Life in High-Temperature Environments

DIVERSITY OF HIGH-TEMPERATURE ENVIRONMENTS High-temperature biotopes colonized by thermophilic and hyperthermophilic microorganisms are distributed on all continents and oceans and span a huge diversity of physicochemical niches, with pH values in high-temperature spring sources spanning >7 units (1–3) and aqueous concentrations of biologically relevant elements spanning several orders of magnitude (1, 2). Studies of high-temperature environments and the thermophiles inhabiting them are motivated by a number of factors, including basic scientific foci such as the molecular bases of thermophily and thermal limits of life, biodiversity exploration, and the origin and early evolution of life. Although the setting for the origin of life is debated (4, 5), a high-temperature origin of life is strongly favored in the literature (6–9), and there is an abundance of evidence for high-temperature aquatic environments following the Late Heavy Bombardment, the time when fossil and isotopic evidence suggest that life first evolved (10–12). The study of thermophiles is also of acute interest for applied science, including microbially enhanced oil recovery and inhibition of oil souring (13), isolation of novel molecules (14), and the discovery and development of thermostable enzymes for biotechnology (15–18).