Central metabolism of Archaea

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The Archaea form the third domain of life and possess many genetical, structural and biochemical features which are considered to be ancestral. An interesting feature of Archaea is a great diversity of their central metabolic pathways, many of which have never been identified in either Bacteria or Eukarya. In the last years, we have identified two novel autotrophic CO2 assimilation pathways in Crenarchaeota and an unusual acetate assimilation pathway in haloarchaea. Although these and other studies substantially increased our understanding of the archaeal physiology and biochemistry, they also identified several gaps in our knowledge of archaeal central metabolic pathways. Such gaps are: (i) the gene encoding 4-hydroxybutyrate-CoA ligase in Metallosphaera sedula is not known and should be identified and characterized; (ii) the pathway of autotrophic CO2 fixation in mesophilic marine group I Archaea (‘Thaumarchaeota’) remains to be proven biochemically; (iii) the pathway of autotrophic CO2 fixation in some Pyrobaculum species is unknown; (iv) the methylaspartate cycle of acetyl-CoA assimilation in Haloarcula marismortui requires further experimental support as well as identification and characterization of its key enzymes. These questions will be addressed experimentally using different microbiological, biochemical and genetical approaches.