After making a list of known habitats for bacteria, the group searched scientific literature for direct measurements of cell numbers and the amount of carbon in cells from these habitats. They found that the great majority of bacteria are in sea water, soil, and oceanic and soil subsurface. 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. Another important step was to estimate the carbon content in each bacteria. Knowing the amount of carbon present helps determine carbon cycles.
Scientists assume that carbon in bacteria takes up about one-half of their dry weight.
The scientists were surprised to find that the total amount of carbon of bacteria is nearly equal to the total amount of carbon found in plants. 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. The study could open new areas of inquiry, especially about the rate of mutations and how bacteria behave. The numbers also illustrate that phenomena which are rare in the laboratory can occur frequently in nature.