These organisms can be found in different branches of the tree of life, including Archaea, Bacteria,[2] and Eukarya.
However, other acidophiles, such as Acetobacter aceti, have an acidified cytoplasm which forces nearly all proteins in the genome to evolve acid stability.
[8] For this reason, Acetobacter aceti has become a valuable resource for understanding the mechanisms by which proteins can attain acid stability.
Other mechanisms include minimization of solvent accessibility of acidic residues or binding of metal cofactors.
In a specialized case of acid stability, the NAPase protein from Nocardiopsis alba was shown to have relocated acid-sensitive salt bridges away from regions that play an important role in the unfolding process.