What is the microbiome?

Authors: Sharon Jang , Vanessa Mok , Dominik Zbogar | Reviewer: Phillip Popovich | Published: 5 May 2020 | Updated: ~

Illustration accompanying What is the microbiome?

Examples of bacteria that can be found in the digestive system.1-4

The microbiome refers to the trillions of viruses, fungi, and bacteria living all over the body. Although you may see the terms “microbiota” and “microbiome” sometimes used interchangeably, the microbiome technically refers to the genetic makeup (i.e. the DNA) of these organisms, while the microbiota refers to the organisms themselves. The core microbiota in humans is similar between people, however each of us has their own distinct variation of bacteria, viruses, and fungi that comprises their microbiota. These organisms exist in many areas of the body, including on the skin, in the nose, in the vagina, and in the bladder. However, microbiota have the highest density and variation in the large intestine.

Our past view of microbiota was focused on their potential to cause infection. However, more recent research has shown that microbiota play a substantial role in normal development and daily body functions. The greater the diversity or variation of the microbiota, the healthier and more resilient it is. The opposite has been associated with negative long-term effects on diseases later in life. Although research on the microbiome is still emerging, researchers have discovered that the microbiome is responsible for:

  • Preventing the growth of other harmful organisms
  • Stimulating the immune system to help fight off infections
  • Preventing the development of allergies
  • Food digestion and nutrient absorption
  • Sugar and fat metabolism
  • Brain development
  • Drug metabolism

In recent years, the microbiome has gained a lot of interest in research. This is partly due to new technology which allow scientists to observe the DNA of bacteria, resulting in a more specific analysis. Bacteria is primarily prevalent in the intestines, and amount to 10 times more than all the cells in the human body. This adds up to 1-3% of body mass, or 2-6 lbs of your weight. This article will focus on the gut microbiota, specifically the bacterial component of the microbiota, as most of the research on the microbiome thus far has focused on bacteria rather than fungi and viruses.

Development of the gut microbiome

While recent studies have shown that transmission of bacteria from the mother to the fetus is possible and occurs even before birth, it appears that much of the gut microbiome is established during delivery as the baby comes into contact with the microbes present in the mother’s birth canal and skin. Hence, a baby that is born through a C-section will have a different microbial composition. The gut microbiome continues to change due to organisms in the breastmilk; formula-fed infants will present with a different gut microbiome. The diversity of the microbiome increases until it resembles that of an adult around 3 years of age when a solid food diet is established.