Extremophiles Extremophiles are a collection of microorganisms classified according to the following four parameters: High and low temperature:thermophiles and psychrophiles High and low pH:alkaliphiles and acidophiles High salt concentration:halophiles High pressure:barophilesExtremophiles Extremophiles are a collection of microorganisms classified according to the following four parameters: • High and low temperature: thermophiles and psychrophiles • High and low pH: alkaliphiles and acidophiles • High salt concentration: halophiles • High pressure: barophiles