<figcaption> Credit: Jeremy Burgess / Photo Researchers, Inc</figcaption>
Credit: Jeremy Burgess / Photo Researchers, Inc

The paper:
J. Gans et al., "Computational improvements reveal great bacterial diversity and high metal toxicity in soil," Science, 309:1387-90, 2005. (Cited in 72 papers)

The finding:
John Dunbar and colleagues at Los Alamos National Laboratory developed a statistical technique to more accurately estimate the diversity of bacteria found in soil. Their reanalysis of historical data extended the upper limit of bacterial diversity from 10,000 (the established benchmark) to upwards of 8,000,000 species per gram of soil.

The significance:
The findings were a drastic shift from the benchmark (Appl Environ Microbiol, 56:782-7, 1990), but Dunbar's team provided only a statistical model for soil bacteria diversity, not a direct measurement. His findings sparked debate among soil biologists about how complex soil bacterial communities really are, says Noah Fierer, microbial ecologist at the University of Colorado.

The controversy:
Recently, Eric Triplett at...

The numbers:

Bacteria species per gram of typical soil
10,000 The old benchmark for soil bacteria diversity
25,000 - 50,000 From pyrosquencing
1,000,000 - 8,000,000 From Gans et al. estimates

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