BioCoder #8

Chapter 8. Analyze Your Own Microbiome

Richard Sprague

As a long-time software developer, I used to think that the machine architecture of a person is based on human genes, the genetic instructions crafted in our DNA, but over the past 10 years, an explosion in the use of low-cost genetic sequencing has revealed that human DNA makes up only a tiny portion of the DNA in our bodies. In fact, if we put all human hardware into a counting machine, it would find that we are roughly:

• 99% human by weight

• 10% human by cells

• 1% human by DNA

With such a tiny amount of our bodies’ DNA residing in human genes, whose values are fixed at birth, it’s no wonder that getting the DNA in our genome analyzed (e.g., by sending a sample and $99 to 23andme) often turns out to be disappointingly unactionable. With rare exceptions, few of the 23andme results can suggest behavior improvements that you didn’t already know: eat plenty of fruits and vegetables and get some exercise.

The rest of you—the 90% of your cells, the 99% of your DNA—comes from non-human organisms, mostly bacteria, living on and within you. Because bacterial cells are so much smaller than human cells, they live invisibly all over your body: on the skin, in the nose and mouth, inside your intestines. There are so many that collectively they weigh several pounds, about the same as your brain, and they change over time in response to their environment. In fact, this is the most intriguing thing about your microbiome: you can alter ...