Microbes to People: Without Us, You're Nothing

Nowhere is the principle of strength in numbers more apparent than in the collective power of microbes.

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Nowhere is the principle of strength in numbers more apparent than in the collective power of microbes, which include bacteria, viruses, some fungi and even some animals that can only be seen with microscopes.

Although each individual microbe is but an almost weightless, one-celled organism, the collective weight of Earth's 5 million-trillion-trillion microbes accounts for most of the planet's biomass—the total weight of all living things. Even the total number of stars in the universe (7 thousand-billion-billion) pales in comparison to the number of microbes on Earth.

It is no understatement to say that microbes run the world. With their mighty collective muscle, microbes control every ecological process, from the decay of dead plants and animals to the production of oxygen. No corner of Earth escapes the influence of microbes, the oldest living organisms. Since microbes first appeared 3.5 billion years ago, about 1 billion years after Earth formed, they have diversified enough to colonize every ecosystem, from scalding vents at the bottom of the ocean to burning desert sands to polar ice.

Microbes are in the food we eat, the air we breathe and the water we drink. Each liter of sea water contains up to a billion bacteria.

Microbes even inhabit the human body. In fact, every person has more than 10 times as many microbes living on and inside his or her body as they have human cells. Although most frequently associated with disease, our microbial hitchhikers help us much more than they harm us. How? By controlling many of the biological processes that are essential to our survival, including the maintenance of our skin and the digestion of our food. Each person's digestive tract alone harbors about 3 pounds of bacteria.

"If all of Earth's microbes died, so would everything else, including us," says Matt Kane of the National Science Foundation. "But if everything else died, microbes would do just fine." Therefore, Kane concludes, "we need microbes more than they need us."

Despite the importance of microbes, scientists have been able to study less than 1 percent of the estimated millions of microbial species that live on Earth. Why so few? Because microbes have strict nutritional requirements and interact with one another in complex ways that currently make it impossible to grow the overwhelming majority of them in the laboratory.

Nevertheless, scientists are rapidly advancing our understanding of microbes through the new science of metagenomics, which involves analyzing the DNA content of entire microbial communities rather than analyzing the DNA of individual microbes, as done in laboratory studies. This new science is finally helping scientists explain what microbial communities do and how they live in their natural habitats.

—Lily Whiteman/NSF

This report is provided by the National Science Foundation, an independent federal agency that supports fundamental research and education across all fields of science and engineering, in partnership with U.S. News and World Report.

Read more about microbes:  Microbes Warn of Ecological Damage