Diversity of Archaea IV

Hyperthermophilic archaea thrive above 80°C and inhabit hydrothermal vents or volcanic soils where temperatures exceed the boiling point of water.

Methanopyrus kandleri survives up to 122°C, the highest known temperature for microbial life, beyond which proteins, membranes, and DNA degrade.

Hyperthermophilic archaea have many features that prevent cell denaturation and reinforce their structural and functional stability at high temperatures.

Hyperthermophiles possess a heat-resistant monolayer cell membrane made of biphytanyl tetraether lipids.

Specialized enzymes, called thermozymes, remain functional at high temperatures due to stronger ionic interactions, tightly packed hydrophobic cores, and salt bridges.

Unique chaperones called thermosomes stabilize protein folding and refold denatured proteins.

Reverse DNA gyrase, unique to hyperthermophiles, introduces positive supercoils, while histone-like proteins compact DNA for stabilization. Potassium solutes stabilize DNA and guard against thermal denaturation.

rRNAs of hyperthermophiles have up to 15% higher GC content, providing ribosome stability through stronger hydrogen bonding.