Module 9: Nitrogen Cycle

• label the intermediates of nitrogen fixation

  A) nitrogen gas

  B) ammonia

  C) nitrites

  D) nitrates

  
• label the steps of the nitrogen cycle

  A) nitrogen fixation

  B) ammonia-oxidizing

  C) nitrite-oxidizing

  D) denitrification

  
• nitrogen fixation: reduction of nitrogen gas (NH2) to ammonia (NH3)
• ammonia is used for cellular nitrogen (assimilation)
• nitrogen fixation only occurs in bacteria and archaea
• what forms nitrogen fixing partnerships?

  plants/bacteria and animals/symbionts
• nitrification: conversion of ammonia to nitrate for respiration
• ammonia-oxidizing bacteria: converts ammonia to nitrites by aerobic respiration, O2 is e- acceptor
• nitrite-oxidizing bacteria: converts nitrite to nitrate, partenered with ammonia-oxidizing bacteria
• denitrification: converts nitrate to nitrogen gas for respiration
• denitrification bacteria are facultative anaerobes, use oxygen or nitrate for terminal e- acceptor
• annamox bacteria removes nitrogen under anaerobic conditions
• how does annamox bacteria use respiration?

  • NO2 e- acceptor
  • NH4+ e- donor