A. Gambacorta

Extremely Thermophilic Acidophilic Bacteria Convergent with Sulfolobus Acidocaldarius

A series of extremely thermophilic acidophilic bacteria has been characterized as closely resembling the species Sulfolobus acidocaldarius except for a totally different guanosine-cytosine content in the DNA; some conceptual consequences of this situation are discussed. Both organisms also share special features, including a very characteristic type of ether lipid, with other extreme acidophilic thermophiles.

Archaeal lipids and their biotechnological applications

The lipids of Archaea, based on glycerol isopranoid ethers, can be used taxonomically to distinguish between phenotypic subgroups of the domain to delineate them clearly from all other organisms. This review is a general survey of the structural features of archaeal lipids and how they relate to survival in the harsh environments in which the Archaea live. The molecular organization of archaeal lipids in monolayers, artificial black membranes and vesicles and the unique properties and possible biotechnological applications of liposomes of the lipids are presented. The results with these liposomes are compared with similar data obtained with synthetic compounds which mimic the structure of archaeal lipids. Studies on computer simulation are also reported.

An Asymmetric Archaebacterial Diether Lipid from Alkaliphilic Halop hile s

SUMMARY: Archaebacterial halophiles from alkaline soda lakes were shown to possess substantial amounts of a core diether lipid differing from the C20,C20 diether lipid characteristic of Halococcus and Halobacterium spp. This novel diether lipid was shown to be an asymmetric C20,C25 diether (2-O-sesterterpanyl-3-0-phytanyl-sn-glycerol). The implications of this unusual lipid for membrane structure are discussed.

S‐Adenosylmethionine synthetase in the thermophilic archaebacterium Sulfolobus solfataricus.

Two isoforms of methionine adenosyltransferase (S-adenosylmethionine synthetase), A and B, have been partially purified from Sulfolobus solfataricus, a thermophilic archaebacterium optimally growing at 87 degrees C. The chromatographic procedure, involving hydrophobic chromatography on a phenyl-Sepharose column as a major step, results in 330-fold and 150-fold purification of adenosylmethionine synthetase A and B respectively. The apparent molecular masses, estimated by gel filtration, are 180 kDa for A and 75 kDa for B. The A and B isoforms follow Michaelis-Menten kinetics with apparent Km values of 10 microM and 20 microM for L-methionine and of 50 microM and 150 microM for ATP respectively. Adenosylmethionine, a product of the reaction, acts as a powerful non-competitive inhibitor (Ki = 50 microM) of the A isoform while it inhibits only slightly the B isoform. Both isozymes exhibit tripolyphosphatase activity but only that associated with the form A is stimulated by 5 microM adenosylmethionine concentration. The two enzymes absolutely require a divalent cation for the activity, but are not affected by monovalent ions and reducing agents. The optimum temperature is 90 degrees C and no significant loss of activity is observable after incubation of the two isoforms at 100 degrees C in the presence of ATP. The Arrhenius plots observed for both isozymes are biphasic, indicating different activation energies below and above 75 degrees C. The cytoplasmic levels of ATP, methionine and adenosylmethionine are evaluated.

A C25,C25 Diether Core Lipid from Archaebacterial Haloalkaliphiles

SUMMARY: The membrane lipids from an archaebacterial haloalkaliphile were shown to be based almost entirely on diethers containing C25 isopranyl chains. The ‘universal’ C20,C20 archaebacterial diether core lipid (2,3-di-O-phytanyl-sn-glycerol) made up only 9% (w/w) of the total isopranoid diether fraction. The rest of the isopranoid diether fraction comprised 85% (w/w) C20,C25 diether (2-O-sesterterpanyl-3-O-phytanyl-sn-glycerol) and 6% (w/w) of a novel C25,C25 diether (2,3-di-O-sesterterpanyl-sn-glycerol).

Cyclohexane fatty acids from a thermophilic bacterium

In the saponifiable lipids of Bacillus acidocaldarius the principal components are 11-cyclohexylundecanoic and 13-cyclohexyltridecanoic acids.

Polar lipids in methanogen taxonomy

Summary: Polar lipid patterns of representative methanogens were recorded by two-dimensional thin-layer chromatography. Phenotypically similar Methanobacterium spp., Methanobrevibacter spp. and Methanomicrobium spp. could readily be distinguished from each other. Similarly, Methanogenium spp. and phenotypically similar Methanococcus spp. had different polar lipid patterns. Single examples from the monospecific genera Methanospirillum, Methanoplanus and Methanothermus had distinctive polar lipid patterns, but Methanolobus tindarius had a similar pattern to Methanosarcina spp. The isopranoid ether lipid cores from the polar lipids were identical for those species within any one genus. Novel core lipids were identified in examples from the genera Methanomicrobium, Methanosarcina and Methanolobus.

Artificial black membranes from bipolar lipids of thermophilic Archaebacteria.

The membrane of thermophilic archaebacteria is characterized by the presence of unusual isoprenoid bipolar lipids. The molecular organization of these lipids is still a matter of study. Important information could come from forming artificial black membranes. Black films can be formed from n-alkane or squalene dispersions of bipolar lipids extracted from the membrane of Caldariella acidophila. Membrane formation occurred only above a critical temperature (approximately 70 degrees C) corresponding to the physiological one. At lower temperatures, special solvent systems (n-alkanes or squalene, butanol and n-alkanes or squalene, butanol chloroform) were required. To characterize the physical parameters of these membranes, conductance and capacitance measurements were performed. Conductance was in the range of 10(-8) - 10(-7) omega -1 cm -2 , where specific capacitance at T = 72 degrees C was Cs = 0.685 +/- 0.004 microF/cm2 and Cs = 0.658 +/- 0.08 microF/cm2, corresponding to a dielectric thickness of 27 and 29 A for squalene and dodecane dispersions, respectively. Capacitance was shown to vary as the square of membrane potential, as usual in lipid bilayers. Values of the proportionality constant alpha have been compared to those of solvent-containing and solvent-free bilayers. The behavior of capacitance as a function of temperature is also shown by lowering temperature; the occurrence of complex structural changes was indicated. All the experimental data suggest that the presence of solvent is very low. Two possible molecular configurations of the films are discussed.

Structure and properties of a thermophilic and thermostable DNA polymerase isolated from Sulfolobus solfataricus

Summary A DNA-dependent DNA polymerase activity was purified to homogeneity from the archaebacterium Sulfolobus solfataricus , grown at 87°C and pH 3.5. This activity was the most abundant (80–85%) of two chromatographically distinguishable DNA polymerases. The enzyme purified about 1000-fold had a Mr of 210,000 ± 10,000 as determined by gel filtration. SDS gel electrophoresis revealed the presence of three peptides with a Mr of 116,000, 53,000 and 37,000, respectively, of which only the 116,000 subunit showed activity after elution from the gel and renaturation. However, by glycerol gradient centrifugation a Mr of 115,000 ± 5,000 was obtained. The DNA polymerase, assayed at 75°C and pH 6.8, required activated DNA and Mg ++ or Mn ++ for its activity and was thermophilic and thermostable. The temperature at which the activity was optimal depended on the type of DNA used as template-primer. It was concluded that the activity decreased at high temperature because of the melting of the template-primer, not as a result of enzyme inactivation. The DNA polymerase was also characterized with respect to its behaviour with inhibitors used to discriminate between enzymes isolated from prokaryotes or eukaryotes.

Comparative Lipid Composition of Aerobically and Anaerobically Grown Desulfurolobus ambivalens, an Autotrophic Thermophilic Archaeobacterium

Summary: Lipids from the autotrophic thermophilic archaeobacterium Desulfwolobus ambivalens grown under aerobic and anaerobic conditions were analysed and compared with those of Sulfolobus solfataricus, a related micro-organism. The ether lipids of aerobically and anaerobically grown D. ambivalens, as well as those of S. solfataricus, had the same general features except for the degree of cyclization of the C40 isopranic chains. The quinone content of D. ambivalens was strongly affected by growth conditions. Aerobically grown cells contained caldariellaquinone, 6-(3,7,11,15,19,23-hexamethyltetracosyl)-5-methylthiobenzo[b]thiophen-4,7-quinone (83% of the quinone pool), sulfolobusquinone, 6-(3,7,11,15,19,23-hexamethyltetracosyl)-5-methyl-benzo[b]thiophen-4,7-quinone (16%) and the tricyclic quinone benzo[1,2-b; 4,5-b]dithiophen-4,8-quinone (trace amounts). In anaerobically grown D. ambivalens sulfolobusquinone was the only quinone present.