Journal of Bacteriology & Parasitology

The Role of Commensal Bacteria in Human Health and Disease

Sophie Tremblay^* Department of Biomedical Sciences, University de Montreal, Montreal, Canada
^*Correspondence: Sophie Tremblay, Department of Biomedical Sciences, University de Montreal, Montreal, Canada, Email:

Received: 27-Jan-2025, Manuscript No. JBP-25-28652; Editor assigned: 30-Jan-2025, Pre QC No. JBP-25-28652(PQ); Reviewed: 13-Feb-2025, QC No. JBP-25-28652; Revised: 20-Feb-2025, Manuscript No. JBP-25-28652(R); Published: 27-Feb-2025, DOI: 10.35248/2155-9597.25.16.527

Description

Commensal bacteria are the microorganisms that reside on and within the human body without causing harm under normal conditions. In fact, they play an essential role in maintaining human health. These bacteria, often referred to as the microbiota, are found in various body sites including the skin, mouth, respiratory tract, urogenital tract and most abundantly, the gastrointestinal tract. The balance between the host and these microbes is delicately maintained and disruptions to this equilibrium can contribute to a range of diseases.

The human gut hosts trillions of commensal bacteria, which are integral to the digestive process. They assist in breaking down complex carbohydrates, synthesizing essential vitamins such as B12 and K and enhancing the absorption of minerals. Beyond digestion, these microbes produce Short-Chain Fatty Acids (SCFAs) like butyrate, acetate and propionate, which serve as energy sources for colon cells and have anti-inflammatory properties. By producing these beneficial compounds, commensal bacteria help maintain the integrity of the intestinal barrier and prevent systemic inflammation.

One of the most critical roles of commensal bacteria is the modulation of the immune system. From infancy, the microbiota educates the immune system by training it to distinguish between harmful and harmless agents. This helps to prevent overactive immune responses, which could lead to allergies or autoimmune diseases. Commensal bacteria also occupy ecological niches within the body, outcompeting pathogenic microbes for resources and space, thus preventing colonization by disease-causing organisms. This phenomenon, known as colonization resistance, is an important natural defense mechanism.

However, the relationship between commensal bacteria and the host is not always beneficial. When the balance of the microbiota is disrupted a condition known as dysbiosis commensals can contribute to disease. Dysbiosis may occur due to factors such as antibiotic use, poor diet, stress, or infection. In such cases, protective bacteria may be depleted and opportunistic microbes may proliferate, increasing the risk of infections and inflammation. For example, overgrowth of Clostridioides difficile following antibiotic treatment can lead to severe colitis, illustrating how the loss of microbial diversity can have harmful consequences.

Dysbiosis has also been implicated in a wide array of chronic conditions. Inflammatory bowel diseases like Cohn’s disease and ulcerative colitis have been linked to imbalances in gut bacteria, where certain pro-inflammatory species become more abundant. Similarly, metabolic disorders such as obesity and type 2 diabetes have been associated with alterations in the composition of the gut microbiota, which may influence energy extraction from food and insulin sensitivity. Even neuropsychiatric disorders, including depression and anxiety, are increasingly being connected to the gut-brain axis a bidirectional communication network where the microbiota is believed to influence brain function through metabolic, immune and neural pathways.

The protective and pathological roles of commensal bacteria have led to growing interest in therapies aimed at restoring or enhancing the microbiota. Probiotics, which are live beneficial bacteria and prebiotics, which are non-digestible food components that nourish them, are commonly used to promote gut health. More advanced strategies include Fecal Microbiota Transplantation (FMT), where stool from a healthy donor is transferred to a patient to treat conditions such as recurrent C. difficile infection. Research into personalized microbiome-based treatments is ongoing and locks potential for managing a variety of health issues.