Wikipedia
Aquificae
The Aquificae phylum is a diverse collection of bacteria that live in harsh environmental settings. They have been found in springs, pools, and oceans. Members of the genus Aquifex, for example, are productive in water between 105 and 138 °C. They are autotrophs, and are the primary carbon fixers in these environments. They are true bacteria ( domain bacteria) as opposed to the other inhabitants of extreme environments, the Archaea.