Nitrite Oxidising Bacteria - Four genera have been recognized in nitrite oxidising bacteria. They are Nitrobacter, Nitrococcus, Nitrospina and Nitrospira which occupy strictly aerobic habitats. Among these genera Nitrobacter is the important one, with a single species Nitrobacter winogradskyi.
They are Gram-negative rods which reproduce by budding. Nitrosococcus contains a single species Nitrococcus mobilis and Nitrospina also includes a single species Nitrospina gracilis. Nitrospira marina is the only member of the newly recognized genus Nitrospira.
