Scientists Peek Inside the 'Black Box' of Soil Microbes to Learn Their Secrets

Scientists Peek Inside the 'Black Box' of Soil Microbes to Learn Their Secrets

Microorganisms play a vital role in growing food and sustaining the planet, but they do it anonymously. Scientists haven't identified most soil microbes, but they are learning which are most common.

A tablespoon of soil contains billions of microscopic organisms. Life on Earth, especially the growing of food, depends on these microbes, but scientists don't even have names for most of them, much less a description.

That's changing, slowly, thanks to researchers like Noah Fierer, at the University of Colorado, Boulder. Fierer think microbes have lived in obscurity for too long. "They do a lot of important things for us, directly or indirectly, and I hope they get the respect they deserve," he says.

These microbes create fertile soils, help plants grow, consume and release carbon dioxide, oxygen and other vital elements. But they do it all anonymously. Scientists haven't identified most of these species and don't know much else about them, either, such as "what they're doing in soil, how they're surviving, what they look like," Fierer says.

According to Fierer, they've been extremely difficult to study, in part, because most of them refuse to grow anywhere but in the dirt, "so we can't take them out of soil and study them in the lab."

Some scientists call the community of soil microbes a "black box." You can't see inside.

Fierer and other scientists, however, have come up with new ways to open up that box just a little. They collect samples of soil and extract all the DNA contained in that sample, from all the organisms living there. That's a lot of diversity, even in a small sample. "Thousands of bacterial species can be found in a given teaspoon of soil," Fierer says.

They study the DNA in each sample. They look, specifically, at a particular region of DNA that's common to all living organisms. And by making a catalog of all the different versions of that region, they can tell how many different kinds of microbes live in that sample. They also can tell how common each type of microbe is. There's a huge consortium of scientists, called the Earth Microbiome Project, using this approach to study soil microbes.

Fierer, who's a member of that collaboration, discovered that even though there may be millions of soil microbes, there's a relatively small group that seems to dominate. The microbes show up in large numbers in soil samples from deserts, grassy prairies and forests. Fierer's report appears this week in the journal Science.