High impact information on Crenarchaeota

• Three endonuclease structures are known in the Archaea: a homotetramer in some Euryarchaea, a homodimer in other Euryarchaea, and a heterotetramer in the Crenarchaeota [1].
• We also find that a combined data set of EF-Tu and EF-G sequences favors placement of the eukaryotes within the Archaea, as the sister group to the Crenarchaeota [2].
• Although many species of Crenarchaeota (one of the two recognized archaeal kingdoms sensu Woese [Woese, C. R., Kandler, O. & Wheelis, M. L. (1990) Proc. Natl. Acad. Sci. USA 87, 4576-4579]) have been isolated, they constitute a relatively tight-knit cluster of lineages in phylogenetic analyses of rRNA sequences [3].
• H. volcanii small subunit rRNA appears to reflect the phenotypically low modification level in the Crenarchaeota kingdom and is the only cytoplasmic small subunit rRNA shown to lack pseudouridine [4].
• The extremely thermostable NAD-dependent glutamate dehydrogenase (NAD-GluDH) from Pyrobaculum islandicum, a member of the Crenarchaeota, was crystallized, and its 3D structure has been determined by X-ray diffraction methods [5].

Biological context of Crenarchaeota

• This prevents the dense packing characteristic for the cyclopentane ring-containing GDGTs membrane lipids used by hyperthermophilic crenarchaeota to adjust their membrane fluidity to high temperatures [6].
• In the 23S rRNA gene, we detected a homing-endonuclease encoding a group I intron similar to those detected in hyperthermophilic Crenarchaeota and Bacteria, as well as eukaryotic organelles [7].

Associations of Crenarchaeota with chemical compounds

• The latter group inherited the biosynthetic capabilities for a membrane composed of cyclopentane ring-containing GDGTs from the (hyper)thermophilic crenarchaeota [6].
• Its structure is similar to that of GDGTs biosynthesized by (hyper)thermophilic crenarchaeota apart from the cyclohexane ring [6].
• Crenarchaeol: the characteristic core glycerol dibiphytanyl glycerol tetraether membrane lipid of cosmopolitan pelagic crenarchaeota [6].
• Novel genes for nitrite reductase and Amo-related proteins indicate a role of uncultivated mesophilic crenarchaeota in nitrogen cycling [8].
• Presence of acetyl coenzyme A (CoA) carboxylase and propionyl-CoA carboxylase in autotrophic Crenarchaeota and indication for operation of a 3-hydroxypropionate cycle in autotrophic carbon fixation [9].

Gene context of Crenarchaeota

• Other clones exhibited intermediate phylogenetic affiliation between soil clones and MGI in the Crenarchaeota [10].
• Phylogenetic analyses of the rRNA genes and of several protein encoding genes (e.g. DNA polymerase, FixAB, glycosyl transferase) confirmed the specific affiliation of the genomic fragment with the non-thermophilic clade of the crenarchaeota [11].

References