Archaebacteria are able to tolerate high temperature as
well as high acidity.
These bacteria are chemoautotrophic which obtain
energy for synthesis of food by oxidising sulphur. Under
anaerobic conditions they oxidise sulphur to sulphuric
acid.

Thermoacidophiles are able to tolerate high
temperature as well as acidity, due to the presence of
(i) branched chain lipids in the cell membranes.
(ii) special resistant enzymes capable of operating under
aerobic conditions.