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X-treme Microbes — Text-only | Flash Special Report
Radiation Eaters

How to Eat Radiation
The newly discovered microbes were found nearly two miles deep in ancient water seeping through a fracture in a 2.7 million-year-old rock formation. The rock contains radioactive uranium, thorium and potassium, as well as an iron-sulfur compound called pyrite, or fool’s gold, among other constituents.

A cascade of reactions supplies the microbes with their remarkable if meager diet. First, radioactivity cracks water molecules (H2O) into their components: hydrogen (H2) and oxygen (O).

The detached oxygen atoms combine with adjacent water molecules to make hydrogen peroxide (H2O2). The peroxide then reacts with an iron-sulfur compound called pyrite (FeS2), producing sulfate ions (SO42-) that the microbes can “eat.” Each sulfate ion is lacking two electrons, which are supplied—inside  the organisms—by the conveniently available leftover hydrogen gas (H2). The microbes use that reaction to store energy.

Legend (for animated Illustration)
Water Molecules
Hydrogen gas
Hydrogen Peroxide

Credit: Nicolle Rager Fuller, National Science Foundation.