Which archaeon has been recorded growing at temperatures as high as 122°C?

Methanopyrus kandleri has been recorded growing at temperatures as high as 122°C.

This hyperthermophilic archaeon was isolated from a hydrothermal vent in the Gulf of California, where hot, mineral-rich fluids emerge from the seafloor. It produces methane as part of its metabolism, using hydrogen and carbon dioxide rather than relying on oxygen.

The reported upper growth limit of 122°C was measured under high-pressure laboratory conditions that approximate its deep-sea environment. Pressure matters because it helps water remain liquid above its normal boiling point and supports the stability of cellular systems.

Methanopyrus kandleri is not a bacterium, although it is a prokaryote and can resemble bacteria under a microscope. Archaea form a separate domain of life. Another hyperthermophile, Pyrolobus fumarii, is often cited as the first organism found growing above 100°C, but Methanopyrus kandleri holds the better-known 122°C growth record.