Lithotrophic bacteria cannot use, of course, their inorganic energy source as a carbon source for the synthesis of their cells. They choose one of three options:
* Lithoheterotrophs do not have the ability to fix carbon dioxide and must consume additional organic compounds in order to break them apart and use their carbon. Only a few bacteria are fully lithoheterotrophic.
* Lithoautotrophs are able to use carbon dioxide from the air as a carbon source, the same way plants do.
* Mixotrophs will take up and use organic material to complement their carbon dioxide fixation source (mix between autotrophy and heterotrophy). Many lithotrophs are recognized as mixotrophic in regard to their C-metabolism.