The Next Human Genome Project: Our Microbes

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Recent research from Gordon's lab hints at the potential public-health impact of a clearer understanding of our microbial tenants. Gordon and his colleagues have shown that obese people harbor different microbial communities than lean people. And as obese people lost weight, their microbes began to look more like their lean counterparts' microbes.

Researchers aren't yet sure what triggers the differences, but they found in a similar study in mice that the microbial populations of obese mice could more effectively release calories from food during digestion than could microbes of their lean littermates.

While exciting, Gordon's research also illustrates the challenges of cataloging microbes. To truly interpret the human microbiome, scientists will need to look at the variation in microbial communities among many people and a variety of populations. Complicating the problem is that, while an individual's human genome is static, a person's microbial composition--and thus his or her microbiome--fluctuates over time. So an accurate picture of one person's microbiome could require multiple resequencing efforts.

These types of studies could yield the biggest reward, revealing whether different organisms are correlated with different health states. Gordon and others hope that a microbial analysis will ultimately become a routine part of medical exams, perhaps used to diagnose different diseases.

Scientists are still debating whether the microbiome will become a road-map project, and if so, what the final goals of the project will be: should they focus on generating complete sequences of dominant microbes, for example, or devote equal energy to the complex task of studying microbial variation?

In the meantime, microbiologists are getting ready. Three large sequencing centers--at Baylor, the Broad Institute, and Washington University--have garnered funding to sequence the genomes of a few of the gut microorganisms that can be grown in the lab, which will be crucial in later studies. Ultimately, says Gordon, "we'll get a much more transcendent view of ourselves as a supraorganism with traits acquired from our microbial partnerships."