Our microbiome is composed of communities of bacteria, archaea, viruses, protozoans and fungi. It has greater complexity as well as a higher number of genes than the human genome itself. This community of microbes has even been described as a supporting organ in the human body.
Microbes and our human cells live in a mutually beneficial symbiotic relationship. However, the microbiome is dynamic and susceptible to changes such as diet, use of antibiotics and changes in homeostasis of the human body. Such changes affect the symbiotic relationship that exists between our body and microbiota. Pathogenic or ‘bad’ microbes are typically unable to gain control or large numbers until there is a change in our microbiome for the worse, which makes the human body more susceptible to diseases.
The majority of these microbes live in our gut with the second largest group being in our mouth. Microbial communities also reside on our skin and even in our genital tracts. All microbiome communities have the ability to affect our health, our partner’s health and even our future children’s health. The microbes in our gut, referred to as the gut microbiome, can be sampled using our poop to learn more about the large intestine or through an ingested capsule collected later that can capture small intestine samples. The oral and skin microbiome can be sampled using a swab. Similarly, the vaginal microbiome in women can be self-collected using a swab and can be analysed to understand microbe contribution to our health.
The first exposure to microorganisms for a human is in the birth canal during vaginal delivery. Most microbes that the infant is exposed to in the early days of life solely come from the mother through milk and contact through skin. As the infant grows, environmental exposures and diet changes can lead to the development of their own unique microbiome, which is very instrumental in training a child’s immune cells and eventually dictates many facets of adult human health.
Microbes also have a broader effect on our health, contributing to our nutrition by producing metabolites, nutrients, and vitamins. They also affect metabolic functions by influencing our fat storage, they can protect our body against pathogens and even help in the education of our immune system. They have also been shown to affect our physiological functions directly and indirectly by influencing brain function and human behaviour, making it an indispensable organ of our body.
However, pathogenic microbes can displace beneficial microbes over time, changing metabolic processes that could result in an abnormal immune response against our body. Hence, even autoimmune diseases such as diabetes, rheumatoid arthritis, muscular dystrophy, multiple sclerosis, and fibromyalgia have been associated with dysfunction in the microbiome. Inheritance of autoimmune diseases is described less by human DNA inheritance and more by inheritance of a familial microbiome.