SME
Ecology · Problem type
Microbes of the nitrogen cycle
Use this for “Which microbes turn ammonium into nitrate, and which return nitrogen to the air?”
Explore
N₂ is fixed to ammonium, oxidized to nitrate, built into organisms, released as ammonium when they decay, and returned to the air as N₂.
Assumptions
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Nitrogen limits growth in most ecosystems: N₂ fills the air, but only a few prokaryotes can break its triple bond.
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Each step changes nitrogen’s oxidation state, from −3 in NH₄⁺ to +5 in NO₃⁻, and the microbes doing it gain energy or nitrogen.
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Nitrification needs oxygen; denitrification runs where oxygen is scarce, in waterlogged soil and sediments.
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