Thermoplasmatales

In taxonomy, the Thermoplasmatales are an order of the Thermoplasmata. All are acidophiles, growing optimally at pH below 2. Picrophilus is currently the most acidophilic of all known organisms, being capable of growing at a 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 the Thermotoplasmata are thermophilic.

Phylogeny
The currently accepted taxonomy is based on the List of Prokaryotic names with Standing in Nomenclature (LPSN) and National Center for Biotechnology Information (NCBI).