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Carbonic anhydrases catalyze the reversible hydration of [CO.sub.2] and are ubiquitous in highly evolved eukaryotes. The recent identification of a third class of carbonic anhydrase ([Gamma] class) in a methanoarchaeon and our present finding that the [Beta] class also extends into thermophilic species from the Archaea domain led us to initiate a systematic search for these enzymes in metabolically and phylogenetically diverse prokaryotes. Here we show that carbonic anhydrase is widespread in the Archaea and Bacteria domains, and is an ancient enzyme. The occurrence in chemolithoautotrophic species occupying deep branches of the universal phylogenetic tree suggests a role for this enzyme in the proposed autotrophic origin of life. The presence of the [Beta] and [Gamma] classes in metabolically diverse species spanning the Archaea and Bacteria domains demonstrates that carbonic anhydrases have a far more extensive and fundamental role in prokaryotic biology than previously recognized.

Organisms that survive in what humans would consider harsh environments are of interest because they are unusual and because their biochemistry and molecular biology function under regimes of high temperature [...]

Research is presented concerning the use of archaebacterial lipids for the formation of defect-free self-assembled monolayers. The synthesis of an archae lipid mimic phytanylthiol is discussed.

Proteolysis, the last step in the life of a protein, is essential for the maintenance of cellular homeostasis (1). Proteases remove damaged or denatured proteins, recycle their amino acids, and [...]

Halobacterium halobium, a one billion-year-old archaebacterium, grows a purple membrane containing bacteriorhodopsin which, in addition to inducing proton-pumping with the resultant ATP synthesis, exhibits oscillations. These oscillations may be due to simultaneous positive feedback from proton pumping and may be a biological equivalent of the principle that frequency control is superior to amplitude control. Alternatively, the oscillation phenomenon may lead to thermodynamic equilibrium.

Prokaryotes Archaea, which were considered unimportant for global ecology due to their extreme habitats, occupy wide areas of ocean floors. Archaea, which are more akin to humans than bacteria, fall into two subgroups, methanogenic and halophilic types on the one hand and the more advanced ocean-living thermophilic Crenarchaeota on the other. The Archaea also show group-specific RNAs.

Isolation of Extremely Thermophilic Sulfate Reducers: Evidence for a Novel Branch of Archaebacteria TWO MAIN SUBDIVISION OF ARCHAEBACTERIAare distinguished: one comprising the methanogenic bacteria and the extreme halophiles, and a [...]

The Archaea are valuable for studying basic biological questions and have novel biotechnology applications Microbial life has inhabited this planet for approximately 3.7 billion years - 3 billion years longer [...]

Archaea employ the same general approaches in adapting to increased osmotic stress as eubacterial and eukaryotic organisms, but they are remarkable for the unusual organic osmolytes accumulated. Among these unique osmolytes are inorganic ions, salt-tolerant enzymes as well as organic solutes such as sugars and polyhydric alcohols, alpha-amino acids and derivatives, beta-amino acids and derivatives, and miscellaneous osmolytes such as cyclic-2,3-diphosphoglycerate and 1,3,4,6-tetracarboxyhexane. Some of the biosynthetic pathways or uptake systems for osmolytes are discussed.

Novel symmetrical and unsymmetrical archaeal glycolipid analogues have been synthesized based on the elaboration of lipid cores from versatile chiral starting materials and simultaneous or sequential introduction of polar headgroups. These glycolipid analogues include, presumably for the first time, galactose units in a furanose cyclic form and lactose or phosphate moieties. An interesting method for the construction of the lipidic backbone that permitted the efficient access of chiral diols on a large scale was developed, whose flexibility was confirmed by the preparation of a new hemimacrocyclic diol bearing a cyclopentane unit.

Patrick Forterre, a molecular biologist at the University of Paris's campus in Orsay, cannot believe his good luck. For much of his career, Forterre has been studying a strange group [...]

A study was conducted to examine the effects of fluctuations in environmental salinity on the primary sequence and tertiary structure of halophilic archaea. Results indicate that fluctuating environmental salinity drives halophilic genes to produce higher proportions of nonsynomymous nucleotide substitutions that, in effect, inhibits the fitness optimization of these organisms. It was also noted that the drop on environmental salinity explains the unusual evolutionary divergence of the archaea's encoding genes.