These almost incomprehensible numbers give only a sketch of the vast pervasiveness of bacteria in the natural world. Because they are so diverse and important, we thought it made sense to get a picture of their magnitude. The study was published in June in the Proceedings of the National Academy of Sciences and was funded in part by grants from the National Science Foundation and the U. S. Department of Energy. Co-authors of the paper from the University of Georgia were David Coleman of the Institute of Ecology and William Wiebe from the Department of Marine Sciences. When people think of bacteria, they likely first consider the nasty ones that cause disease.
Researchers now say that by far the greatest numbers are in the subsurface, soil and oceans.
Scientists have found these cells 40 miles high in the atmosphere and beneath the ocean floor as far down as seven miles deep. In order to estimate the total number of bacteria on Earth, the Georgia researchers divided the Earth into several areas, including oceanic and other aquatic environments, the soil, and the subsurface of soil. Other areas included other habitats such as the air, the insides of animals, and the surface of leaves. The study brought some surprises. 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.