(Inside Science) -- A single soil sample can contain hundreds to thousands of different kinds of bacteria, most of them never described in detail. But a new study takes a major step in sifting through this diversity, identifying a few hundred types that are especially abundant and widespread.
The researchers analyzed soil from 237 sites across six continents, representing ecosystems from arid grasslands to tropical forests. Using genetic data from cellular structures called ribosomes, they categorized bacteria by "phylotype" -- a grouping level similar to "species," but easier to define in bacteria.
Together, the samples contained more than 25,000 different phylotypes of bacteria. Most of these phylotypes were rare and found only in specific locations, but 511 were abundant in a wide range of soils. These phylotypes made up only 2 percent of the total diversity, but they appeared to account for about 41 percent of bacterial cells in the world's soils.
The study narrows the immense number of bacterial types "to a 'most wanted' list," wrote the researchers in a study published today in the journal Science. According to the authors, future research into the genetics and ecology of these dominant bacteria could help clarify how soils function in ecosystems. Eventually, researchers may even be able to predict how bacterial communities will respond to changes in climate and land use.