A rich diversity of gut microbiota is one of the secrets behind a healthy lifestyle from before we are even born.
Currently, the intestinal microbiota can be considered an organ in its own right because it plays an essential role in the proper functioning of our body.
As a whole, interactions between host and microbiota play a fundamental role in the health and well-being of the host. They are in charge of our immune system and digestion, and some bacteria have anti-inflammatory properties. It’s a living pharmacy inside our body that protects as well as heals.
Also called “intestinal flora,” the intestinal microbiota comprises billions of bacteria living in our digestive tract communities.
Its composition is unique, and it also evolves throughout life. Read on to learn more.
Table of Contents
- 1 A rich diversity of gut microbiota: Introduction
- 2 Protection of a child by the mother
- 3 A child’s oral exploration of the environment
- 4 Oral vs intestinal microbiota
- 5 Police methods to identify microbes
- 6 Bacteria in charge of digestion
- 7 The biodiversity of our microbiota is essential for our health
- 8 A rich diversity of gut microbiota: Conclusion
A rich diversity of gut microbiota: Introduction
By definition, the human microbiota is represented as the set of micro-organisms that live in the human body.
The composition of micro-organisms and the diversity of the intestinal microbiota are indicators of health.
The microbiota is set up from birth. It evolves according to factors such as a diet rich in fiber or antibiotic treatments.
The microbiota selected by the child will be unique and very personal, like the child’s fingerprints.
This article will discover the importance of a rich diversity of gut microbiota to stay healthy.
Protection of a child by the mother
Our digestive tract lacks microbes at birth, and its immune defenses are not very operational.
Little by little, a relationship will be established between the microbiota and its host, benefiting both parties.
The microbes will find in the digestive tract a favorable environment that is warm and rich in nutrients, allowing them to permanently establish themselves and consolidate their ecosystems.
The child will benefit from an enormous chemical factory thanks to the presence of these microbes.
This allows the child to adapt very quickly to changes in food and draw the maximum of nutrients, energy, and vitamins from the food absorbed.
For several months and while waiting for the maturation of its immune system, the infant will be protected against infections by its mother.
The child will be protected thanks to the antibodies transferred from the mother’s blood to the child’s blood via the umbilical cord.
After birth, that comes around thanks to the richness of breast milk in antibacterial substances and antibodies.
These particular antibodies of the “IgA” type are very present in the digestive mucosa.
These are the result of the maturation of the mother’s immune system in contact with her own digestive microbiota.
Then, the IgA in breast milk begins to sort out the germs that are trying to get into the child’s digestive tract.
Very quickly, the numerous bastions of lymphocytes located in the child’s intestinal wall will begin to activate in contact with the microbes that invade the digestive tract.
Finally, after they have reached maturity, they will finish the intestinal microbiota composition by adapting it to the child’s genetic characteristics, diet, and energy needs.
A child’s oral exploration of the environment
As soon as possible, children will start putting everything that comes within their reach in their mouths.
Reinforced by the diversification of their diet, this oral exploration of the environment will allow them to enrich their intestinal microbiota rather quickly despite the acidity of the stomach contents, which destroys many microbes.
The unstable variations observed before the child’s digestive immunity maturity will be followed by a stabilization of the intestinal microbiota.
The latter will acquire its definitive density and diversity before three.
However, in our constantly changing and turbulent world, many environmental factors can be expected to alter the composition of the gut microbiota, which will ultimately depend primarily on a diet and where the child lives on Earth.
But throughout the child’s life, the onset of severe digestive infections or the need for broad-spectrum antibiotic treatments can also upset the delicate and complex balance of the built-up microbiota.
- Lozupone, et al., Diversity, stability and resilience of the human gut microbiota, Nature, 2012
- Vatanen, et al., Genomic variation and strain-specific functional adaptation in the human gut microbiome during early life, Nature Microbiology, 2019
Oral vs intestinal microbiota
It is essential to know that the oral microbiota is very different from the intestinal microbiota.
In fact, oral germs try to spread to the digestive tract, but they come up against two types of defense:
- the acidity of the stomach in which few germs can survive
- unique antibodies, the immunoglobulins A, are present all along the digestive wall, which have the role of monitoring the territorial limits and destroying the imprudent germs which would cross the borders.
The microbiota is very poor in the stomach and in the initial part of the small intestine.
However, it will expand to reach enormous densities in the terminal small intestine, especially the large intestine.
The intestinal microbiota is the densest of all the microbiota in our body, with more than 100,000 billion micro-organisms weighing about 4 lbs.
- Costea, et al., Enterotypes in the landscape of gut microbial community composition, Nature Microbiology, 2018
- Dave, et al., The human gut microbiome: current knowledge, challenges, and future directions, Translational Research, 2012
Police methods to identify microbes
For a long time, research on intestinal microbes has been based on the culture of stool samples.
However, this technique did not allow for a precise study of the intestinal flora, most of which are anaerobic, i.e., they do not tolerate the presence of oxygen and die when leaving the intestine.
In the same way that the police are increasingly using DNA research to identify people who have been present at a crime scene, even dead microbial germs can be identified by the presence of the gene coding for ribosomal ribonucleic acid, which allows us to identify the different families of bacteria that populated a stool sample.
A study has identified in the intestinal flora of about 120 people a little more than 1,000 different bacterial species and about 160 species per person.
Recently, these numbers have been revised upwards with the evolution of biological techniques.
In another research on more than 12,000 samples, many previously unidentified species in the human gut microbiota were identified.
These identified bacteria carried hundreds of genes conferring new metabolic functions.
Many intestinal bacteria are harmless under normal conditions and play no direct role in the functioning of our body. They are called “saprophytes” and feed on our waste.
- Qin, et al., A human gut microbial gene catalogue established by metagenomic sequencing, Nature, 2010
- Forster, et al., A human gut bacterial genome and culture collection for improved metagenomic analyses, Nature Biotechnology, 2019
Bacteria in charge of digestion
There are also other bacteria called “symbiotic species” that collaborate in the physiology of our body. They are in charge of digestion:
- Amino acid synthesis
- Energy inputs
- The synthesis of vitamins (vitamins K and B8)
- Dietary fiber
These bacteria organize themselves into complex functional networks.
Studies have been carried out on people from different continents where researchers have identified 3 main groups (or enterotypes) of intestinal microbiota according to the bacteria most represented in them:
- Prevotella, which represent the bacteria involved in the synthesis of vitamin B1, essential for the functioning of the brain and involved in the absorption of sugars
- Bacteroids are bacteria involved in the synthesis of vitamin B7 and in the transformation of fats
- Ruminococus, a bacterium of the class Clostridiae involved in the metabolism of iron in the body.
These enterotypes were independent of geographic origin, gender, age, or possible health problems of the individuals.
- Landman & Quévrain, Gut microbiota: Description, role and pathophysiologic implications, La Revue de Médecine Interne, 2016
- Arumugam, et al., Enterotypes of the human gut microbiome, Nature, 2011
The biodiversity of our microbiota is essential for our health
Besides bacteria, the human intestinal microbiota also contains archaea, yeasts, and viruses, called “bacteriophages.”
These infect and kill bacteria and also contribute to the regulation of the composition of the microbiota. Hence the need of rich diversity of gut microbiota.
Yeasts constitute our intestinal mycobiome
Yeasts are single-celled microscopic fungi. The term “mycobiome” is defined as all yeast species identified in the gut microbiota.
The mycobiome represents less than 1% of the bacterial microbiota. In the oral cavity as well as in the digestive tract, the predominant genus of yeasts is Candida.
Interactions between the bacterial microbiota and the composition of the mycobiota probably exist.
Some components of the yeast wall are powerful immune stimulants and may also play a role in the occurrence of inflammatory diseases.
Viruses in our intestinal microbiota
The intestinal microbiota is also composed of viruses that are exceptionally involved in human diseases.
Most of these viruses are bacteriophages and attack bacteria exclusively and are 10 times more numerous than the other micro-organisms in our intestine.
Bacteria have developed a unique system to defend themselves against a predator of this magnitude, discovered in the late 1980s by a Japanese researcher (Atsuo Nakata of Osaka University).
In the genome of Escherichia coli bacteria, this researcher has identified repetitive DNA sequences that are identical in both directions, such as a palindrome (i.e., an identical word or phrase that can be read in both directions, like the word “madam”).
Years later, the researchers discovered that the DNA sequences between the palindromes came from bacteriophages that the bacteria had survived.
These bacteria used the complementary RNA produced from these DNA sequences integrated into their own genome to guide an enzyme to the corresponding DNA sequence of a potential bacteriophage attacker, severing it and thus disabling the virus.
The set of “repetitive sequences and viral genome” has been called CRISPR, which stands for Clustered Regularly Interspaced Short Palindromic Repeat.
This genetic defense mechanism has been copied by humans to design “scissors” that can modify DNA by cutting out some of its sequences and replacing them with different ones.
Experimentally, this technique has already been used to correct genetic anomalies in rodents. These experiments show the progress that “DNA scissors” could bring to human health, as well as the dangers to which they could expose humanity.
Namely, you could imagine how CRISPR and other technologies could potentially be used to create biological weapons targeting certain high-profile targets such as the US president, for example.
Fiction? Sure. But not unimaginable, is it? If you’re a potential high-profile target yourself, perhaps you’d do well to keep your genetic data to yourself, just to play it safe.
- Jiang & Doudna, CRISPR–Cas9 Structures and Mechanisms, Annual Review of Biophysics, 2017
- Hessel, et al., Hacking the President’s DNA, The Atlantic – Politics, 2012
Influence of the environment on the intestinal microbiota
By definition, biodiversity is a mark of the health of an environment. This is true not only for the Earth but also for a biotope.
The diversity and density of the intestinal flora are both witnesses and factors of good health for the human body.
The microbiota of adults who grew up in a rural environment, surrounded by many animals, is often more stable, richer and more diversified than the microbiota of children growing up in an urban environment, which would be more “hygienic.”
Generally, the gut microbiota is more homogeneous between individuals living in rural areas than in urban areas where inter-individual differences are marked.
The intestinal microbiota is also influenced by the microbial environment in which the person lives. As a result, there is a kind of “sharing” of gut microbes between people living in the same household.
A rich diversity of gut microbiota: Conclusion
The balance of the intestinal microbiota is essential for health.
Indeed, it is composed of many beneficial bacteria for our body, and other harmful bacteria.
Moreover, its richness and diversity play an essential role in maintaining this balance.
The intestinal microbiota is also essential for our immunity and digestion. Indeed, some bacteria have anti-inflammatory properties.
Therefore, it is vital to take care of your intestinal microbiota to keep your body healthy.