Oral Microbiome: Getting to Know and Befriend Neighbors, a Biological Approach

Abstract

The oral microbiome, forming a biofilm that covers the oral structures, contains a high number of microorganisms. Biofilm formation starts from the salivary pellicle that allows bacterial adhesion-colonization-proliferation, co-aggregation and biofilm maturation in a complex microbial community. There is a constant bidirectional crosstalk between human host and its oral microbiome. The paper presents the fundamentals regarding the oral microbiome and its relationship to modulator factors, oral and systemic health. The modern studies of oral microorganisms and relationships with the host benefits are based on genomics, transcriptomics, proteomics and metabolomics. Pharmaceuticals such as antimicrobials, prebiotics, probiotics, surface active or abrasive agents and plant-derived ingredients may influence the oral microbiome. Many studies found associations between oral dysbiosis and systemic disorders, including autoimmune diseases, cardiovascular, diabetes, cancers and neurodegenerative disorders. We outline the general and individual factors influencing the host-microbial balance and the possibility to use the analysis of the oral microbiome in prevention, diagnosis and treatment in personalized medicine. Future therapies should take in account the restoration of the normal symbiotic relation with the oral microbiome.

Keywords: Oral Microbiome Database; amyloid; autoimmune diseases; biofilm; genomics; immune responses; metabolomics; oral diseases; systemic diseases.

Figure 1

The main factors influencing the evolvement of human microbiome over the lifespan (adapted after [5,6,13]). NICU—neonatal intensive care unit; CS—cesarean section.

Figure 2

Representation of molecular approaches for modern studies host–microbiome interactions. Several aspects of the Central Dogma of Molecular Biology—illustrating the flow of genetic information from DNA to mRNA to protein—can be assessed to study host–microorganism and microorganism–microorganism interactions at the molecular level in human populations (adapted after [6,18,19]). Legend: mRNA: messenger ribonucleic acids, ITS: Internal Transcribed Spacer, RT-PCR: Reverse Transcription—Polymerase Chain Reaction, MS: mass spectrometry, NMR spectroscopy: Nuclear Magnetic Resonance spectroscopy.

Figure 3

The types of biological samples that have been collected during the Human Microbiome Project population: saliva, palate, tonsils, throat, buccal mucosa (cheek), tongue soft tissues, supragingival dental plaque, etc. (adapted after [15,27]; metaniches and the composition of the oral microbiota associated with anatomically diverse oral regions: U-C metaniche: sublingual-cheek region, P-GCF metaniche: supragingival dental plaque—gingival crevicular fluid region, S-T-HP metaniche: saliva–tongue–hard palate region [28].

Figure 4

Types of main oral and main systemic diseases related to dysbiosis of the oral microbiome adapted after [6,30,43,44,63,64,65,69].