Free living Cyanobacteria-many fix N in heterocysts (e.g.) Anabaena, Nostoc)
How wetlands work as wastewater treatment systems
Sequential nitrification and denitrification--Operates to turn waste ammonia to nitrogen gas. This is the major way in which wetlands are useful in improving water quality. Analogy to processes in our own wastewater treatment plant.
NO3- -> NO2- -> NO(gas) -> N20(gas) -> N2(gas)
Nitrate reductase catalyzes first and second step.
NO3 can serve as an electron acceptor in respiration in place of 02