Nitrifying bacteria

Nitrifying bacteria are chemoautotrophic bacteria that grow at the expense of inorganic nitrogen compounds. Many species of nitrifying bacteria have complex internal membrane systems that are the location for key enzymes in nitrification: ammonia monooxygenase which oxidizes ammonia to hydroxylamine, and nitrite oxidoreductase, which oxidizes nitrite to nitrate.

Ecology
Nitrifying bacteria are widespread in soil and water, and are found in highest numbers where considerable amounts of ammonia are present (areas with extensive protein decomposition, and sewage treatment plants). Nitrifying bacteria thrive in lakes and streams high imputs of sewage and wastewater because of the high ammonia content.

Oxidation of ammonia to nitrate
Nitrification in nature is the result of actions of two groups of organisms, the nitrosifyers (ammonia-oxidizing bacteria) and nitrifying bacteria (nitrite-oxidizing, nitrate producing bacteria)

Nitrosifying bacteria

1. NH3 + O2 + 2e- + 2H+ → NH2OH + H2O

2. NH2OH + H2O + 1/2 O2 → NO2- +2 H2O + H+

Nitrifying bacteria

NO2- + 1/2 O2 → NO3-
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