Archaea

Archaea are a group of organisms, previously classified as bacteria, from which eubacte-ria and other life may have evolved. A melavonic acid (six carbon)-building block is used for synthesis instead of acetic acid. The generated phytanyl chains are attached to glycerol moieties of complex lipids by ether linkages. Thus, these lipids are unlike anything found in eubacteria or eukaryotes today. 

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One of the principal substances obtained from archaea (one of the oldest forms of life on earth) is denved from a 40 carbon diol Given the fact that this diol is optically active is it com pound A or is it compound... 

Studying evolutionary aspects, by the construction of phylogenetic trees from the pairwise differences between sequences for example, the classification with 70S, 30S RNAs established the separate kingdom of archaea... 

Ribosomes are ancient ribonucleoprotein complexes that are the sites of protein synthesis in living cells. Their core structures and fundamental functional mechanisms have been conserved throughout the three domains of life bacteria, archaea and eukaryotes. All ribosomes are organized into two subunits that are defined by their apparent sedimentation coefficient, measured in Svedberg units (S). There is a general... 

Domain Archaea Verrucomicrobia, Cytophaga-Flavobacterium, Deinococci... 

Fe Bacteria/Archaea Electron transport/ Redox sensing [Pe3S,] [Pe,S,T -140 to -460 52... 

This key enzyme of the dissimilatory sulfate reduction was isolated from all Desulfovibrio strains studied until now 135), and from some sulfur oxidizing bacteria and thermophilic Archaea 136, 137). The enzymes isolated from sulfate-reducing bacteria contain two [4Fe-4S] clusters and a flavin group (FAD) as demonstrated by visible, EPR, and Mossbauer spectroscopies. With a total molecular mass ranging from 150 to 220 kDa, APS reductases have a subunit composition of the type 012)32 or 02)3. The subunit molecular mass is approximately 70 and 20 kDa for the a and )3 subunits, respectively. Amino-acid sequence data suggest that both iron-sulfur clusters are located in the (3 subunit... 

Cell envelopes of prokaryotic organisms (archaea and bacteria) are characterized by the presence of two distinct components the cytoplasmic membrane, which constitutes the inner layer, and an outer supramolecular layered cell wall (for reviews see Ref. 4), which pre-... 

In this context it is interesting to note that archaea, which possess S-layers as exclusive cell wall components outside the cytoplasmic membrane (Fig. 14), exist under extreme environmental conditions (e.g., high temperatures, hydrostatic pressure, and salt concentrations, low pH values). Thus, it is obvious one should study the effect of proteinaceous S-layer lattices on the fluidity, integrity, structure, and stability of lipid membranes. This section focuses on the generation and characterization of composite structures that mimic the supramolecular assembly of archaeal cell envelope structures composed of a cytoplasmic membrane and a closely associated S-layer. In this biomimetic structure, either a tetraether... 

Another important area of future development concerns copying the supramolecular principle of cell envelopes of archaea, which have evolved in the most extreme and hostile ecosystems. This biomimetic approach is expected to lead to new technologies for stabilizing fnnctional lipid membranes and their nse at the mesoscopic and macroscopic scales [200]. Along the same line, liposomes coated with S-layer lattices resemble archaeal cell envelopes or virns envelopes. Since liposomes have a broad application potential, particu-... 

Archaea belonging to the kingdom Crenarchaeota deserve attention. Although it has been assumed that these are extreme thermophiles, members of this group have been identified by molecular techniques in other habitats, for example, soils (Buckley et al. 1998), boreal forest soil (Jurgens et al. 1997), and in plant extracts (Simon et al. 2005). 

Eairley DJ, DR Boyd, ND Sharma, CCR Allen, P Morgan, MJ Larkin (2002) Aerobic metabolism of 4-hydroxybenzoic acid in Archaea via an unusual pathway involving an intramolecular migration (NIH shift). Appl Environ Microbiol 68 6246-6255. 

An enzyme that catalyzes the reduction of A -piperidein-2-carboxylate to piperidine-2-car-boxylate (r-pipecolate) in the catabolism of o-lysine by Pseudomonas putida ATCC12633 is an NADPH-dependent representative of a large family of reductases that are distributed among bacteria and archaea (Muramatsu et al. 2005). It also catalyzes the reduction of A -pyrrolidine-2-carboxylate to L-proline. 

These reductases play a key role both in methanogenesis and in the degradation of phenols that carry several nitro groups, which is discussed further in Chapter 9, Part 5. Although these reductases are typically found in methanogens, they have been encountered in a number of other bacteria and archaea ... 

Methyl coenzyme M reductase plays a key role in the production of methane in archaea. It catalyzes the reduction of methyl-coenzyme M with coenzyme B to produce methane and the heterodisulfide (Figure 3.35). The enzyme is an a2P2Y2 hexamer, embedded between two molecules of the nickel-porphinoid F jg and the reaction sequence has been delineated (Ermler et al. 1997). The heterodisulfide is reduced to the sulfides HS-CoB and HS-CoM by a reductase that has been characterized in Methanosarcina thermoph-ila, and involves low-potential hemes, [Fe4S4] clusters, and a membrane-bound metha-nophenazine that contains an isoprenoid chain linked by an ether bond to phenazine (Murakami et al. 2001). 

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