Acidophiles or acidophilic organisms are those that thrive under highly acidic conditions (usually at pH 5.0 or below[1]). These organisms can be found in different branches of the tree of life, including Archaea, Bacteria,[2] and Eukarya.


A list of these organisms includes:




Mechanisms of adaptation to acidic environmentsEdit

Most acidophile organisms have evolved extremely efficient mechanisms to pump protons out of the intracellular space in order to keep the cytoplasm at or near neutral pH. Therefore, intracellular proteins do not need to develop acid stability through evolution. 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.

Studies of proteins adapted to low pH have revealed a few general mechanisms by which proteins can achieve acid stability. In most acid stable proteins (such as pepsin and the soxF protein from Sulfolobus acidocaldarius), there is an overabundance of acidic residues which minimizes low pH destabilization induced by a buildup of positive charge. 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. In this case of kinetic acid stability, protein longevity is accomplished across a wide range of pH, both acidic and basic.

See alsoEdit


  1. ^ Jin, Qusheng; Kirk, Matthew F. (2018-05-01). "pH as a Primary Control in Environmental Microbiology: 1. Thermodynamic Perspective". Frontiers in Environmental Science. 6: 21. doi:10.3389/fenvs.2018.00021. ISSN 2296-665X.
  2. ^ Becker, A., Types of Bacteria Living in Acidic pH". Retrieved 10 May 2017.
  3. ^ a b c Dworkin M, Falkow S (2006). The Prokaryotes: A handbook on the biology of bacteria.
  4. ^ Singh OV (2012). Extremophiles: Sustainable Resources and Biotechnological Implications. John Wiley & Sons. pp. 76–79. ISBN 978-1-118-10300-5.
  5. ^ Quaiser, Achim; Ochsenreiter, Torsten; Lanz, Christa; Schuster, Stephan C.; Treusch, Alexander H.; Eck, Jürgen; Schleper, Christa (27 August 2003). "Acidobacteria form a coherent but highly diverse group within the bacterial domain: evidence from environmental genomics". Molecular Microbiology. 50 (2): 563–575. doi:10.1046/j.1365-2958.2003.03707.x. PMID 14617179. S2CID 25162803.
  6. ^ Pettipher GL; Osmundson ME; Murphy JM (March 1997). "Methods for the detection and enumeration of Alicyclobacillus acidoterrestris and investigation of growth and production of taint in fruit juice and fruit juice-containing drinks". Letters in Applied Microbiology. 24 (3): 185–189. doi:10.1046/j.1472-765X.1997.00373.x. PMID 9080697. S2CID 6976998.
  7. ^ a b c Rawlings, Douglas; Johnson, D. Barrie. "Eukaryotic Acidophiles". Encyclopedia of Life Support System (EOLSS). Eolss Publishers. Archived from the original on 2014-10-13. Retrieved 3 February 2014.
  8. ^ Menzel, U.; Gottschalk, G. (1985). "The internal pH of Acetobacterium wieringae and Acetobacter aceti during growth and production of acetic acid". Arch Microbiol. 143 (1): 47–51. doi:10.1007/BF00414767. S2CID 6477488.

Further readingEdit