Our mouth is an exceptionally complex habitat where numerous microorganisms including bacteria, fungi, viruses and protozoa exist in a dynamic and a balanced symbiotic micro-ecology.
In this symbiotic micro-ecology, the microbiome receive a secure, moist and nutritious environment while the microbiota confer many important benefits.
The oral cavity microbiota harbours over 700 species of bacteria. Did you know that it is considered the second largest and diverse after the human gut!
The oral cavity has two types of surfaces on which bacteria can colonize: the hard and the soft tissues of teeth and the oral mucosa, respectively. The teeth, tongue, cheeks, gingival sulcus, tonsils, hard palate and soft palate provide a rich environment in which microorganisms can flourish. The surfaces of the oral cavity are coated with a plethora of bacteria termed as the proverbial bacterial biofilm.
An ideal environment is provided by the oral cavity and associated nasopharyngeal regions for the growth of microorganisms. On an average, the normal temperature of the oral cavity is 37°C. This provides bacteria a stable environment to survive. Saliva also has a stable pH of 6.5–7 which in turn is a favourable pH for most species of bacteria.
Different surfaces in the mouth are colonized preferentially by the oral bacteria due to specific adhesins on their surface which bind to complementary receptors on a particular surface inside the mouth e.g, teeth surfaces, mucosal surface, etc.
Being at health or progression towards a disease is critically influenced by the microbiota. The oral microbiome usually exists in the form of a biofilm. It plays a crucial role in maintaining oral homeostasis and protecting the oral cavity. Many a times they help in the development of our defence mechanisms early in life. These microbiota also fights against potential pathogens and prevent them from colonising available surfaces; thus, preventing disease development. They also help in regulating the cardiovascular system and contribute as the initiators of our food digestion.
Thus, in several ways the oral microbiome is crucial in maintaining oral as well as systemic health.
Oral microbiome was first identified by the Dutchman Antony van Leeuwenhoek. He was called the Father of Microbiology and a pioneer who discovered both protists and bacteria. He observed his own dental plaque and reported “little living animalcules prettily moving.”
Human microbiome primarily consists of :
- a core microbiome -common to all the individuals and consists of predominant species that exist at different sites of the body under healthy conditions
- a variable microbiome – exclusive and unique to individuals which evolve in response to unique lifestyle, genotypic determinants and physiological differences
A unique set of oral microbiome is known as “Oral Signature”. It differs from one individual to another exactly similar to a person’s exclusive sign.
Highly individualized microbiome that has evolved to promote oral health exists in a dynamic balance with the host. Any micro-ecological changes to the biology of the mouth (known as dysbiosis) caused by changes in the host’s diet and lifestyle or status of the immune system may drive deleterious shifts in the composition or metabolic activity of the oral microbiome.
Previously, studying the microbiome was limited to the conventional culture-dependent techniques. The abundant microflora present in the oral cavity could not be cultured. Hence, studying the microbiome was difficult.
The emergence of new genomic technologies including next-generation sequencing and bioinformatics has revealed the complexities of the oral microbiome. It has provided a powerful means of studying the microbiome.
The huge increase in recent knowledge on the ecology and microbiology of the oral cavity generated by ‘OMIC’ technologies e.g. metagenomics, culturomics* and molecular analysis methods, such as DNA-DNA hybridization or immunoblot techniques, may indeed be clinically translated to support patient care, in terms of prevention, monitoring, risk classification or early diagnosis.
The identified clinical applications may not only include dental caries and periodontal disease, but also dental implants and orthodontics. Population-based applications may include systemic health, pregnancy and elderly populations.
The so called “oral signature” can be used to evaluate the susceptibility to contract or resistance of a person to the contraction of a wide range of pathologies, apparently not connected with oral health. Such evidence will possibly lead to study therapeutic approaches to eradicate species considered at risk or colonization with species considered protective.
A promising future with diagnostics leading us towards the era of “Personalised Dentistry”!
PS:
*Metagenomics is a set of techniques which detects bacteria that cannot be cultured. It also identifies the genomic diversity of microbes by applying the power of genomic analysis to the entire community of microbes
**Culturomics is a new technique that deals with the use of different culture conditions and matrix-assisted laser desorption ionization-time of flight mass spectrometry, which provides a deep increase in the number of detectable bacteria
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