The Nitrogen cycle

Organically available nitrogen

NH4

nitrogen fixation

N2 to NH4, costs 16 ATP per an N2

nitrogenase

nitrogen fixing enzyme very O2 sensitive

nitrification

NH4 to NO3, sequential reactions produce, uses O2 terminal electron receptor

nitrosomonas

NH4 to NO2

nitrobacter

NO2 to NO3

ammonium monoxygenase

enzyme that catalyzes NH4 to NO2 production

nitrite oxidoreductase

An enzyme that catalyzes NO2 to NO3 production

Annamox (anaerobic ammonium oxidation)

Tied to autotrophs, oxidizes NH3 using nitrate as TeA produces N2

annamoxosome

organelle in annamox bacteria that protect from toxic hydrazine intermediate

ammonification

decomposition of organic N molecules from amino acids and proteins, some oxidize ammonium they produce for more E and electrons

ammonium assimilation

the process by which plants and microorganisms take up ammonium from the soil to incorporate it into organic molecules

GS/GOGAT enzymes/glutamate dehydrogenase

ammonium assimilation enzymes

assimilatory nitrate reduction to ammonium

Nitrate to biomass, nitrate is reduced to ammonium then incorporated

glutamine synthetase

GS/GOGAT system uses energy, high ammonium affinity common in low nitrogen environments

glutamate dehydrogenase

requires electrons, lower ammonium affinity common in nitrogen rich environmentsIt is an enzyme that catalyzes the reversible conversion of alpha-ketoglutarate and ammonium to glutamate, playing a crucial role in amino acid metabolism.

denitrification

4 reductions from NO2 to NO to N2O to N2, nitrogen lost from habitat

dissimilatory nitrate reduction to ammonium (DNRA)

NO2 to NH4 under anaerobic conditions uses NO2/NO3 as TeA

incomplete denitrification

makes N2O greenhouse gas when the microbe abandons the dentirication process because of O2, pH is to low, or nitrate is obtained

Nitrifier dentirification

heterotrophic nitrifiers use nitrate as an electron acceptor to produce N2O under aerobic conditions

Nitrogen and eutrophication

limiting nutrient for growth often so when there is to much N all the oxygen gets used up then everything dies

agriculture and nitrous oxide

fertilizer and incomplete dentirification release N2O