What is the microbiome?

Dr. Andrea Azcarate-Peril is director of the Microbiome Core Facility, one of more than 60 such facilities supported by the N.C. Translational and Clinical Sciences Institute at the UNC School of Medicine in Chapel Hill. Here she talks about how bacteria are a part of life, one that it is practically impossible to live without. Questions and answers have been edited.

Q: I've heard this term "microbiome" thrown around, much like genome or proteome. What is it exactly?

The term was coined by a very accomplished scientist named Joshua Lederberg, and he defined microbiome as a "menagerie of microbes." Basically he said the human body is composed of three parts. You have the human cells with all their DNA, then you have the mitochondria (the energy-producing factories of the cells) with their DNA, and then you have the microbiome, which is all the bacteria in our bodies and their DNA. It has become really relevant because very recently we have developed the tools to study these bacteria.

Q: Why has it been so difficult to study many of these types of bacteria?

Before we relied on culturing techniques to detect them, and we know now that 70 percent to 80 percent of our bacteria do not grow very well in the lab. The main reason is probably because these bacteria need other bacteria, so they need the community. Also, many of them are anaerobic, meaning they like to grow in the absence of oxygen.

So with new culture-independent techniques like DNA sequencing, we are now able to detect that we have millions of bacteria that we didn't know we had before.

For example, we did a study in human breast milk, one source that we thought didn't contain any bacteria. Turns out, breast milk contains lots of good bacteria, which moms are passing on to their babies to help colonize their guts.

Where else? We have bacteria everywhere; we have it on our skin, in our mouths. You probably heard that we have more bacterial cells in our bodies than human cells.

Q: So why do we have these bacteria and how do they affect human health?

The issue is symbiosis. Bacteria have a lot of enzymes we don't have - that we don't need to have - that help us digest specific foods. When the balance in our gut gets disturbed we go from having helpful bugs to pathogenic bugs that produce toxins and can give us diarrhea and other nasty symptoms.

Q: So do you eat yogurt to get your own dose of healthy bacteria or probiotics every day?

Of course. I have been working with probiotics for 16 years, and when you learn what bacteria can do for you, you eat yogurt every day.

What I am interested in now is the fact that every person is different. Since we have different bacteria, it makes sense that some strains of bacteria might work for you but not for other people. It has never been truer that we are what we eat.