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 (SO₄^2-) 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)
Radioactivity
Water Molecules
Hydrogen gas
Hydrogen Peroxide
Sulfate
Pyrite

Credit: Nicolle Rager Fuller, National Science Foundation.