hydrothermal vents

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…by the vents on the sea floor. The bacteria take the sulfur in the hydrogen sulfide and oxidize it producing energy. H2 + S ---> H2S + energy. This energy drives all life forms in the deep sea vents, producing sugars, fats, and amino acids in living forms very much as plants do, but based on sulfur. Like photosynthesis this process is highly complex, but it sustains a huge number of organisms in the sea (Stover).