The concurrence of microorganisms in niches that are hostile like extremes of temperature,
pH, salt concentration and high pressure depends upon novel molecular mechanisms to enhance the
stability of their proteins, nucleic acids, lipids and cell membranes. The structural, physiological and
genomic features of extremophiles that make them capable of withstanding extremely selective environmental
conditions are particularly fascinating. Highly stable enzymes exhibiting several industrial
and biotechnological properties are being isolated and purified from these extremophiles. Successful
gene cloning of the purified extremozymes in the mesophilic hosts has already been done. Various extremozymes
such as amylase, lipase, xylanase, cellulase and protease from thermophiles, halothermophiles
and psychrophiles are of industrial interests due to their enhanced stability at forbidding conditions.
In this review, we made an attempt to point out the unique features of extremophiles, particularly
thermophiles and psychrophiles, at the structural, genomic and proteomic levels, which allow for
functionality at harsh conditions focusing on the temperature tolerance by them.