The Key Types Of Bacteria Found In Our Gut & Their Functions

January 11, 2023
The Key Types Of Bacteria Found In Our Gut & Their Functions

Our human body is full of microbes, such as bacteria, viruses, fungi, protozoa, and eukaryotes. Over the course of millennia, humans have co-evolved and lived in symbiosis with these microscopic neighbours; we scratch their backs, and vice versa.


Bacterial genes outnumber our human cells by 100:1. However, they communicate together, influencing our intestinal, metabolic, and immune health. In this article, we will discover the types of bacteria in our gut, their respective functions, and how they can influence our overall health.


1. Commensal bacteria

This is the largest and most important variant of microbes that are typically found in the large intestine. While there are other beneficial bacteria, such as probiotics, the commensal bacteria are, most of the time, equally beneficial to our health.


In return for nutrients to feed on and an environment to thrive in, the commensal bacteria perform several vital health functions, such as protecting our body from pathogens, metabolising indigestible fibres, training immune cells to function, and maintaining the gut lining’s health. Hence, the fewer commensal bacteria in the gut, the higher the chance of an imbalanced gut microbiome, also known as dysbiosis, which increases the opportunity for a pathogenic encounter.


2. Opportunistic pathogens

These are bacteria with the capability to cause disease, given the right situation, such as in individuals who are immunocompromised. Typically, opportunistic pathogens exist even in healthy individuals without causing any adverse effects. However, environmental changes to the gut microbiome can result in them causing issues.


One such example is Clostridium difficile (C.diff), an opportunistic pathogen that causes chronic diarrhoea symptoms and infection. A healthy individual may have a small amount of C.diff in their gut microbiome, which remains harmless due to the commensal bacteria’s protective effect. However, disruption to the diversity of our gut microbiome can trigger an overgrowth of C.diff. One fundamental cause of such an infection is the consumption of antibiotics, which destroys both good and bad bacteria, reducing colonisation resistance and making us vulnerable to any pathogenic invasion.


3. Probiotics

They are ideal for commensal bacteria support, especially when there is trouble. Just as external microbes can enter our body and cause diseases and conditions, beneficial bacteria like probiotics can also be taken to support the commensal bacteria. Probiotics are live microorganisms that can be found in fermented foods, such as kimchi or sauerkraut.


Probiotics rarely are permanently found in our gut. However, they do interact with the commensal bacteria while going through our GI tract. Probiotics offer similar health benefits as commensal bacteria. They help to regulate our immune system, metabolise indigestible fibres, and ward off pathogens. They are usually taken with prebiotics, which is an indigestible fibre that is an ideal food source for beneficial bacteria. When taken with prebiotics, they are called synbiotics.



Our body is home to a wide variety of microbes, both good and bad. While commensal bacteria generally protect our body against pathogens, they can, given the right situation, become pathogenic themselves, resulting in the development of opportunistic pathogens. Hence, it is vital that we consume a well-balanced diet that is rich in fibre, probiotics, and prebiotics. Additionally, regular gut health check-ups are recommended or as soon as you experience vomiting symptomsIBS symptoms, or any other that warrant an immediate gastroenterology visit.


Do not wait till it is too late.


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