Nitrification is a Two Step Process

1. First Step: Ammonium Oxidation   The microorganisms involved are called the ammonia oxidizers.  Nitrosomonas is the most extensively studied and usually the most numerous in soil.  Nitrosospira is an aquatic nitrifier. •Nitrosomonas •Nitrosospira •Nitrosococcus •Nitrosolobus

Ammonia-Oxidizing Bacteria:

  These organisms are chemoautotrophs, growing with ammonia as the energy and CO2 as the main carbon source.  Species are distributed in a great variety of soils, oceans, brackish environments, rivers, lakes, and sewage disposal systems.

2. Second step: Nitrite Oxidation

  Microorganism involved: Nitrobacter

These bacteria comprise a diverse group of rod, ellipsoidal, spherical, and spiral-shaped cells.  At least one strain of Nitrobacter has been described that can grow by anaerobic respiration (denitrification).

  Nitrite-oxidizing bacteria are found in aerobic, but occasionally also in anaerobic, environments where organic matter is mineralized. They are widely distributed in soils, fresh water, brackish water, seawater, mud layers, sewage disposal systems, and inside stones of historical buildings and rocks. They are also found inside corroded bricks and on concrete surfaces such as in cooling towers and highway-automobile tunnels.