calculated relative risks and 95% confidence intervals.

RESULTS

AXIS tool analysis revealed 78.70% of articles with a positive correlation between oral Fusobacterium nucleatum and female-specific breast cancer. The risk of breast cancer development increased with significant levels of oral Fusobacterium nucleatum due to gingivitis/periodontitis (relative risk = 1.78, 95% confidence interval = 1.63-1.91). Low-moderate statistical heterogeneity was found (I 2 = 41.39%; P = 0.02), and the importance of periodontal status on breast cancer pathogenesis was determined (relative risk = 1.24, 95% confidence interval = 1.01-1.30).

CONCLUSIONS

Oral Fusobacterium nucleatum species are a risk factor for breast cancer development, thus elevating their biomarker potentiality.

Myocardial infarction risk is increased by periodontal pathobionts: a cross-sectional study

To establish the role of periodontal pathobionts as a risk factor for myocardial infarction, we examined the contribution of five periodontal pathobionts and their virulence genes' expressions to myocardial injury (Troponin-I) and coronary artery disease burden (SYNTAX-I scores) using hierarchical linear regression. Pathobiont loads in subgingival-plaques and intra-coronary-thrombi were compared. Troponin-I release increased with one 16S rRNA gene copy/ng DNA of Porphyromonas gingivalis (β = 6.8 × 10^-6, 95% CI = 1.1 × 10^-7-2.1 × 10^-5), one-fold increased expressions of fimA (β = 14.3, 95% CI = 1.5-27.1), bioF-3 (β = 7.8, 95% CI = 1.1-12.3), prtH (β = 1107.8, 95% CI = 235.6-2451.3), prtP (β = 6772.8, 95% CI = 2418.7-11,126.9), ltxA (β = 1811.8, 95% CI = 217.1-3840.8), cdtB (β = 568.3, 95% CI = 113.4-1250.1), all p < 0.05. SYNTAX-I score increased with one 16S rRNA gene copy/ng DNA of Porphyromonas gingivalis (β = 3.8 × 10^-9, 95% CI = 3.6 × 10^-10-1.8 × 10^-8), one-fold increased expressions of fimA (β = 1.2, 95% CI = 1.1-2.1), bioF-3 (β = 1.1, 95% CI = 1-5.2), prtP (β = 3, 95% CI = 1.3-4.6), ltxA (β = 1.5, 95% CI = 1.2-2.5), all p < 0.05. Within-subject Porphyromonas gingivalis and Tannerella forsythia from intra-coronary-thrombi and subgingival-plaques correlated (rho = 0.6, p < 0.05). Higher pathobiont load and/or upregulated virulence are risk factors for myocardial infarction.Trial registration: ClinicalTrials.gov Identifier: NCT04719026.

Biomarkers of Periodontitis and Its Differential DNA Methylation and Gene Expression in Immune Cells: A Systematic Review

The characteristic epigenetic profile of periodontitis found in peripheral leukocytes denotes its impact on systemic immunity. In fact, this profile not only stands for periodontitis as a low-grade inflammatory disease with systemic effects but also as an important source of potentially valuable clinical biomarkers of its systemic effects and susceptibility to other inflammatory conditions. Thus, we aimed to identify relevant genes tested as epigenetic systemic biomarkers in patients with periodontitis, based on the DNA methylation patterns and RNA expression profiles in peripheral immune cells. A detailed protocol was designed following the Preferred Reporting Items for Systematic Review and Meta-analysis -PRISMA guideline. Only cross-sectional and case-control studies that reported potential systemic biomarkers of periodontitis in peripheral immune cell types were included. DNA methylation was analyzed in leukocytes, and gene expression was in polymorphonuclear and mononuclear cells. Hypermethylation was found in TLR regulators genes: MAP3K7, MYD88, IL6R, RIPK2, FADD, IRAK1BP1, and PPARA in early stages of periodontitis, while advanced stages presented hypomethylation of these genes. TGFB1I1, VNN1, HLADRB4, and CXCL8 genes were differentially expressed in lymphocytes and monocytes of subjects with poorly controlled diabetes mellitus, dyslipidemia, and periodontitis in comparison with controls. The DAB2 gene was differentially overexpressed in periodontitis and dyslipidemia. Peripheral blood neutrophils in periodontitis showed differential expression in 163 genes. Periodontitis showed an increase in ceruloplasmin gene expression in polymorphonuclears in comparison with controls. Several genes highlight the role of the epigenetics of peripheral inflammatory cells in periodontitis that could be explored in blood as a source of biomarkers for routine testing.

Insight into the Relationship between Oral Microbiota and the Inflammatory Bowel Disease

Inflammatory bowel disease has been a growing concern of lots of people globally, including both adults and children. As a chronic inflammatory disease of the intestine, even though the etiology of inflammatory bowel disease is still unclear, the available evidence from clinic observations has suggested a close association with microorganisms. The oral microbiota possesses the characteristics of a large number and abundant species, second only to the intestinal microbiota in the human body; as a result, it successfully attracts the attention of researchers. The highly diverse commensal oral microbiota is not only a normal part of the oral cavity but also has a pronounced impact on the pathophysiology of general health. Numerous studies have shown the potential associations between the oral microbiota and inflammatory bowel disease. Inflammatory bowel disease can affect the composition of the oral microbiota and lead to a range of oral pathologies. In turn, there are a variety of oral microorganisms involved in the development and progression of inflammatory bowel disease, including Streptococcus spp., Fusobacterium nucleatum, Porphyromonas gingivalis, Campylobacter concisus, Klebsiella pneumoniae, Saccharibacteria (TM7), and Candida albicans. Based on the above analysis, the purpose of this review is to summarize this relationship of mutual influence and give further insight into the detection of flora as a target for the diagnosis and treatment of inflammatory bowel disease to open up a novel approach in future clinical practice.

The Ability of a Novel Trypsin-like Peptidase Activity Assay Kit to Detect Red-Complex Species

The trypsin-like peptidase activity assay kit measures the trypsin-like protease produced by three red-complex species, Porphyromonas gingivalis, Tannerella forsythia, and Treponema denticola, causing periodontitis, and detects the presence of these bacteria in samples. The purpose of this study was to investigate the relationship between the detection of TLPs by a novel TLP-AA, ADCHECK and the detection of red-complex pathogens by real-time PCR using tongue swabs from patients with periodontitis. The detection limit of trypsin-like protease activity by ADCHECK was validated using the culture supernatants of two different Porphyromonas gingivalis bacterial strains. Real-time PCR was performed to determine the number of red-complex species in the tongue coatings of patients with periodontal disease. Trypsin-like protease activity in tongue-swab samples was scored using ADCHECK. ADCHECK successfully detected trypsin-like protease activity in 103 Porphyromonas gingivalis bacterial strains. The specificity, positive predictive value, negative predictive value, and accuracy of ADCHECK for the presence of red-complex pathogens determined by real-time PCR were 90%, 97%, 98%, and 92%, respectively. ADCHECK is an effective tool for the detection of red-complex pathogens.

Cortisol Promotes Surface Translocation of Porphyromonas gingivalis

Studies are showing that the stress hormone cortisol can reach high levels in the gingival sulcus and induce shifts in the metatranscriptome of the oral microbiome. Interestingly, it has also been shown that cortisol can influence expression levels of Type IX Secretion System (T9SS) genes involved in gliding motility in bacteria belonging to the phylum Bacteroidota. The objective of this study was to determine if cortisol impacts gene expression and surface translocation of Porphyromonas gingivalis strain W50. To conduct these experiments, P. gingivalis was stabbed to the bottom of soft agar plates containing varying cortisol concentrations (0 μM, 0.13 μM, 1.3 μM, and 13 μM), and surface translocation on the subsurface was observed after 48 h of incubation. The results show that when grown with certain nutrients, i.e., in rich medium with the addition of sheep blood, lactate, or pyruvate, cortisol promotes migration of P. gingivalis in a concentration-dependent manner. To begin to examine the underlying mechanisms, quantitative PCR was used to evaluate differential expression of genes when P. gingivalis was exposed to cortisol. In particular, we focused on differential expression of T9SS-associated genes, including mfa5, since it was previously shown that Mfa5 is required for cell movement and cell-to-cell interactions. The data show that mfa5 is significantly up-regulated in the presence of cortisol. Moreover, an mfa5 deletion mutant showed less surface translocation compared to the wild-type P. gingivalis in the presence of cortisol, and the defects of the mfa5 deletion mutant were restored by complementation. Overall, cortisol can stimulate P. gingivalis surface translocation and this coincides with higher expression levels of T9SS-associated genes, which are known to be essential to gliding motility. Our findings support a high possibility that the stress hormone cortisol from the host can promote surface translocation and potentially virulence of P. gingivalis.

Candida and the Gram-positive trio: testing the vibe in the ICU patient microbiome using structural equation modelling of literature derived data

Background

Whether Candida interacts with Gram-positive bacteria, such as Staphylococcus aureus, coagulase negative Staphylococci (CNS) and Enterococci, to enhance their invasive potential from the microbiome of ICU patients remains unclear. Several effective anti-septic, antibiotic, anti-fungal, and non-decontamination based interventions studied for prevention of ventilator associated pneumonia (VAP) and other ICU acquired infections among patients receiving prolonged mechanical ventilation (MV) are known to variably impact Candida colonization. The collective observations within control and intervention groups from numerous ICU infection prevention studies enables tests of these postulated microbial interactions in the clinical context.

Methods

Four candidate generalized structural equation models (GSEM), each with Staphylococcus aureus, CNS and Enterococci colonization, defined as latent variables, were confronted with blood culture and respiratory tract isolate data derived from 460 groups of ICU patients receiving prolonged MV from 283 infection prevention studies.

Results

Introducing interaction terms between Candida colonization and each of S aureus (coefficient + 0.40; 95% confidence interval + 0.24 to + 0.55), CNS (+ 0.68; + 0.34 to + 1.0) and Enterococcal (+ 0.56; + 0.33 to + 0.79) colonization (all as latent variables) improved the fit for each model. The magnitude and significance level of the interaction terms were similar to the positive associations between exposure to topical antibiotic prophylaxis (TAP) on Enterococcal (+ 0.51; + 0.12 to + 0.89) and Candida colonization (+ 0.98; + 0.35 to + 1.61) versus the negative association of TAP with S aureus (− 0.45; − 0.70 to − 0.20) colonization and the negative association of anti-fungal exposure and Candida colonization (− 1.41; − 1.6 to − 0.72).

Conclusions

GSEM modelling of published ICU infection prevention data enables the postulated interactions between Candida and Gram-positive bacteria to be tested using clinically derived data. The optimal model implies interactions occurring in the human microbiome facilitating bacterial invasion and infection. This interaction might also account for the paradoxically high bacteremia incidences among studies of TAP in ICU patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12982-022-00116-9.

GSEM modelling of published ICU infection prevention data from > 250 studies enables a test of and provides support to the interaction between Candida and Gram-positive bacteria.

The various ICU infection prevention interventions may each broadly impact the patient microbiome.

Antimicrobial Effect of Moringa Oleifera L. and Red Pomegranate against Clinically Isolated Porphyromonas gingivalis: in vitro Study

Moringa oleifera L. and red pomegranate extracts have been reported to inhibit gram-positive facultative anaerobe growth and inhibit the formation of biofilm on tooth surfaces. The current study aimed to assess the antibacterial effect of M. oleifera L. and red pomegranate extracts and their combinations against Porphyromonas gingivalis. The antimicrobial sensitivity, minimum inhibition concentrations (MIC), and minimum bactericidal concentrations after treatment with the aqueous extracts of M. oleifera L. and red pomegranate as well as their combination against clinically isolated P. gingivalis were determined using agar well diffusion and two-fold serial dilution. The anti-biofilm activity of the extracts and their combination was evaluated using the tube adhesion method. The phytochemical analysis was carried out using gas chromatography-mass spectrometry. It was found that P. gingivalis was sensitive to aqueous extract of M. oleifera L. seeds and red pomegranate albedo, however, not to M. oleifera L. leaves and red pomegranate seeds. The MIC value of M. oleifera L. seeds, red pomegranate albedo, and their combination were obtained at 12.5 mg/ml, 6.25 mg/ml, and 3.12 mg/ml against P. gingivalis, respectively. The extract combination had the highest anti-biofilm effect than M. oleifera L. seeds and red pomegranate albedo aqueous extracts at the minimum concentrations of 6.25 mg/ml, 25 mg/ml, and 12.5 mg/ml, respectively. The combination of red pomegranate albedo and M. oleifera L. seeds showed superior antibacterial and anti-biofilm effects against P. gingivalis, followed by red pomegranate albedo and M. oleifera L. seeds. This may highlight a promising alternative to the traditional chemicals that can be used as an adjunct in the treatment of periodontal diseases.

Atypical cyclic di-AMP signaling is essential for Porphyromonas gingivalis growth and regulation of cell envelope homeostasis and virulence

Microbial pathogens employ signaling systems through cyclic (di-) nucleotide monophosphates serving as second messengers to increase fitness during pathogenesis. However, signaling schemes via second messengers in Porphyromonas gingivalis, a key Gram-negative anaerobic oral pathogen, remain unknown. Here, we report that among various ubiquitous second messengers, P. gingivalis strains predominantly synthesize bis-(3',5')-cyclic di-adenosine monophosphate (c-di-AMP), which is essential for their growth and survival. Our findings demonstrate an unusual regulation of c-di-AMP synthesis in P. gingivalis. P. gingivalis c-di-AMP phosphodiesterase (PDE) gene (pdepg) positively regulates c-di-AMP synthesis and impedes a decrease in c-di-AMP concentration despite encoding conserved amino acid motifs for phosphodiesterase activity. Instead, the predicted regulator gene cdaR, unrelated to the c-di-AMP PDE genes, serves as a potent negative regulator of c-di-AMP synthesis in this anaerobe. Further, our findings reveal that pdepg and cdaR are required to regulate the incorporation of ATP into c-di-AMP upon pyruvate utilization, leading to enhanced biofilm formation. We show that shifts in c-di-AMP signaling change the integrity and homeostasis of cell envelope, importantly, the structure and immunoreactivity of the lipopolysaccharide layer. Additionally, microbe-microbe interactions and the virulence potential of P. gingivalis were modulated by c-di-AMP. These studies provide the first glimpse into the scheme of second messenger signaling in P. gingivalis and perhaps other Bacteroidetes. Further, our findings indicate that c-di-AMP signaling promotes the fitness of the residents of the oral cavity and the development of a pathogenic community.

Multispecies biofilms in fermentation: Biofilm formation, microbial interactions, and communication

Food fermentation is driven by microorganisms, which usually coexist as multispecies biofilms. The activities and interactions of functional microorganisms and pathogenic bacteria in biofilms have important implications for the quality and safety of fermented foods. It was verified that the biofilm lifestyle benefited the fitness of microorganisms in harsh environments and intensified the cooperation and competition between biofilm members. This review focuses on multispecies biofilm formation, microbial interactions and communication in biofilms, and the application of multispecies biofilms in food fermentation. Microbial aggregation and adhesion are important steps in the early stage of multispecies biofilm formation. Different biofilm-forming abilities and strategies among microorganisms lead to several types of multispecies biofilm formation. The spatial distribution of multispecies biofilms reflects microbial interactions and biofilm function. Then, we discuss the intrinsic factors and external manifestations of multispecies biofilm system succession. Several typical interspecies cooperation and competition modes and mechanisms of microbial communication were reviewed in this review. The main limitations of the studies included in this review are the relatively small number of studies of biofilms formed by functional microorganisms during fermentation and the lack of direct evidence for the formation process of multispecies biofilms and microbial interactions and communication within biofilms. This review aims to provide the food industry with a sufficient understanding of multispecies biofilms in food fermentation. Practical Application: Meanwhile, it offers a reference value for better controlling and utilizing biofilms during food fermentation process, and the improvement of the yield, quality, and safety of fermented products including Chinese Baijiu, cheeese,kefir, soy sauce, kombucha, and fermented olive.