Thermoplasmata is a class of archaeans in the phylum Thermoplasmatota.

All are acidophiles, growing optimally at pH below 2. Picrophilus is currently the most acidophilic of all known organisms growing at a minimum pH of 0.06. Many of these organisms do not contain a cell wall, although this is not true in the case of Picrophilus. Most members of Thermoplasmata are thermophilic.

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