Not all life forms need oxygen to “breathe.” In soils, water acts as a barrier to oxygen. Many waterlogged soils contain little or no oxygen as a gas. When there’s relatively little breathable oxygen, various microorganisms use forms of iron, sulfur, nitrogen, or carbon instead. Geobacter uses the rusty-red-colored iron in soils. Microorganisms change the color and chemistry of soils as they respire.
Got pollution? Call in the clean-up crew. Some kinds of microorganisms that live in wet soils and sediments can respire toxic pollutants. As these microbes add electrons to PCBs, arsenic, and uranium, they transform them to less harmful chemicals. Scientists want to harness microbes with these special talents to clean up toxic waste.