They're everywhere. Bacteria are the huddled masses of the microbial world, performing tasks that include everything from causing disease to adding nitrogen to soil.
When people think of bacteria, they likely first consider the nasty ones that cause disease, but the bacteria inside all animals including humans makes up less than one percent of the total. Scientists have found bacteria 40 miles high in the atmosphere and beneath the ocean floor some seven miles deep. But by far the greatest numbers are in subsurface rocks, soil and oceans.
How many are there? For the first time, a team of researchers from the University of Georgia has made a direct estimate of the total number of bacteria on Earth, and the number makes the globe's human population look downright puny. The group, led by microbiologist William B. Whitman, estimates the number to be five million trillion trillion - that's a five with 30 zeros after it.
The Earth weighs 5,972,000,000,000,000,000,000, or 5.9 x 1021 tons. As noted there are 5 x 1030 bacteria, and one grain of rice weighs .0006 ounces. Multiply the number of bacteria by 1/10 the weight of one grain of rice and you get 9.37500 × 1021 tons, much heavier than Earth.PB