Let’s Explore the World of Human Microbiomes

Human Microbiomes

The microbiome is a myriad community of microbes, classified genetically, living in and on the human body, whereas, ‘microbiota’ is a description of the organisms themselves. However, the terms were originally synonymous and are still sometimes used interchangeably. It is due to this genetic information that the microbiome is often referred to as ‘the second genome project’. Every human being carries approximately 3 lbs (about the same weight as their brain) of microbes around that intimately affect their whole life. They are our fellow travellers and without them, we could not survive.

The reason that scientists originally began to study the genetic makeup of the microbiota is that the original method of growing microbes in a petri dish didn’t adequently reveal the diversity of the microbial population. This is because the majority of microbes are very particular about where they live and thus, cannot be cultured. Scientists once believed that E.coli made up the bulk of the microbes in the gut when fact, it happens to be very easy to culture outside the body and is actually present in only small numbers in a healthy gut.

The human body is, from a microbes point of view, an ecosystem of habitats supporting distinct groups of microorganisms that characteristically choose to live in or on only one part of the body. This is much the same principle as biogeography; certain animals are only found in certain landscapes. In the case of the mouth, for instance, one side of a tooth can support a completely different community of microbes than the opposite side. In other words, there are several different habitats sustaining varying groups of microbes in the human mouth.

The diversity of microbes in the gut alone is far larger and more complex than the diversity of life in any rainforest. The numbers of microbes in the human body and the implications of these numbers are truly astounding. For instance:

  • There are 10 trillion human cells in the human body, but there are 100 trillion microbial cells. This makes you roughly 10% human at a cellular level.
  • You have 20,000 human genes, but there are between 2-20 million microbial genes in the human microbiome. Genetically speaking, you are 0.1 to 1% human.
  • Any two people are 99.99% genetically similar, but there is a 90% difference in the microbiome of any two people. Your microbiome is far more individual than you are!

These numbers are important for a number of reasons. They show that your microbiome is a huge part of who you are – including how healthy you are and how you interact with the world around you.

Although study of the human microbiome is still in its infancy (primarily started in earnest in the ‘90’s), it is already showing immense promise in the areas of health, medicine and psychology. The microbiota of the gut are the most numerous and most studied of all the microbes in the body. One of the reasons is that it is the easiest to study, through the taking of stool samples, which is non-invasive and holds valuable keys to what is happening inside the body.

In fact, if you want to know about your own gut microbiome, you can take part in one of several studies being conducted to collect data for this vital field of study. The American Gut Project, crowdsourced on Kickstarter, was the first project of its kind. I’ve also seen a British project underway and an Australian one in the pipeline as well. There is also uBiome that was crowdfunded on Indiegogo. For about $100, you can find out what is really happing inside your body. But beware. As Tina Hesman Saey from sciencenews.org found out, different labs can come up with widely varying results. Scientists are still working on ways to standardize microbiome findings from varying labs, so don’t panic if your results aren’t what you expect. As long as your samples stay roughly within the average, you’re probably good to go.

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