picrophilus picrophilus in taxonomy, picrophilus is an archaean genus of the family picrophilaceae. picrophilus scientific classification domain: archaea kingdom: euryarchaeota phylum: euryarchaeota class: thermoplasmata order: thermoplasmatales family: picrophilaceae genus: picrophilusschleper et al. 1996 type species picrophilus oshimaeschleper et al. 1996 species p. oshimae p. torridus schematic map of the ppo1 plasmid from the hyperacidophile picrophilus oshimae picrophilus is an extremely acidophilic genus within euryarchaeota. these microbes are the most acidophilic organisms currently known, with the ability to grow at a ph of less than 0.5. they were first isolated from samples taken from acidic hot springs and dry hot soil in hokkaido (japan). they are obligate acidophiles and are unable to maintain their membrane integrity at ph values above 4. while phylogenetically related to other organisms within thermoplasmata, unlike thermoplasma and ferroplasma, picrophilus contains an s-layer cell wall.