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Human oral cavity harbors the second most abundant microbiota after the gastrointestinal tract. The expanded Human Oral Microbiome Database (eHOMD) that was last updated on November 22, 2017, contains the information of approximately 772 prokaryotic species, where 70% is cultivable, and 30% belong to the uncultivable class of microorganisms along with whole genome sequences of 482 taxa. Out of 70% culturable species, 57% have already been assigned to their names. The 16S rDNA profiling of the healthy oral cavity categorized the inhabitant bacteria into six broad phyla, viz. Firmicutes, Actinobacteria, Proteobacteria, Fusobacteria, Bacteroidetes and Spirochaetes constituting 96% of total oral bacteria. These hidden oral micro-inhabitants exhibit a direct influence on human health, from host’s metabolism to immune responses. Altered oral microflora has been observed in several diseases such as diabetes, bacteremia, endocarditis, cancer, autoimmune disease and preterm births. Therefore, it becomes crucial to understand the oral microbial diversity and how it fluctuates under diseased/perturbed conditions. Advances in metagenomics and next-generation sequencing techniques generate rapid sequences and provide extensive information of inhabitant microorganisms of a niche. Thus, the retrieved information can be utilized for developing microbiome-based biomarkers for their use in early diagnosis of oral and associated diseases. Besides, several apex companies have shown keen interest in oral microbiome for its diagnostic and therapeutic potential indicating a vast market opportunity. This review gives an insight of various associated aspects of the human oral microbiome.

Following previous observations a statistically significant association between various types of spirochetes and Alzheimer's disease (AD) fulfilled Hill's criteria in favor of a causal relationship. If spirochetal infections can indeed cause AD, the pathological and biological hallmarks of AD should also occur in syphilitic dementia. To answer this question, observations and illustrations on the detection of spirochetes in the atrophic form of general paresis, which is known to be associated with slowly progressive dementia, were reviewed and compared with the characteristic pathology of AD. Historic observations and illustrations published in the first half of the 20th Century indeed confirm that the pathological hallmarks, which define AD, are also present in syphilitic dementia. Cortical spirochetal colonies are made up by innumerable tightly spiraled Treponema pallidum spirochetes, which are morphologically indistinguishable from senile plaques, using conventional light microscopy. Local brain amyloidosis also occurs in general paresis and, as in AD, corresponds to amyloid beta. These historic observations enable us to conclude that chronic spirochetal infections can cause dementia and reproduce the defining hallmarks of AD. They represent further evidence in support a causal relationship between various spirochetal infections and AD. They also indicate that local invasion of the brain by these helically shaped bacteria reproduce the filamentous pathology characteristic of AD. Chronic infection by spirochetes, and co-infection with other bacteria and viruses should be included in our current view on the etiology of AD. Prompt action is needed as AD might be prevented.

Background Current concepts suggest that a dysbiotic environment can promote ‘oral carcinomas.’ Microbiome studies on the oral cavity indicate changes in bacterial disposition in this condition. Yet, few focus on a lesser-known species, Treponema denticola , a motile periodontal pathogen, in addressing concerns related to oral carcinogenesis. Clinical studies find an enrichment of the Treponema genus in sites with oral cancer. Other research designs hint at Treponema denticola possessing both direct and indirect mechanisms to perpetrate damage in oral cancer. Methods We followed the Joanna Briggs Institute (JBI) methodology for this scoping review. The population, Concept and Context (PCC) were as follows: Population: adults with carcinomas in general/OSCC; Concept: T. denticola/Treponema and virulence factors; Context: Presence of T. denticola/Treponema and virulence factors in oral cavity tissues/fluids / or demonstrating role in carcinogenesis. The terms ‘ Adult OR population OR patient AND Treponema denticola OR T. denticola OR spirochete* OR treponema* AND oral cancer OR OSCC OR oral squamous cell carcinoma OR carcinoma OR metastasis OR epithelial-mesenchymal transition OR Oral cancer initiation , promotion , progression’ were adapted and searched across four different databases, retrieving all material published in English till 26 August 2024. Results Sixty-six articles were included in the scoping review following a full-text search, including 35 clinical studies, 21 reviews, 3 database studies, 4 in vitro studies, and 2 animal studies. Approximately 54% of the clinical studies found spirochetes or Trep o nema (genus/species) or its virulence factor abundant at cancer sites. Animal models also demonstrate the impact of Treponema denticola on tumour progression. Conclusions The genus Treponema and/or its virulence factors are detected in some oral carcinoma samples, indicating a possible association with advanced stages or deeper invasion. Future research can focus on its ability to induce malignant transformation and explore its potential as a candidate biomarker of oral carcinoma deserving validation.

•Chv chimeritopes contain 18 linear epitopes from different OspC variants.•Epitope ordering in OspC chimeritopes influences antibody responses.•Inter-epitope linkers were not required for optimal antibody responses.•Chv chimeritopes elicit broadly cross-reactive antibody.•Immunization induced antibody has potent bactericidal activity. Experimental Outer surface protein (Osp) C based subunit chimeritope vaccinogens for Lyme disease (LD) were assessed for immunogenicity, structure, ability to elicit antibody (Ab) responses to divergent OspC proteins, and bactericidal activity. Chimeritopes are chimeric epitope based proteins that consist of linear epitopes derived from multiple proteins or multiple variants of a protein. An inherent advantage to chimeritope vaccinogens is that they can be constructed to trigger broadly protective Ab responses. Three OspC chimeritope proteins were comparatively assessed: Chv1, Chv2 and Chv3. The Chv proteins possess the same set of 18 linear epitopes derived from 9 OspC type proteins but differ in the physical ordering of epitopes or by the presence or absence of linkers. All Chv proteins were immunogenic in mice and rats eliciting high titer Ab. Immunoblot and enzyme linked immunosorbent assays demonstrated that the Chv proteins elicit IgG that recognizes a diverse array of OspC type proteins. The panel included OspC proteins produced by N. American and European strains of the LD spirochetes. Rat anti-Chv antisera uniformly labeled intact, non-permeabilized Borreliella burgdorferi demonstrating that vaccinal Ab can bind to targets that are naturally presented on the spirochete cell surface. Vaccinal Ab also displayed potent complement dependent-Ab mediated killing activity. This study highlights the ability of OspC chimeritopes to serve as vaccinogens that trigger potentially broadly protective Ab responses. In addition to the current use of an OspC chimeritope in a canine LD vaccine, chimeritopes can serve as key components of human LD subunit vaccines.

Populations of key benthic habitat-forming octocoral species have declined significantly in the Mediterranean Sea due to mass mortality events caused by microbial disease outbreaks linked to high summer seawater temperatures. Recently, we showed that the microbial communities of these octocorals are relatively structured; however, our knowledge on the seasonal dynamics of these microbiomes is still limited. To investigate their seasonal stability, we collected four soft gorgonian species (Eunicella singularis, Eunicella cavolini, Eunicella verrucosa and Leptogorgia sarmentosa) and the precious red coral (Corallium rubrum) from two coastal locations with different terrestrial impact levels in the Mediterranean Sea, and used next-generation amplicon sequencing of the 16S rRNA gene. The microbiomes of all soft gorgonian species were dominated by the same ‘core microbiome’bacteria belonging to the Endozoicomonas and the Cellvibrionales clade BD1-7, whereas the red coral microbiome was primarily composed of ‘core’ Spirochaetes, Oceanospirillales ME2 and Parcubacteria. The associations with these bacterial taxa were relatively consistent over time at each location for each octocoral species. However, differences in microbiome composition and seasonal dynamics were observed between locations and could primarily be attributed to locally variant bacteria. Overall, our data provide further evidence of the intricate symbiotic relationships that exist between Mediterranean octocorals and their associated microbes, which are ancient and highly conserved over both space and time, and suggest regulation of the microbiome composition by the host, depending on local conditions.

The number of depressed people has increased worldwide. Dysfunction of the gut microbiota has been closely related to depression. The mechanism by which jasmine tea ameliorates depression via the brain-gut-microbiome (BGM) axis remains unclear. Here, the effects of jasmine tea on rats with depressive-like symptoms via the gut microbiome were investigated. We first established a chronic unpredictable mild stress (CUMS) rat model to induce depressive symptoms and measured the changes in depression-related indicators. Simultaneously, the changes in gut microbiota were investigated by 16S rRNA sequencing. Jasmine tea treatment improved depressive-like behaviors and neurotransmitters in CUMS rats. Jasmine tea increased the gut microbiota diversity and richness of depressed rats induced by CUMS. Spearman’s analysis showed correlations between the differential microbiota (Patescibacteria, Firmicutes, Bacteroidetes, Spirochaetes, Elusimicrobia, and Proteobacteria) and depressive-related indicators (BDNF, GLP-1, and 5-HT in the hippocampus and cerebral cortex). Combined with the correlation analysis of gut microbiota, the result indicated that jasmine tea could attenuate depression in rats via the brain- gut-microbiome axis.

The gastrointestinal microbiota of marine fishes plays important roles in host physiology and ecosystem processes yet remains poorly characterized. Here, we used 16S rRNA metabarcoding to examine the gastrointestinal microbiota of pompano dolphinfish (Coryphaena equiselis) collected from a neritic site (< 200 m) and a deep‐sea site (> 3800 m) in the South China Sea. Across sites, the microbial community was unexpectedly simplified and strongly dominated by Spirochaetes, particularly the genus Brachyspira. Because Brachyspira includes well‐documented pathogens of terrestrial animals, its high prevalence raises concern that pompano dolphinfish may act as reservoirs of potentially pathogenic bacteria with the capacity for trophic transfer. Coastal exposure may represent a critical source: Brachyspira was also detected at low levels in seawater eDNA from nearshore habitats, suggesting that dolphinfish could acquire these microbes during neritic stages and subsequently transport them into deep‐sea ecosystems. Functional predictions further revealed that gastrointestinal microbiota from both sites were closely associated with pathogenic processes, while neritic individuals additionally exhibited enrichment of functions linked to adaptation to anthropogenic stressors. Our findings underscore the ecological importance of dolphinfish microbiota as both a reservoir of potentially pathogenic lineages and a sensitive indicator of environmental stress in marine ecosystems. This study reveals an unexpectedly simplified, Brachyspira‐dominated gastrointestinal microbiota in pompano dolphinfish from both neritic and deep‐sea habitats of the South China Sea. Environmental DNA and functional analyses suggest these fish may acquire potential pathogens in anthropogenically influenced coastal waters and transport them offshore, highlighting a novel ecological route for pathogen dispersal in marine ecosystems.

Background:The diverse microbiome present in the rumen of ruminant animals facilitates the digestion of plant-based fiber. In this study, a shotgun metagenomic analysis of the microbes adhering to plant fiber in the camel rumen was undertaken to identify the key species contributing to lignocellulose degradation and short chain volatile fatty acids (VFA) fermentation.Results:The density of genes in the metagenome encoding glycoside hydrolases was estimated to be 25 per Mbp of assembled DNA, which is significantly greater than what has been reported in other sourced metagenomes, including cow rumen. There was also a substantial representation of sequences encoding scaffoldins, dockerins and cohesins, indicating the potential for cellulosome-mediated lignocellulose degradation. Binning of the assembled metagenome has enabled the definition of 65 high-quality genome bins which showed high diversity for lignocellulose degrading enzymes. Species associated to Bacteroidetes showed a high proportion of genes for debranching and oligosaccharide degrading enzymes, while those belonging to Firmicutes and Fibrobactereswere rich in cellulases and hemicellulases and thus these lineages were probably the key for ensuring the degradation of lignocellulose. The presence of many “polysaccharide utilization loci” (PULs) in Bacteroidetes genomes indicates their broad substrate specificity and high potential carbohydrate degradation ability. An analysis of VFA biosynthesis pathways showed that genes required for the synthesis of acetate were present in a range of species, except for Elusimicrobiota and Euryarchaeota . The production of propionate, exclusively via the succinate pathway, was carried out by species belonging to the phyla Bacteroidetes, Firmicutes, Spirochaetes and Fibrobacteres. Butyrate was generated via the butyrylCoA: acetate CoA-transferase pathway byBacteroidetes and Lentisphaerae species, but generally via the butyrate kinase pathway by Firmicutes species.Conclusion:The analysis confirmed the camel rumen’s microbiome as a dense and yet largely untapped source of enzymes with the potential to be used in a range of biotechnological processes including biofuel, fine chemicals and food processing industries.