Thermococcales

Thermococcales is an order of archaea within the class Thermococci, phylum Euryarchaeota. Members are hyperthermophiles that inhabit extreme environments, most notably deep-sea hydrothermal vents and hot springs. They are predominantly anaerobic and chemoorganotrophic, with growth at temperatures often exceeding 80°C.

Morphology and physiology vary, but cells are generally coccoid to irregularly shaped. Like other archaea, Thermococcales possess membranes composed of ether-linked lipids and have adaptations that support stability at high temperatures and salinity.

Metabolism centers on the catabolism of organic matter. Most species are chemoorganotrophs that break down proteins and amino acids, using elemental sulfur or sulfur compounds as electron acceptors in some conditions. Many Thermococcales ferment substrates when external electron acceptors are limited, producing gases such as CO2 and H2, and sometimes hydrogen sulfide as a metabolic byproduct.

Ecology and distribution: Thermococcales are primarily associated with marine hydrothermal systems but are also found in terrestrial hot springs and other high-temperature habitats. They are often dominant members of microbial communities in vents, contributing to the turnover of organic matter under extreme conditions.

Biotechnological relevance: Members of Thermococcales have provided enzymes with high-temperature stability that are valuable for research and industrial applications. Notably, the Pyrococcus genus, including Pyrococcus furiosus, yields thermostable DNA polymerases used in molecular biology (for example, Pfu polymerase), illustrating the practical importance of this group. Genera within Thermococcales also include Thermococcus, Pyrococcus, and related lineages.