Most life on earth is fueled directly or indirectly by sunlight. There are, however, certain groups of bacteria, referred to as chemosynthetic autotrophs, that are fueled not by the sun but by the oxidation of simple inorganic chemicals, such as sulfates or ammonia.
Chemosynthetic autotrophs are a necessary part of the nitrogen cycle .
Some groups of these bacteria are well suited to conditions that would have existed on the earth billions of years ago, leading some to postulate that these are living representatives of the earliest life on earth. In these ecosystems, the primary producers in the food web are bacteria whose life functions are fueled by inorganic chemicals that seep up from the earth's crust. See also autotroph . Click here to see documents from Electric Library, a pay service. Listing from Electric Library , a pay service.