Nitrogen cycle

N fixation

nitrogenase, free living or symbiotic

Rhizobium, klebsiella

nitrogen fixers examples

assimilatory nitrate reduction

For growth NO3 → NO2 then NO2 → NH4 which gets incorperated

nitrate reductase

NO3 → NO2

nitrite reductase

NO2 → NH4

assimilatory nitrate reduction inhibiton

end product inhibition by NH4+

dissimilatory nitrate reduction

anaerobic respiration, NO3 → NO2, facultative anaerobes use as TeA, many produce N2 or N2O by dentirification

annamox

a process that converts NO2 and NH4+ into N2 gas under anoxic conditions

dissimilatory nitrate reduction to ammonia

polluted water with NO3, aerobic and anaerobic conditiosn

ammonium assimilation

GS-GOGAT system (glutamine synthetase), very nitrate sensitive (low nitrate conditions)

glutamine oxoglutarate aminotransferase

an enzyme involved in the conversion of glutamate and 2-oxoglutarate to glutamine and aspartate in nitrogen metabolism.

nitrificaiton

soil, wastewater, deep ocean, bacteria or archaea take organics/NH4 and convert to NO3

ammonium oxidation

ammonium monooxygenase converts NH4 to NO2

nitrosomonas and nitrococcus

ammonium oxidizer examples

nitrite oxidation

nitrite oxidoreductase converts NO2 to NO3

nitrospira and nitrobacter

nitrite oxidizers examples

coannamox

complete NH4 oxidation by one species (NH4 to NO3), biofilms with low O2 and low NH4

denitrification

anaerobic NO3 → N2 or N2O

paracoccus dentirificans and thiobacillus dentirifcans

examples of denitrifiers

annamox

NH4 and NO2 to N2, oxidation of NH4

Planctomycetes

example of annamox bacteria