I could be mistaken, but I'm actually asking for what these bacteria (e.g., Geobacter) use as a carbon source - that is, where do they get the raw materials to build proteins and DNA? Options are that they reduce CO2 (which could be super cool but surprising for something that lives underground; plants do this in photosynthesis) or that they get their carbon from the environment.
It looks like Geobacter can at least use exogenous acetate[1] but it's not clear what was provided to the lab-grown bacteria described in the article.
The comment that was deleted copied the text from the beginning of the Wikipedia page on Geobacter; I'm pasting it below:
Geobacter... [is capable of oxidizing]... iron, radioactive metals and
petroleum compounds into environmentally benign
carbon dioxide while using iron oxide or other available
metals as electron acceptor.
It looks like Geobacter can at least use exogenous acetate[1] but it's not clear what was provided to the lab-grown bacteria described in the article.
[1] http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1392927/
EDIT:
The comment that was deleted copied the text from the beginning of the Wikipedia page on Geobacter; I'm pasting it below: