4 Ways Tiny Microbes Changed Life on Earth Forever

• How the Earth's Atmosphere Got Oxygen - Among the complications of traveling 3 billion years back in time is the fact that you would immediately suffocate. There wasn't much oxygen, if any, in Earth's atmosphere back then. But about 2.7 or 2.8 billion years ago, cyanobacteria—also known as blue-green algae—began to proliferate for reasons still unclear. Like their descendants today, these cyanobacteria could turn sunlight, water, and carbon dioxide into carbohydrates and oxygen. You might recognize this process as photosynthesis.
• The Worst Mass Extinction in the History of the Earth - Methanosarcina simply acquired two genes from an unrelated bacterium about 250 million years ago. These genes let the microbes feed on a previously untapped food source: a carbon compound called acetate abundant in ocean sediments. Feed and grow they did, all the while releasing vast amounts of methane, a greenhouse gas, that warmed the atmosphere and acidified the oceans. Volcanoes could have still played in a role in spewing out nickel, which is necessary for the chemical reaction that lets microbes make methane gas. The abundance of nickel would have eased along the microbe's runaway growth—and decimation of the rest life on Earth.
• Nitrogen-Fixing Microbes and Our Food - In 1910, the German chemist Fritz Haber invented a process to mimic what microbes had been already doing for millions of years: fix nitrogen from the atmosphere into ammonia. While all life on Earth requires nitrogen, the inert nitrogen gas that makes up 78 percent of the planet's atmosphere is useless to all but some nitrogen-fixing bacteria. The Haber process changed that. With a new source of nitrogen fertilizer, agriculture exploded and the human population more than quadrupled in that time. It's estimated that half of the nitrogen in all our bodies originated with the Haber process.
• What Microbes Mean For Climate Change - Microbes can both absorb or release carbon, depending on their diets, so the direction of their influence is not so clear. But, in aggregate, they are huge players in the carbon cycle. Just the microbes that decompose dead plants in the soil, for example, release 55 billion tons of carbon dioxide a year, which is eight times what humans contribute through fossil fuels and deforestation. And climate change is changing how these microbes function. In the cold Siberian tundra, for instance, there is normally not much microbial activity. In recent years, however, the tundra is releasing more carbon dioxide than it absorbs, which scientists believe is due to rising temperatures allowing more microbes to feed in the tundra and release carbon dioxide. The same could be happening in the oceans.

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