from Kazem Kashefi writing in Extremophiles: Microbiology and Biotechnology:
The isolation and characterization of novel hyperthermophilic, microorganisms from modern hot environments have greatly increased our understanding of how microbes can live and thrive in such inhospitable environments. The finding that microorganisms have the ability to grow at these high temperature has implications for delimiting when and where life might have evolved on a hot, early Earth; the depth to which life exists in the Earth's subsurface; and the potential for life in hot, extraterrestrial environments. The study of hyperthermophilic microorganisms provides valuable insights into microbial respiration in a diversity of modern and ancient hydrothermal systems. In addition, it provides information about the fate of metals such as iron, uranium, technetium, and even gold. Reduction of these metals by hyperthermophiles provides, for example, a likely explanation for a number of geologically, environmentally and economically important ore deposits. This allows us to identify geological signatures for biological processes, something that may prove instrumental in our search for life on other planets. Finally, enzymes capable of functioning at high temperatures have a number of important applications in biomass conversion, in biotechnology, and in the pharmaceutical, food and cosmetic industries.
Further reading: Extremophiles: Microbiology and Biotechnology