Microbes are everywhere—even inside us. But because so many of these bugs won't grow in the lab, scientists have had a tough time figuring out just who they are and how they live. That may soon change. By sequencing the DNA in individual cells, researchers have gotten to know 200 new microbes—and they may be able to characterize many more. The more researchers are able to fill out the microbial tree of life, the better able they will be to understand the role that microbes play in the environment and to harness microbial proteins for practical applications.
The approach "steps off into a whole world that up to now has been pretty inaccessible," says Norman Pace, a microbiologist at the University of Colorado, Boulder, who was not involved with the work. "It's a world we knew was there but we couldn't get to it."
Almost 400 years ago, the microscope opened a new vista on invisible life. Yet only in the 20th century did researchers become aware of how diverse the microbial world is. At that time, molecular biology made it possible for researchers to compare the same piece of DNA in a variety of organisms. That DNA, which coded for a piece of the ribosome, the cell's protein-producing factory, revealed vast differences in microbes and led researchers to divide them into two groups, bacteria and archaea, which includes organisms that live in extreme environments such as hot springs. Once researchers began sampling this piece of DNA from many different environments, they were shocked by just how many kinds of microbes existed. It seems that every time researchers test samples from the soil, the ocean, or even the bodies of organisms, they detect dozens if not hundreds of unknown microbes.