Microbiology of Soils
Nitrogen fixation

especially changes nitrogen compounds, mostly amines such as NH2
fix the free nitrogen (N2) by which it should not be usable by plants
changes the free nitrogen (N2) to a form usable by plants
both (a) and (b)

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Microbiology of Soils
Denitrification is

both (a) and (b)
reduction of nitrate (NO3-) to nitrogen gas
changing of atmospheric nitrogen (N2) to nitrogen compounds
reduction of nitrate to organic nitrogen compounds

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Microbiology of Soils
Nitrogen fixation by the microorganisms can be detected by adopting the approach of

cultivating the microorganisms in the presence of nitrogen labeled with isotropic nitrogen
demonstrating growth in a nitrogen free medium
measuring15N2 by mass spectrometer
All of these

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Microbiology of Soils
Nitrogen oxidation (nitrification)refers to the

conversion of ammonium ions into nitrates through the activities of certain bacteria.
sulfur is oxidized to the sulfate form through Thiobacillus bacteria
changing of atmospheric nitrogen (N2) to nitrogen compounds
None of these

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