By combining direct measurements of the number of prokaryotic cells in various habitats, we found the total number of cells was much larger than we expected. Soil was divided into forest and non-forest types. The researchers then used detailed direct measurements from two studies representative of these soil types to calculate the total number of soil bacteria. Only nine data sets were available for the subsurface, but Whitman used indirect evidence to complete the picture of subsurface bacteria. Another important step in the study was to estimate the carbon content in each bacteria.
Carbon is a crucial element in numerous natural processes.
Knowing the amount of carbon present contributes substantially to the ability to determine carbon cycles. Scientists assume that carbon in the bacteria that live in soil and subsurface takes up about one-half of their dry weight. The group at Georgia found that the total amount of carbon of bacteria is nearly equal to the total amount of carbon found in plants, a discovery which was very surprising to the researchers. The inclusion of this carbon in global models will greatly increase estimates of the amount of carbon stored in living organisms. The new estimates could also change assumptions about the relative amount in plants of other essential nutrients such as nitrogen and phosphorus.