Pyrolobus

Pyrolobus is a genus of archaea in the family Pyrodictiaceae, within the order Desulfurococcales. Members of this genus are hyperthermophiles, known for thriving in extremely hot environments such as hydrothermal vents. The best-known and first-described species is Pyrolobus fumarii, the type species of the genus.

Discovery and habitat

Pyrolobus fumarii was isolated from a black-smoker hydrothermal vent chimney in the TAG field along the Mid-Atlantic Ridge, at depths of several kilometers. This lineage has since been associated with other hydrothermal vent ecosystems, where temperatures and conditions exceed those tolerated by most organisms. The extreme heat and high-pressure conditions of these habitats drive many of the unique metabolic adaptations observed in Pyrolobus species.

Physiology and metabolism

Pyrolobus species are anaerobic and highly thermophilic or hyperthermophilic. They grow best at temperatures around 105°C and can tolerate a temperature range extending into the high 90s to over 110°C. Metabolically, they are chemolithoautotrophs that obtain energy by oxidizing hydrogen and use carbon dioxide as their carbon source. Carbon fixation is typically via pathways capable of assimilating CO2 under extreme conditions, such as the reductive acetyl-CoA (Wood–Ljungdahl) pathway. Oxygen is not used by these organisms, reflecting their adaptation to anoxic vent environments.

Ecology and significance

As components of deep-sea hydrothermal vent communities, Pyrolobus species contribute to primary production under conditions lethal to most life forms. Their existence helps illuminate the upper limits of life on Earth and informs models of carbon cycling in extreme ecosystems.

See also

Pyrodictiaceae, Desulfurococcales, hyperthermophiles.