Global Nitrogen Cycle 1012g Ny

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Global Nitrogen Cycle (1012g N/y)
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NO3
Microbial Nitrogen Cycle
NO2
NO
denitrification
nitrification
N2O
assimilation
N2
nitrogen fixation
NH4
ammonification
Organic N
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New Microbial Nitrogen Cycle
NO3
NO2
NO
Ammonia Oxidizing Archaea (AOA)
Anaerobic Ammonium Oxidation (ANAMMOX)
N2O
N2
NH4
Organic N
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Nitrogen compounds in the nitrogen cycle
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(No Transcript)
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NH3 oxidation
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Nitrification
NH3 ? NO2- ? NO3-
NH3 oxidation
NO2- oxidation
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Nitrifying Bacteria

• Key genera Nitrosomonas, Nitrobacter
• Major metabolisms nitrification
• Habitats sewage treatment, freshwater, marine,
  soil
• Members ammonia oxidizing bacteria, nitrite
  oxidizing bacteria
• AOB
• NH3 oxidation, chemolithotrophic autotrophic
  living
• beta and gamma subgroups
• NOB
• NO2- oxidation, facultative chemolithotrophic
  living
• alpha, gamma, delta subgroups

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Molecular determination of ammonia oxidation
AMO gene
Horz et al., 2004
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Distribution of nitrification rates in the ocean
Ward, 1987
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Discovery of archaeal ammonia oxidation
Treusch et al., 2005
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Ammonia oxidizing archaea

• Nitrosopumilus maritimus
• Chemolithoautotrophic ammonia oxidzer

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Denitrification
NO3- ? NO2- ? NO ? N2O ? N2
Zumft, 1997
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Denitrification in sediments
Sorensen et al., 1978
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Molecular detection of denitrifying bacteria

• NO3- ? NO2- ? NO ? N2O ? N2

nar nir nor nos
Cytochrome cd1 nitrite reductase (nirS) Copper
nitrite reductase (nirK)
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Nitrite reductase gene (nirS) in Chesapeake Bay
sediments
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Anaerobic ammonia oxidation
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ANAMMOX new sink of nitrogen cycle
NH4 NO2- ? N2 2H2O
Anoxic water columns
Marine sediments
Kuypers et al., Nature 422608
Dalsgaard et al., Res. Microbio. 156457
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ANAMMOX Bacteria
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Molecular detection of ANAMMOX bacteria
Schmid et al., 2005
Kirkpatrick et al., 2006
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Measuring ANAMMOX activity 15N IPT

• ANAMMOX NH4 NO2- ? N2
• Denitrification 2NO3- ? 2NO2- ? 2NO ? N2O ? N2

Dalsgaard Thamdrup, 2002, Appl Environ
Microbiol 683802
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Significance of ANAMMOX in N removal
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N2 fixation

• N2 converts to 2NH3.
• N2 16 ATP 8e- 8H ? 2NH3 16 ADP 16 Pi
  H2
• Diverse groups of organisms are able to fix N2
  (Table 17.10).
• Nitrogenase complex
• dinitrogenase dinitrogenase reductase

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N2 fixing cyanobacteria in the ocean
Nitrogen fixation in heterocystous cyanobacteria
(Anabaena)
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Molecular determination of N2 fixation in
seawater (nifH genes)
Paerl and Zehr, 2000
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Nitrogen assimilation
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Molecular determination of NO3- assimilation
nirA gene
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New paradigm in nitrate reduction
NO3- ? NO2- ?NH4
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Enzymes in nitrite ammonification
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Molecular determination of nitrate ammonification
communities
nrfA gene
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Ammonification
DON ? NH4

• Regeneration of NH4 from DON.
• Heterotrophic bacteria
• Aerobic and anaerobic processes
• No energy gain and nitrogen loss

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Microbial nitrogen cycle