Alkaliphiles

Alkaliphiles

Alkaliphiles

Alkaliphiles are extremophile microorganisms found in alkaline environments. Alkaliphiles grow in a pH range of 7.5 to 14.
Example : Thermococcus alcaliphilus.

Alkaliphiles maintain an internal pH near neutrality by changing the pH of their habitats producing acidic or basic products.

Haloalkaliphiles are mainly found in extremely alkaline saline environments, such as in the Western soda lakes of United States and the Rift Valley lakes of East Africa.
For example, Bacillus halodurans, Bacillus firmus.

Enzymes from alkaliphiles are nowadays used with detergents softening the fabric.

Alkaliphiles maintain cytosolic acidification through both passive and active means:

Passive acidification

Cell walls of alkaliphiles contain acidic polymers composed of galactouronic acid, glutamic acid, gluconic acid, aspartic acid and phosphoric acid.

These residues form an acidic matrix and that helps protect the cell from alkaline conditions by preventing the entry of hydroxide ions and allowing for the uptake of  Na⁺  and H₃O⁺   ions.

The peptidoglycan of  Bacillus subtilis contain higher levels of hexosamines and amino acids as compared to its neutrophilic part.

Active acidification

This is characterised by Na⁺ / H⁺ antiporters.

‌Hydrogen ions are first extruded through the electron transport chain. This proton extrusion establishes a proton gradient that drives electrogenic antiports, which drive sodium ions out of the cell in exchange of hydrogen ions. This leads to the net accumulation of internal protons. This protons lead to a lowering of cytosolic pH.

Na⁺ / H⁺ antiports are required for alkaliphilic growth, whereas K⁺/ H⁺ antiporters  or  Na⁺ / H⁺ antiporters can be utilised by neutrophilic bacteria.

Alkaliphiles

Written By

Sadia Akhtar
Student of Department of Microbiology
Jagannath University.
Email- sadiabd810@yahoo.com