Chemoautotrophs are living organisms which are not dependent on photosynthesis like all other living things. All life on Earth, encompassing plant kingdom and animal kingdom is dependent on photosynthesis for survival with the exception of chemoautotrophs.

These unicellular organisms derive energy from chemical reactions; synthesize all necessary organic compounds from carbon dioxide. These organisms use inorganic energy source such as hydrogen sulfide, elemental sulfur, ferrous iron, molecular hydrogen and ammonia for survival.

Known chemoautotrophs include some species of bacteria and Achaea, a kingdom of single-celled organisms that usually live in harsh environments. Some examples of chemoautotrophs include sulfur-oxidizing bacteria found in deep sea thermal vents, nitrogen-fixing bacteria found in soil and iron-oxidizing bacteria found in the lava beds.

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