Very little has been known about the trillions of bacteria and other microorganisms in our bodies. But now, scientists with the Human Microbiome Project have completed the first microbial map of healthy humans. Jeffrey Brown speaks with Dr. Eric Green, director of the National Human Genome Research Institute.
JEFFREY BROWN: It's the sort of thing that might literally make your skin crawl, but it's very much a fact of life. Each of us harbors trillions of bacteria and other microorganisms on and in our bodies.
Another fact, very little has been known about these microbes, what they are, where they are, how they differ on an individual person and from person to person. But now scientists, more than 200 of them involved in a five-year project called the Human Microbiome Project, have completed the first microbial map of healthy human beings. And that could eventually help understand and combat some diseases.
The research has just been published.
Here to tell us about it is Dr. Eric Green, director of the National Human Genome Research Institute, part of the National Institutes of Health, which funded the research.
Welcome to you.
DR. ERIC GREEN, Director, National Human Genome Research Institute: Thank you. Happy to be here.
JEFFREY BROWN: Back up a little so we can understand all this. First of all, what are we talking about? What are these microorganisms?
DR. ERIC GREEN: We're talking about these simple organisms like single-cell bacteria, single-cell yeast, even things like viruses. And then we have communities of these microbes that together make up what we refer to as the microbiome.
JEFFREY BROWN: So they live on and in us, in some sense a part of us, but not?
DR. ERIC GREEN: Yes, we are an organism that consists of about 10 trillion human cells, and then we're outnumbered. There's about 100,000 -- 100 trillion of these microbial, of cells and viruses and so forth.
We're outnumbered about 10-1. And most of the time, we live in harmony, but the reason we chose to study the microbiome in the way we did was to better understand what's there and how might the microbiome change in disease.
JEFFREY BROWN: Now, just one more -- they attach to us throughout our lives from birth, right?
DR. ERIC GREEN: Well, when we're born, we're sterile. And then through passage through the birth canal, for example, we start to collect these microbes, and when we start eating, more microbes, and then before you know it, they outnumber us.
But again, this is a very -- there is an ecosystem that we really exist in, and most of the time, it's a perfectly healthy and happy ecosystem.
JEFFREY BROWN: Well, so, when you refer to mapping in this case, what do you mean?
DR. ERIC GREEN: Really, the better word would be more like taking a census.
(LAUGHTER)
JEFFREY BROWN: You mean of the trillions of...
DR. ERIC GREEN: Of the trillions and trillions.
JEFFREY BROWN: Really?
DR. ERIC GREEN: And the reason why is very important to recognize. We're outnumbered 10-1 in these microbes, 100 trillion of them, and yet less than 10 percent of them have ever been isolated and studied in a research laboratory.
JEFFREY BROWN: Yes. Now, why is that?
DR. ERIC GREEN: Well, because we have not figured out how to replicate the happy home they have in us and on us in a laboratory environment.
So we have been blind to them. And yet we know they're important, but we haven't really had a good inventory or a good census of what's there.
JEFFREY BROWN: When you talk about taking a census, you mean like literally which parts of the body -- what's going on where?
DR. ERIC GREEN: And which critters are there and in what numbers.
JEFFREY BROWN: Now, we knew that there were trillions of them, as you said, but I gather one of the surprises here, we didn't know how different they were from each other and how different they are person to person?
DR. ERIC GREEN: And from site to site, as you point out.
And, in fact, so much of our study...
JEFFREY BROWN: But what does that mean, different, different from site to site?
DR. ERIC GREEN: Well, the composition, in other words, the collection of different microorganisms and the numbers that are present.
And so if you go to even two different parts of your body, whether you're talking about your mouth or you're talking about different parts of your skin, we will have a very different collection of these microbes.
JEFFREY BROWN: And each person has a very different collection of trillions?
DR. ERIC GREEN: And then you go from person -- absolutely. You're going to have a different collection at different sites depending upon who you are, maybe where you live, what environmental exposures you have and so forth.
JEFFREY BROWN: Would I have different from my wife, for example, if I'm living in a similar environment?
DR. ERIC GREEN: You almost for certain would because, of course, your own genetic makeup is different and there's this interplay of your own genetics and then the genetics of all these microbes.
JEFFREY BROWN: All right, now, you have said that most of the time we live in harmony with these microbes. And, in fact, I gather there's even a beneficial quality to them?
DR. ERIC GREEN: Well, of course. We couldn't even digest the food that we eat completely if it wasn't for the health of the microbes that live in our G.I. tract.
And so in fact that's very important. And in fact they protect us from many disorders. But what we wanted to do was to have a better understanding of what is normal, what do all of us carry, what's that inventory of different microbes, so that we would have sort of a foundation of information for then studying different disease processes to see how does the microbiome change with disease.
JEFFREY BROWN: Well, but sometimes -- so most of the time in harmony, but sometimes something goes out of whack.
DR. ERIC GREEN: Exactly.
JEFFREY BROWN: Technical term.
DR. ERIC GREEN: But it does go out of whack. And for so long, we would typically only study those microbes that we could isolate, which was only about 10 percent, and then we would really only study microbes like a bacteria one at a time.
But we now know it's much more complicated than just one bacteria, because there's a whole community of these microbes and they're all interacting with one another. And we needed to understand what that interaction looked like amongst themselves and then with our own selves.
JEFFREY BROWN: Well, do we know why they go out of whack occasionally or what process happens that suddenly something that was benign is no longer?
DR. ERIC GREEN: Well, it certainly could be an environmental exposure. It could be related to a whole host of things, including your own genetic makeup and how that influences the composition of those microbes.
JEFFREY BROWN: So, you're beginning -- so knowing more about them, you begin to know more potential to help with certain kind of diseases. I realize it's a ways off, but what are we talking about that this might help us with?
DR. ERIC GREEN: Well, let me give you a couple examples of what we have learned.
We have learned, for example, from the kinds of research that we're discussing that individuals who are malnourished, the microbiome in their G.I. tract is actually different than of a healthy individual. But what's actually very interesting is if you then go and try to improve the health of those individuals by giving them proper nutrition, sometimes their microbiome doesn't adjust and become normal.
Maybe part of the problem is that we don't just need to give them nutrients. We need to think about giving them by some microbes that would help them get to their full health status again. And yet we were, again, blind to this until we started thinking about that some of the things we need to be dealing with is not just the human cells in our body, but also the microbes that are in our body.
JEFFREY BROWN: How far -- what's next? What's the process here? How far away are you from figuring out specific applications for diseases?
DR. ERIC GREEN: Well, let me also explain that what -- the project that we're reporting this week, the Human Microbiome Project, was really about looking at healthy individuals.
We looked at over 240 healthy individuals and we sampled multiple body sites, and we created basically a reference of all the information about which microbes are there and how present are they in all these individuals and also collected information about those individuals, and making all of that available to scientists around the world to share that data.
Now we have a foundation of what's normal. And now we can go in and start studying individuals with different diseases and different processes and try to see how does the microbiome change. There are hints that there's some very exciting developments to be found. Certain skin diseases, G.I. diseases, like ulcerative colitis, Crohn's disease, there's another example where there are hints that maybe the microbiome either is involved in the disease process or might provide a signature for the state of the disease or recovery from the disease.
JEFFREY BROWN: All right, Dr. Eric Green, thanks so much.