What is the Gut Microbiota?

November 01, 2021

Introduction To The Gut Microbiota

The human digestive system is simple and complex at the same time. It harbors communities of microorganisms, some of which are beneficial while others are not. Many factors contribute to the establishment of these bacteria in the gut. The food we eat is one major contributor. According to a study(1), about 60 tons (60,000 kg) of food passes through the gastrointestinal (GI) tract in an average lifespan. An abundance of microorganisms and substrates are carried along with the food. These foreign microorganisms, along with the innate microorganisms found in our gut, make up the gut microbiota.

What Is Gut Microbiota?

Biota is coined from the Latin word biote meaning life. Gut microbiota is the term used for describing the microorganism flora in the gut. To put it simply, it represents all microorganisms present in the gut. They include different types of microorganisms which form symbiotic relationships with the host. Studies(2) have shown that there are 1014 of these organisms present in the GI tract, making it approximately ten times more than the number of human cells in the body. Due to these symbiotic relationships between the microorganisms and the human cells, the human body is considered a superorganism.

Function Of the Gut Microbiota

The gut microbiota has many functions in the human body, such as aiding in the absorption of nutrients, controlling the population of pathogens, supporting neurological functions and influencing key metabolic processes.

Absorption of nutrients
The gut microbiota helps in the fermentation of food molecules such as prebiotic and production of some nutrients like vitamin B and K. It also influences the metabolism of nutrients due to its interactions with the epithelial receptors along the GI lining.(3)

Controlling population of pathogens
The competitive-exclusion effect of the gut microbiome is one of the many ways it limits the growth of pathogens in the gut. The gut microbiota competes with these foreign microorganisms for nutrients and at the same time, it secretes antimicrobial compounds such as bacteriocins, which prevent the foreign microorganisms from flourishing and harming the host.(3)

Supporting neurological functions
The digestive tract and the brain communicate with each other through a connection known as the gut-brain axis. Messages in the forms of hormonal, immunological, and neural signals travel back and forth between the central nervous system and the gut via this axis. This enables the brain to control certain GI functions such as movement of food through the digestive tract and the release of digestive enzymes. Gut microbiota produces substances that may affect these transmissions.(3)

Influencing key metabolic processes
The gut microbiota is also able to influence key metabolic processes such as insulin sensitivity, glucose tolerance, fat storage, and appetite, mainly through the regulation of gut hormones release. (4)

References

1. B. S. Bengmark “Ecological control of the gastrointestinal tract. The role of probiotic flora” Gut 42(1):2-7

2. R. Gill, et al. “Metagenomic Analysis of the Human Distal Gut Microbiome” Science 312(5778):1355-9

3. M.Jandhyala, et al. "Role of the normal gut microbiota" World Journal of Gastroenterology. 2015 Aug; 21(29): 8787–8803.

4. M. Martin, et al. "The Influence of the Gut Microbiome on Host Metabolism Through the Regulation of Gut Hormone Release" Frontiers in Physiology. 2019 Apr; 10: 428.