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Difficulty: MediumNutrient and Biogeochemical Cycles

Following the application of an ammonium-based fertilizer to well-aerated agricultural soil, which soil bacterium carries out the initial oxidation of ammonium ions (NH4+NH_4^+) into nitrite ions (NO2−NO_2^-)?

  1. NitrosomonasAnswer
  2. B
    Nitrobacter
  3. C
    Pseudomonas
  4. D
    Rhizobium

Answer

Nitrosomonas is the organism that oxidizes ammonium ions (NH4+NH_4^+) to nitrite ions (NO2−NO_2^-).
Nitrification is a two-step aerobic process. In the first step, Nitrosomonas bacteria oxidize ammonium ions (NH4+NH_4^+) into nitrite ions (NO2−NO_2^-). This prepares the nitrogen for subsequent oxidation into nitrate (NO3−NO_3^-), which plants readily absorb.

Step-by-Step Solution

1
Identify the chemical transformation described in the stem.
The reaction is the oxidation of ammonium (NH4+NH_4^+) to nitrite (NO2−NO_2^-), which is the first phase of nitrification.
Nitrification occurs in two distinct microbial steps in aerobic soil.
2
Match the specific bacterial genus to the first phase of nitrification.
Chemoautotrophic bacteria belonging to the genus Nitrosomonas oxidize ammonium into nitrite.
Nitrosomonas handles the ammonium-to-nitrite step, whereas Nitrobacter oxidizes nitrite to nitrate.

Key Concept

Nitrification (First Stage Bacterial Roles)
Estimated Time:50s
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Topics

Nutrient and Biogeochemical Cycles

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