[B-CG03] Earth and Planetary Science Frontiers for Life and Global Environment

[BCG03-08] The unique metabolism of hyperthermophilic archaea

★Invited Papers

*Haruyuki Atomi¹ (1.Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University)

Keywords:Archaea, Metabolism, Hyperthermophile

Archaea represent the third domain of life and are phylogenetically distinct to the Bacteria and Eucarya. Studies on their metabolism have clearly demonstrated that Archaea utilize enzymes and pathways that differ to those previously established in bacteria and eukaryotes. Thermococcus kodakarensis is a hyperthermophilic archaeon that exhibits an optimal growth temperature of 85^oC. The organism is an obligate heterotroph, and utilizes polysaccharides, peptides, amino acids, and organic acids as a carbon source and their oxidation as an energy source. The T. kodakarensis genome sequence has been determined, and gene disruption methodology has been established, enabling us to carry out both biochemical and genetic analyses on the metabolism and physiology of this organism. Here I will introduce some of the unique aspects of metabolism in T. kodakarensis and archaea in general. The majority of archaea do not utilize a pentose phosphate pathway, and the mechanisms to synthesize and degrade the ribose moieties of nucleosides and nucleotides had not been understood in these organisms. Using genome information and comparative genomics along with classical biochemistry and genetics, we have shown that the reverse flux of the ribulose monophosphate pathway and the newly identified pentose bisphosphate pathway are responsible for these conversions. I will describe pathways unique to the archaea, and by comparing the metabolism among the three domains of life, evolutionary aspects will be discussed.