List of Required Reading For "Prokaryotes: Single-celled Organisms"

Thermophiles at Hydrothermal Vents
The article describes thermophiles, especially those living near hydrothermal vents, and the possibility of similar life on other planets. Note that the article is written for the general public and refers to all prokaryotes as "bacteria", even though most thermophiles are Archeans.

If you want to know more about hydrothermal vents, check out some of the links--this whole website has interesting information.

Fossilized Magnetotactic Bacterium in the Orgueil Meteorite
Read this to see what appear to be bacteria from elsewhere in our solar system. If you want to see more possible fossils from meteorites, follow the link "2004 Microfossils in a meteorite" at bottom of the page.