Hyperthermophile

About: Hyperthermophile is a research topic. Over the lifetime, 648 publications have been published within this topic receiving 30308 citations.

Hyperthermophilic Enzymes: Sources, Uses, and Molecular Mechanisms for Thermostability

Abstract: Enzymes synthesized by hyperthermophiles (bacteria and archaea with optimal growth temperatures of >80°C), also called hyperthermophilic enzymes, are typically thermostable (i.e., resistant to irreversible inactivation at high temperatures) and are optimally active at high temperatures. These enzymes share the same catalytic mechanisms with their mesophilic counterparts. When cloned and expressed in mesophilic hosts, hyperthermophilic enzymes usually retain their thermal properties, indicating that these properties are genetically encoded. Sequence alignments, amino acid content comparisons, crystal structure comparisons, and mutagenesis experiments indicate that hyperthermophilic enzymes are, indeed, very similar to their mesophilic homologues. No single mechanism is responsible for the remarkable stability of hyperthermophilic enzymes. Increased thermostability must be found, instead, in a small number of highly specific alterations that often do not obey any obvious traffic rules. After briefly discussing the diversity of hyperthermophilic organisms, this review concentrates on the remarkable thermostability of their enzymes. The biochemical and molecular properties of hyperthermophilic enzymes are described. Mechanisms responsible for protein inactivation are reviewed. The molecular mechanisms involved in protein thermostabilization are discussed, including ion pairs, hydrogen bonds, hydrophobic interactions, disulfide bridges, packing, decrease of the entropy of unfolding, and intersubunit interactions. Finally, current uses and potential applications of thermophilic and hyperthermophilic enzymes as research reagents and as catalysts for industrial processes are described.

Hyperthermophilic archaea are thriving in deep North Sea and Alaskan oil reservoirs

Abstract: HOT springs and hydrothermal vents harbour hyperthermophilic archaea and bacteria with the highest growth temperatures known1–6. Here we report the discovery of high concentrations of hyperthermophiles in the production fluids from four oil reservoirs about 3,000 metres below the bed of the North Sea and below the permafrost surface of the North Slope of Alaska. Enrichment cultures of sulphidogens grew at 85 °C and 102 °C, which are similar to in situ reservoir temperatures7,8. Some species were identical to those from submarine hot vents and may have entered the reservoirs in injected sea water. Several enrichments grew anaerobically in sterilized artificial sea water with crude oil as the single carbon and energy source. These hyperthermophiles may be part of novel high-temperature communities and could be responsible for in situ bioconversions of crude oil fractions at temperatures previously considered too extreme for biochemical reactions4,7,9,10.

Complete genome sequence of the hyperthermophilic archaeon Thermococcus kodakaraensis KOD1 and comparison with Pyrococcus genomes

Abstract: The euryarchaeal order Thermococcales, composed of two major genera Thermococcus and Pyrococcus (Huber and Stetter 2001; Itoh 2003), may be the best-studied hyperthermophiles. They are strictly anaerobic obligate heterotrophs growing on complex proteinaceous substrates, and their growth is strongly associated with the reduction of elemental sulfur. Alternatively, with a few exceptions, they are capable of gaining energy by fermentation of peptides, amino acids, and sugars, forming acids, CO2, and H2 in the absence of elemental sulfur (Amend and Shock 2001; Huber and Stetter 2001). The genus Pyrococcus, with a higher optimum growth temperature (95°C-103°C) than Thermococcus (75°C-93°C), has fascinated many microbiological researchers and has often been used as the source organism for both fundamental and application-based aspects of research. Therefore, although within the same genus, the complete genome analyses of three species—Pyrococcus horikoshii (Kawarabayasi et al. 1998), Pyrococcus furiosus (Robb et al. 2001), and Pyrococcus abyssi (Cohen et al. 2003)—have been performed. In contrast to Pyrococcus, the genus Thermococcus contains the highest number of characterized isolates (Itoh 2003). Recent culture-dependent and culture-independent studies have indicated that the members of Thermococcus are more ubiquitously present in various deep-sea hydrothermal vent systems than those of Pyrococcus (Orphan et al. 2000; Holden et al. 2001). Consequently, Thermococcus strains, with their larger population, are considered to play a major role in the ecology and metabolic activity of microbial consortia within marine hot-water ecosystems. However, despite the importance of this genus, no complete genome sequence has been determined for Thermococcus. The Thermococcus genome can be expected to encode genes responsible for various cellular functions that provide an advantage for these strains in natural high-temperature habitats. Thermococcus kodakaraensis KOD1 was isolated from a solfatara on the shore of Kodakara Island, Kagoshima, Japan (Morikawa et al. 1994; Atomi et al. 2004). Since the isolation, an abundant number of genes and their protein products from this archaeon have been examined (Imanaka and Atomi 2002), such as DNA polymerase, commercially available as an excellent enzyme for PCR amplification (Nishioka et al. 2001). Moreover, as we recently developed the first gene disruption system for a hyperthermophile with this archaeon (Sato et al. 2003), T. kodakaraensis can be regarded as one of the most useful model organisms in the research on hyperthermophiles. Here we describe the complete genome analysis of T. kodakaraensis KOD1 as well as a comparison with Pyrococcus genomes, to gain further insight into the intriguing order Thermococcales.