Halophiles, methanogens and thermoacidophiles belong to Archaebacteria.

Archaebacteria
Archaebacteria are a group of single-celled microorganisms that are similar to bacteria in size and simplicity of structure but differ from them in molecular organization, cell wall composition, and habitat. They are found in extreme environments such as hot springs, salt lakes, and deep-sea hydrothermal vents.

Halophiles
Halophiles are a type of Archaebacteria that live in highly saline environments such as salt lakes, salt pans, and salt mines. They are able to survive in these extreme conditions because of their unique adaptations, such as the ability to pump out excess salt and to produce pigments that protect them from UV radiation.

Methanogens
Methanogens are another type of Archaebacteria that live in anaerobic environments such as the digestive tracts of ruminants, swamps, and rice paddies. They are able to produce methane as a byproduct of their metabolism, which is important in the cycling of carbon in these environments.

Thermoacidophiles
Thermoacidophiles are a type of Archaebacteria that live in environments with high temperatures and low pH, such as hot springs and volcanic vents. They are able to survive in these extreme conditions because of their unique adaptations, such as the ability to stabilize their proteins at high temperatures and to maintain a stable internal pH.

Conclusion
In conclusion, halophiles, methanogens, and thermoacidophiles are all examples of Archaebacteria that are able to survive in extreme environments due to their unique adaptations.

Methanogens , Halophiles , Thermoacidophils , all belong to ARCHEBACTERIA they are the primitive organism means they were the first to inhabit earth , they are often called LIVING FOSSILS Methanogens are found in Rumen of cattles , Halophiles are found in salt lakes , Thermoacidophils are found in Hot sulphur springs. Archebacteria are found in some of the harsh climatic conditions where no other life form could survive