It is one of a handful of species in the Aquificota phylum, which are a group of thermophilic bacteria that are found near underwater volcanoes or hot springs.

A. pyrophilus is an aquatic microbe that is typically found near underwater volcanoes, marine hydrothermal vents, and/or hot springs where temperatures are extremely high and pressure can be immense.

[5] Oxygen is limited near these hydrothermal vents and underwater volcanos because of the extremely high temperature and reducing power of volcanic gases like H2S.

A. pyrophilus thrives where the oxic and anoxic zones meet in these environments because of the high availability of hydrogen and thiosulfate.

[6] Aquifex pyrophilus was discovered at Kolbeinsey Ridge, North of Iceland by Robert Huber and Karl Stetter in 1992.

[8] Due to its small genome, its ability to survive in extreme heat, its ability to be resistant toward ultraviolet light and ionizing radiation, and because of phylogenetic analyses of the small-subunit 16S rRNA gene, A. pyrophilus is thought to be one of the oldest species in the bacteria domain.

[11] This slight ambiguity in the placement of Aquificales on the phylogenetic tree leaves room for some more research in this field.