By Oyang Teng, Biological Sciences ’14

Microbes are the planetary engineers of the biogeochemical cycles that sustain all life on earth. At the molecular scale, the biological turnover of such key elements as hydrogen, carbon, oxygen, nitrogen, iron and sulfur depends on the enzymatic transfer of electrons from reduced (electron-donating) to oxidized (electron-accepting) forms of these elements. On the global scale and over geological time, reduced substrates and oxidized products map to a vast, often circuitous flux between the interior depths of the mantle and the oceans, land, and atmosphere.

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