Chemosynthetic bacteria oxides various inorganic substances such as nitrates, nitrites, and ammonia and use the released energy for their ATP production. They play a very important role in recycling nutrients like nitrogen, phosphorus iron and sulphur. These bacteria do not possess photosynthetic pigments. They obtain carbon from organic compounds made by other organisms. They include nitrifying bacteria (Nitrosomes, Nitrobacter), iron bacteria (Ferrobacillus, Leptothrix), hydrogen bacteria, i.e., methanogens (Hydrogenomonas) sulphur bacteria (Thiobacillus, Beggiatoa) and carbon monoxide bacteria (Carboxydomonas).