Hyperthermophilic archaea are thriving in deep North Sea and Alaskan oil reservoirs

HOT springs and hydrothermal vents harbour hyperthermophilic archaea and bacteria with the highest growth temperatures known1-6. Here we report the discovery of high concentrations of hyperthermophiles in the production fluids from four oil reservoirs about 3,000 metres below the bed of the North Sea and below the permafrost surface of the North Slope of Alaska. Enrichment cultures of sulphidogens grew at 85°C and 102°C, which are similar to in situ reservoir temperatures7,8. Some species were identical to those from submarine hot vents and may have entered the reservoirs in injected sea water. Several enrichments grew anaerobically in sterilized artificial sea water with crude oil as the single carbon and energy source. These hyperthermophiles may be part of novel high-temperature communities and could be responsible for in situ bioconversions of crude oil fractions at temperatures previously considered too extreme for biochemical reactions 4,7,9,10.