gut microbiota
Intestine in hands. Microbiome of digestive system. Probiotic treatment. Probiotic cells for immunity. Digestive health. Studying action of probiotics. Microflora of intestinal tract

The collection of trillions of microbes, specifically bacteria, residing in the human gut is known as the human gut microbiota. It is accompanied by the microbiome, which refers to the overall environment that these microbes inhabit. While most of the body’s microbes serve a beneficial purpose, an imbalance can lead to their harmful effects.

The terms microbiota and microbiome are often used interchangeably by people, but this usage is incorrect.

The microbiota encompasses a diverse range of microorganisms such as bacteria, viruses, fungi, and other tiny organisms found within a specific environment, like the digestive tract of humans.

On the other hand, the microbiome encompasses not only the microorganisms present in the body but also includes their genetic material (genomes) and the surrounding environmental conditions.

This article aims to examine and clarify the distinctions between the microbiota and microbiome.

What is the Human Microbiome?

Every individual maintains a symbiotic relationship with approximately 10 trillion to 100 trillion microbial cells. Some studies suggest that the number of microbial cells in the body is around 10 times greater than human cells, while others propose a more balanced ratio of 1:1.

As long as the body remains in a healthy state, this symbiotic relationship between microbes and their hosts proves beneficial. The human microbiota is estimated to consist of over 1,000 different species of microorganisms, although specific numbers may vary.

The composition of the human biome can significantly differ among individuals, and various regions of the body harbour distinct microbial communities. For instance, the oral cavity, genital organs, skin, gastrointestinal system, and respiratory tract all contain numerous microbial cells. However, the types, quantities, and functions of these microorganisms vary across these different locations.

What is the Gut Microbiota?

The human gut microbiota is an extensive and intricate community of microorganisms that exerts a profound impact on human health. In the past, the gut microbiota was commonly referred to as the microflora of the gut.

The gut microbiota plays a crucial role in a wide range of bodily functions, which include:

  • Extracting energy from digested food
  • Safeguarding against harmful pathogens
  • Regulating immune function
  • Strengthening the biochemical barriers of the gut and intestine

Alterations in the composition of the gut microbiota can significantly influence these essential functions.

While the gut houses beneficial bacteria, it can also harbor harmful bacteria that can enter the gastrointestinal (GI) tract and cause infections. These infections encompass various GI diseases, including food poisoning, which manifest as symptoms such as diarrhea and vomiting.

Why is the Human Microbiota Important?

Microorganisms play a crucial role in sustaining human life and perform a multitude of essential functions. Interestingly, the bacterial cell count in the gastrointestinal system is estimated to be approximately 10 times higher than that of human cells.

Numerous studies indicate that the composition of bacterial populations in the gut is associated with various health conditions and disruptions, including:

  • Asthma
  • Autistic spectrum disorder
  • Cancer
  • Celiac disease
  • Diabetes
  • Eczema
  • Heart disease
  • Malnutrition
  • Multiple sclerosis
  • Obesity

These findings highlight the potential impact of bacterial populations on human health and the significance of maintaining a balanced microbiota


In addition to their role in energy absorption from food, gut microbes are vital in facilitating nutrient absorption. They assist the body in breaking down complex molecules found in foods like meats and vegetables. For instance, gut bacteria are instrumental in breaking down plant cellulose, which the body cannot digest on its own.

gut microbiota

Moreover, gut microbes have the ability to influence food cravings and feelings of satiety through their metabolic activities.

It is worth noting that the diversity of an individual’s diet has an impact on the diversity of their gut microbiota. Research suggests that the variety of foods consumed can influence the richness and abundance of microbial species in the gut.


Recent studies have indicated that the initial exposure to microbes may actually occur before birth, according to trusted sources. This early colonisation by microbes is crucial as it plays a significant role in the development of the adaptive immune system. The adaptive immune system learns how to respond to various microbes through exposure, enabling a faster and more efficient defence against disease-causing organisms.

The formation of an individual’s gut microbiota begins with the first encounters of microbial guests and usually reaches a stable and diverse composition by the age of 3 to 5 years, as per trusted sources. Disruptions or disturbances during these early exposures can potentially hinder the normal development of the gut microbiota. It highlights the importance of early microbial interactions in shaping a healthy microbiota.


The gut microbiota and the brain maintain a constant line of communication through a connection known as the gut-brain axis. While the gut-brain axis primarily influences intestinal function, researchers have also discovered associations between the gut microbiota and psychological disorders, including depression and Autism Spectrum Disorder (ASD), as indicated by trusted sources. These connections suggest that the gut microbiota has the potential to impact not only gastrointestinal health but also mental well-being.


Research indicates that bacterial populations residing in the gastrointestinal system have a significant impact on the development of gut-related conditions, such as inflammatory bowel diseases (IBD) like Crohn’s disease and ulcerative colitis. Additionally, low microbial diversity in the gut has been associated with obesity and type 2 diabetes.

Furthermore, the status of the gut microbiota is linked to metabolic syndrome, a cluster of conditions that increase the risk of heart disease, stroke, and type 2 diabetes. Making dietary changes by incorporating prebiotics, probiotics, and other supplements has shown potential in reducing these risk factors.

It is worth noting that disturbing the microbiota through the use of antibiotics can lead to diseases, including infections that become resistant to antibiotics.

The microbiota also plays a vital role in preventing the excessive growth of externally introduced populations in the intestines, which can otherwise cause disease. The “good” bacteria compete with the “bad” bacteria, and some even release anti-inflammatory compounds, further contributing to maintaining a healthy gut environment.

Microbiome Research

Huge investment has gone into research about microbial populations in the body and their genetics, exploring links with health and disease.

The project helped establish links between specific microbial compositions and diseases across demographics. Due to the project, researchers can better understand the genetic composition of the gut microbiota and establish methods of classifying and analyzing their varying microbial compositions.


The gut microbiota refers to the collection of microorganisms, including bacteria, fungi, viruses, and other organisms, present in a person’s gastrointestinal system. It exists in a mutually beneficial relationship with the human digestive system and plays important roles in energy extraction, digestion, and immune defence.

Apart from the gut microbiota, there are various other microbiotas in the body, such as those found in the oral and vaginal cavities, colon, and skin. The human microbiome, on the other hand, encompasses the overall composition of all microbiotas present in the body.

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