Two hundred trillion microscopic organisms -- bacteria, viruses, and fungi -- are swarming inside of you right now. The largest collection, weighing as much as four pounds in total, clings to your gut. Collectively, it's called the 'human microbiome' -- and in a healthy individual, they are in symbiosis with their host (you) and usually manage to even protect you from the 'not good' microbes. There are 20 times as many of these microbes as there are cells in the body, and each of us hosts at least 1,000 different species. Seen through the prism of the microbiome, a person is not so much an
individual human body as a super-organism made up of diverse ecosystems.
In-depth analysis of the human body’s microflora has been possible only in the past few years—a by-product of the same new gene sequencing techniques that have allowed scientists to cheaply and accurately identify the DNA of the human genome. Gene sequencing has opened a huge door to how complex these communities are.
Like a lush rain forest, a healthy microbiome in the human gut is a diverse ecosystem that thrives only when all the interdependent species are healthy too. In an ecological sense, more diverse communities are healthy. No one species is dominant, and the ecosystem is more productive and resistant to major changes. Imbalances in the microbiome might very well be linked to diseases such as diabetes, allergies, and obesity.