Aquifex

Aquifex is a genus of bacteria, one of the few in the phylum Aquificae. The two species generally classified in Aquifex are A. pyrophilus and A. aeolicus. Both are highly thermophilic, growing best in water temperature of 85 °C to 95 °C. They are true bacteria (also known as the domain Eubacteria) as opposed to the other inhabitants of extreme environments, the Archaea.

Both species of Aquifex are rod-shaped bacteria with a length of 2 to 6 µm and a diameter of around 0.5 µm. They are non-sporeforming, Gram negative autotrophs. Aquifex means water-maker in Latin, and refers to the fact that its method of respiration creates water. Aquifex tend to form cell aggregates composed of up to 100 individual cells.

Aquifex are thermophilic and often grow near underwater volcanoes or hot springs. A. aeolicus requires oxygen to survive, but can grow in levels of oxygen as low as 7.5 ppm. A. pyrophilus can even grow anaerobically by reducing nitrogen instead of oxygen. Like other thermophilic bacteria, Aquifex has important uses in industrial processes.

The genome of A. aeolicus has been successfully mapped. , This was made easier by the fact that the length of the genome is only about a third of the length of the genome for E. coli. Comparison of the A. aeolicus genome to other organisms showed that around 16% of its genes originated from the Archaea domain. Members of this genus are thought to be some of the earliest members of the eubacteria domain.

A. aeolicus was discovered north of Sicily, while A. pyrophilus was first found just north of Iceland.