Metagenomic and massive sequencing techniques have revolutionized the study of microorganisms that coexist with humans, known globally as microbiome, which we can qualify as an organ, not physical, but functional.
In the laboratory of Alex Mira, from FISABIO Foundation (Valencia), have developed different "omics" techniques to study the microbial communities in the mouth, stomach, respiratory tract, breast milk or intestine, both in health and in disease. These studies have allowed, on the one hand, determine the etiology of diseases such as dental caries or periodontitis, and on the other hand, identify bacteria that function as biomarkers colorectal cancer, as well as selecting bacteria that can function as probiotics against different diseases.
Mira has shown examples of how the human microbiome is actually a very complex set of ecosystems in constant relationship and balance with our body. When that balance is broken and the normal microbiome is disrupted (disbiosis) is related to various pathologies. Each niche of the body has a different microbial complexity, so that a microbial community adapted to that specific environment is selected: the intestinal microbiota is different from the fecal, breast milk, skin, mouth or vagina microbiota. There is no sterile niche in our body: there are bacteria in the stomach or in breast milk, for example.
He has detailed his studies on the oral microbiota and the dental plaque ecosystem. From a diet rich in vegetables, the bacteria in the mouth are able to reduce nitrate to nitrite. Our own body can use this nitrite to produce nitric oxide with a number of functions, such as cardiovascular effects. Saliva concentrates nitrate (there may be 10 times more than in the bloodstream), which is available to oral bacteria that generate nitrite, which is used by our bodies to produce nitric oxide. A fascinating example of symbiosis between our bacteria and our body.
On the other hand, when the bacteria are not in their specific niche, some pathology can occur. For example, it has shown the relationship between periodontitis (bleeding gums) that facilitate the passage of bacteria from the mouth to the bloodstream and premature labor. Another example of clinical application is the comparative study of DNA from oral samples of people with and without cavities, which revealed a high frequency of a new species, baptized as Streptococcus dentisani, which neutralizes acid and is already being tested as an anticaries probiotic in clinical trials.
Other examples, such as the production of short-chain fatty acids and neurotransmitters by intestinal bacteria, or how some microbiota bacteria can modulate the efficacy and toxicity of chemotherapy and immunotherapy treatments, highlight the importance of our microbes for the Health.
Summary prepared by Ignacio López-Goñi, from the University of Navarra.
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