noun, plural: nitrifying bacteria
Nitrifying bacteria are microbes that are capable of converting ammonium into nitrate especially through the process of nitrification. Nitrification is a process wherein a nitro group is added to an organic compound. It involves the oxidation of ammonium compounds in dead organic material into nitrates and nitrites by soil bacteria (making nitrogen available to plants). Nitrogen from inorganic is converted to organic by nitrate bacteria, which effectively recycles the substance so that it can be used again by plants via root uptake.
Examples of nitrifying bacteria include species of the genera Nitrosomonas (i.e. Gram-negative short to long rods), Nitrosococcus (i.e. large motile cocci), Nitrobacter (i.e. short rods with membrane system arranged as a polar cap), and Nitrococcus (i.e. large cocci with a membrane system randomly arranged in tubes). They derive their energy through the oxidation of inorganic nitrogen compounds. They have complex internal membrane systems where enzymes such as ammonia monooxygenase (oxidizes ammonia to hydroxylamine) and nitrite oxidoreductase (oxidizes nitrite to nitrate) are employed. Nitrifying bacteria that oxidize ammonia include Nitrosomonas and Nitrosococcus species. Nitrifying bacteria that oxidize nitrite include Nitrobacter and Nitrococcus species.