KCET 2014 Biology Solved Paper

The conversion of ammonia into nitrite (NO2−) is done by bacteria of the genera Nitrosomonas or Nitrococcus. Nitrite is further oxidized to nitrate by members of the genus Nitrobacter. These two steps sum up the process called nitrification and the bacteria are called nitrifying bacteria. These nitrifying bacteria act as chemoautotrophs, that is, energy is obtained by oxidizing inorganic substances such as ammonium or nitrite is used to convert carbon dioxide to organic carbon.