Anion inhibition studies of an α-carbonic anhydrase from the thermophilic bacterium Sulfurihydrogenibium yellowstonense YO3AOP1.

The newly discovered thermophilic bacterium Sulfurihydrogenibium yellowstonense YO3AOP1 encodes an α-carbonic anhydrases (CAs, EC 4.2.1.1) which is highly catalytically active and thermostable. Here we report the inhibition of this enzyme, denominated SspCA, with inorganic and complex anions and other molecules interacting with zinc proteins. SspCA was inhibited in the micromolar range by diethyldithiocarbamate, sulfamide, sulfamic acid, phenylboronic and phenylarsonic acid, trithiocarbonate and selenocyanide (K(I)s of 4-70 µM) and in the submillimolar one by iodide, cyanide, (thio)cyanate, hydrogen sulfide, azide, nitrate, nitrite, many complex anions incorporating heavy metal ions and iminodisulfonate (K(I)s of 0.48-0.86 mM). SspCA was not substantially inhibited by bicarbonate and carbonate, hydrogensulfite and peroxidisulfate (K(I)s in the range of 21.1-84.6mM). The exceptional thermostability and lack of strong affinity for hydrogensulfide, bicarbonate, and carbonate make this enzyme an interesting candidate for biotechnological applications of enzymatic CO(2) fixation.

[Strain polymorphism of the plasmid profiles in Acidithiobacillus ferrooxidans]. / Shtammovyi polimorfizm plazmidnykh profilei u Acidithiobacillus ferrooxidans.

Plasmid profiles were studied in 27 Acidithiobacillus ferrooxidans strains isolated from different geographic zones and substrates differing in the composition of the main sulfide minerals, and also in experimentally obtained strains with acquired enhanced resistance to the ions of heavy metals (Fe, Ni, Cu, Zn, As). In 16 out of 20 strains isolated from different substrates, one to four 2- to 20-kb and larger plasmids were revealed. Plasmids were found in all five strains isolated from gold-containing pyrite-arsenopyrite ores and concentrates, in nine of 11 strains isolated from the ores and concentrates containing nonferrous metals, and in two of four strains isolated from the oxidation substrates of simple composition (mine waters, pyritized coals, active sludge). Changes in the plasmid profiles in some A. ferrooxidans strains (TFZ, TFI-Fe, TFV-1-Cu) with experimentally enhanced resistance to Zn2+, Fe3+, and Cu2+, respectively, were noted as compared with the initial strains. After 30 passages on S0-containing medium, strain TFBk showed changes in the copy number of plasmids. The role of plasmids in the processes of oxidation of energy substrates and in the acquired enhanced resistance to the heavy metal ions is discussed.

Purification and properties of a thermostable fumarate hydratase from the archaeobacterium Sulfolobus solfataricus.

Fumarate hydratase (EC 4.2.1.2) from the extremely thermophilic archaeobacterium Solfolobus solfataricus has been purified to homogeneity by a rapid purification procedure using affinity chromatography and high-performance size-exclusion chromatography, and the enzyme's physical and biochemical properties have been determined. The native enzyme has a molecular mass of 170 kDa and is composed of identical subunits with a molecular mass of 45 kDa, thus indicating a tetrameric structure similar to fumarases isolated from other organisms. The enzyme was active at temperatures ranging from 40 degrees C to 90 degrees C, with a maximum activity at 85 degrees C. The pH optimum for generation of fumarate was found to be pH 8.0. The enzyme showed high stability to denaturation by heat and organic solvents.

Effect of organic substrates on biological sulphide oxidation.

Neither acetate nor higher fatty acids and glucose have a significant effect on the biotechnological process for sulphide removal at 20 degrees C, in which sulphide is oxidized to sulphur using oxygen. The oxidation of acetate and propionate with oxygen is mainly dependent on the sulphide and oxygen concentrations in the reactor. The occurrence of Thiothrix filaments in sulphide-removing waste-water treatment systems has been investigated using a fixer-film upflow reactor. The influent of this reactor consisted of anaerobically treated paper-mill waste-water, with a sulphide concentration of 140 mg/l. It was found that sulphide loading rate is the decisive parameter as to whether or not Thiothrix will develop in a sulphide-removing reactor.