In the communities topic, we already mentioned the community of symbionts living in the gastrointestinal tract of humans and other animals. Microorganisms that inhabit our stomach and intestines perform a number of important functions for us. In this topic, we will discuss the composition of the microbial community, its functions, and its scope in science.
What are microbial communities and their examples?
Microorganisms are extremely diverse. Microorganisms are the collective name for all those that cannot be seen with the naked eye – they include bacteria, archaea, protozoa, and some fungi. In nature, microorganisms primarily interact with other microorganisms, uniting in microbial communities. A microbial community is a collection of microorganisms with different roles interacting with each other for a long time in a certain place. The microbial community is characterized by a certain species composition, although their ratios among themselves change depending on changes in the environment.
The community of microorganisms that inhabit one particular area is called the microbiome. The microbiome can be formed by bacteria living in a small pond, in an aquarium, or anywhere else. The main interaction within the microbial community is trophic links that allow some organisms to feed on the metabolic products of others and provide exchange flows within the community. The metabolism of some microbes forms the substrate for the metabolism of others. Thus, clear and strong ties are built between the members of the community, and changes in these ties (for example, the complete disappearance of one species) will certainly affect others. It is trophic relationships that are the main characteristic of the microbial community. There are separate communities that independently produce a substance – for example, a photosynthetic community. There are communities of saprotrophs that decompose organic matter from the outside. There are communities that "live" on the influx of matter from outside – communities of heterotrophs.
Microbiome and microbiota
A good example of a microbiome composed of heterotrophs is the microbiota, the collection of microorganisms that inhabit the gastrointestinal tract of humans and animals. There are so many organisms there and the importance of the microbiota is so great that some scientists seriously consider it another organ of the body. The microbiota is also a community of microorganisms that are trophically related to each other.
The microbial environment of the gastrointestinal tract plays a particularly important role, you have probably heard of it as the intestinal flora. The microbiota "helps" us with a large number of issues. First of all, it is involved in the digestion of food and even the synthesis of those substances that the human body itself cannot synthesize, for example, vitamins from the B group and vitamin K.
Another role of the microbiota is to help the body "tune" the immune system. Bacteria create colonial resistance, closing the possibility for potentially pathogenic microorganisms to multiply uncontrollably inside the gastrointestinal tract and cause disease. In addition, having a huge number of potential external "enemies", the immune system learns to better recognize and respond to others. The immune system learns to ignore conditionally "good" bacteria, which allows it to be more effective.
A person is born completely sterile and immediately during childbirth, he begins to be populated by microbiota. According to various estimates, several thousand species live in the human gastrointestinal tract, and the species composition remains relatively stable throughout the life of the host organism. Sometimes the ratio of species (conditionally useful and conditionally pathogenic) can be disturbed, then this is called dysbiosis. There are always pathogenic organisms in the body, but most of our "inhabitants" can be both neutral and pathogenic – they can change their "behavior" due to changes in the environment (a change in a person's diet, a change in the composition of other bacteria, etc.). When dysbiosis, opportunistic pathogens can become a threat.
Significance of the microbiome for research
Over the past few decades, the interest of the scientific community in microbiota has increased, as it has become clear that microbes are directly involved in maintaining the homeostasis of the body and directly affect health. To study bacterial communities, the method of seeding on Petri dishes is most often used. They have been used since the dawn of experimental biology and continue to be used today. But due to the specific conditions of the gastrointestinal tract, not all bacteria can be studied in a laboratory environment. Some of them just can't live and form colonies on a Petri dish. Such organisms are called non-culturable, as opposed to culturable, which form colonies in a dish. For the cultivation of bacteria, their relationship to oxygen is also important – aerobes feel great in their presence, and anaerobes cannot grow in an oxygen environment. To grow bacteria per dish, scientists need a special medium containing those metabolites that bacteria need to live. Petri dishes are still used in a wide variety of research, from diversity determination (for example, inoculation of all microorganisms contained in a smear) to biotechnological experiments.
To detect the presence of many of them can only be guessed by performing a full genome sequencing – by following DNA traces. To assess species diversity, the RNA identification method is often used which is an analysis of 16-S ribosomal RNA is carried out. In addition, sometimes scientists want to study not the bacterium itself, but some of its metabolic products. Then the methods of metabolomics and proteomics are used – that is, the isolation of specific substances from a common solution.
Conclusion
A group of microorganisms living together is called a microbial community. If they inhabit a particular place, then it is a microbiome. An example of a microbiome is the human microbiota, the microorganisms that inhabit the gastrointestinal tract. It has many functions – from digestion to tuning the immune system and the synthesis of vitamins. Scientists are studying the microbiota in many ways as it becomes increasingly clear how much it affects our health.