title: Hyperthermophily and the origin and earliest evolution of life.
abstract: The possibility of a high-temperature origin of life has gained support based on indirect evidence of a hot, early Earth and on the basal position of hyperthermophilic organisms in rRNA-based phylogenies. However, although the availability of more than 80 completely sequenced cellular genomes has led to the identification of hyperthermophilic-specific traits, such as a trend towards smaller genomes, reduced protein-encoding gene sizes, and glutamic-acid-rich simple sequences, none of these characteristics are in themselves an indication of primitiveness. There is no geological evidence for the physical setting in which life arose, but current models suggest that the Earth's surface cooled down rapidly. Moreover, at 100 degrees C the half-lives of several organic compounds, including ribose, nucleobases, and amino acids, which are generally thought to have been essential for the emergence of the first living systems, are too short to allow for their accumulation in the prebiotic environment. Accordingly, if hyperthermophily is not truly primordial, then heat-loving lifestyles may be relics of a secondary adaptation that evolved after the origin of life, and before or soon after separation of the major lineages.
authors.affiliation: Facultad de Ciencias, UNAM, Ciudad Universitaria, 04510 México D.F., México.
authors.forename: Sara
authors.initials: S
authors.lastname: Islas
authors.forename: Ana M
authors.initials: AM
authors.lastname: Velasco
authors.forename: Arturo
authors.initials: A
authors.lastname: Becerra
authors.forename: Luis
authors.initials: L
authors.lastname: Delaye
authors.forename: Antonio
authors.initials: A
authors.lastname: Lazcano
mesh_terms: D000222:Adaptation, Physiological; D001105:Archaea / Q000235:genetics / Q000502:physiology; D005075:Biological Evolution; D004247:DNA / Q000235:genetics; D016678:Genome; D006358:Hot Temperature; D008954:Models, Biological; D000069497:Origin of Life; D011387:Prokaryotic Cells; D012335:RNA, Ribosomal / Q000235:genetics
chemical_list: D012335:RNA, Ribosomal; D004247:DNA