ABSTRACT
Thermophilic microorganisms have been known for a long time but usually considered as some sort of biological eccentrics. The discovery of several new extremely thermophilic and hyperthermophilic bacteria during the last few years, and the fact that almost all of them belonged to the archaea made the area even more exciting. In view of this, it is not surprising that thermophilic archaea have received much attention in the last few years and that thermophilic bacteria have been overshadowed. This chapter discusses the main properties and differences of bacteria and archaea. The diversity, ecology, and evolution of thermophiles are also briefly reviewed. All members of the sulfur-utilizing archaea, with the exception of the moderate thermophile Thermoplasma acidophilum, have been isolated only from geothermal areas. The biotechnological interest will further stimulate the basic research on thermophiles and lead to much new knowledge in this field in the future.
