Thermoacidophiles: These archaebacteria have dual ability to tolerate high temperature as well as high acidity due to two reasons: branched chain lipids in the cell membranes and presence of special resistant enzyme capable of operating under acidic conditions. They often live in hot sulphur springs where the temperature may be as high as 80 degree C and pH as low as 2.
Basically these archare are chemosynthetic i.e., they obtain energy for synthesis of food from oxidizing sulphur. Under aerobic conditions they usually oxidize sulphur to sulphuric acid.
If the conditions are anaerobic, thermoacidophiles may reduce to sulphur to H2S. Bicarbonates are also precipitated into the carbonate form by their activity.
Example of Thermoacidophiles: Thermoplasma and Thermococcus