Which of the following bacteria are able to synthesize their food from inorganic raw material with the help of energy derived from oxidation of an inorganic substances ?

The bacteria that are able to synthesize their food from inorganic raw material with the help of energy derived from oxidation of inorganic substances are called chemoautotrophs. Ammonia is first oxidised to nitrite by the bacteria Nitrosomonas and/or Nitrococcus. The nitrite is further oxidised to nitrate with the help of the bacterium Nitrobacter. These steps are called nitrification. These nitrifying bacteria are chemoautotrophs.Nostoc, Anabaena, Chlorobium and Chromatium are photoautotrophs.