(1/36) Interaction-induced redox switch in the electron transfer complex rusticyanin-cytochrome c(4).

The blue copper protein rusticyanin isolated from the acidophilic proteobacterium Thiobacillus ferrooxidans displays a pH-dependent redox midpoint potential with a pK value of 7 on the oxidized form of the protein. The nature of the alterations of optical and EPR spectra observed above the pK value indicated that the redox-linked deprotonation occurs on the epsilon-nitrogen of the histidine ligands to the copper ion. Complex formation between rusticyanin and its probable electron transfer partner, cytochrome c(4), induced a decrease of rusticyanin's redox midpoint potential by more than 100 mV together with spectral changes similar to those observed above the pK value of the free form. Complex formation thus substantially modifies the pK value of the surface-exposed histidine ligand to the copper ion and thereby tunes the redox midpoint potential of the copper site. Comparisons with reports on other blue copper proteins suggest that the surface-exposed histidine ligand is employed as a redox tuning device by many members of this group of soluble electron carriers.  (+info)

(2/36) Effect of various ions, pH, and osmotic pressure on oxidation of elemental sulfur by Thiobacillus thiooxidans.

The oxidation of elemental sulfur by Thiobacillus thiooxidans was studied at pH 2.3, 4.5, and 7.0 in the presence of different concentrations of various anions (sulfate, phosphate, chloride, nitrate, and fluoride) and cations (potassium, sodium, lithium, rubidium, and cesium). The results agree with the expected response of this acidophilic bacterium to charge neutralization of colloids by ions, pH-dependent membrane permeability of ions, and osmotic pressure.  (+info)

(3/36) The chromosomal arsenic resistance genes of Thiobacillus ferrooxidans have an unusual arrangement and confer increased arsenic and antimony resistance to Escherichia coli.

The chromosomal arsenic resistance genes of the acidophilic, chemolithoautotrophic, biomining bacterium Thiobacillus ferrooxidans were cloned and sequenced. Homologues of four arsenic resistance genes, arsB, arsC, arsH, and a putative arsR gene, were identified. The T. ferrooxidans arsB (arsenite export) and arsC (arsenate reductase) gene products were functional when they were cloned in an Escherichia coli ars deletion mutant and conferred increased resistance to arsenite, arsenate, and antimony. Therefore, despite the fact that the ars genes originated from an obligately acidophilic bacterium, they were functional in E. coli. Although T. ferrooxidans is gram negative, its ArsC was more closely related to the ArsC molecules of gram-positive bacteria. Furthermore, a functional trxA (thioredoxin) gene was required for ArsC-mediated arsenate resistance in E. coli; this finding confirmed the gram-positive ArsC-like status of this resistance and indicated that the division of ArsC molecules based on Gram staining results is artificial. Although arsH was expressed in an E. coli-derived in vitro transcription-translation system, ArsH was not required for and did not enhance arsenic resistance in E. coli. The T. ferrooxidans ars genes were arranged in an unusual manner, and the putative arsR and arsC genes and the arsBH genes were translated in opposite directions. This divergent orientation was conserved in the four T. ferrooxidans strains investigated.  (+info)

(4/36) Development and application of small-subunit rRNA probes for assessment of selected Thiobacillus species and members of the genus Acidiphilium.

Culture-dependent studies have implicated sulfur-oxidizing bacteria as the causative agents of acid mine drainage and concrete corrosion in sewers. Thiobacillus species are considered the major representatives of the acid-producing bacteria in these environments. Small-subunit rRNA genes from all of the Thiobacillus and Acidiphilium species catalogued by the Ribosomal Database Project were identified and used to design oligonucleotide DNA probes. Two oligonucleotide probes were synthesized to complement variable regions of 16S rRNA in the following acidophilic bacteria: Thiobacillus ferrooxidans and T. thiooxidans (probe Thio820) and members of the genus Acidiphilium (probe Acdp821). Using (32)P radiolabels, probe specificity was characterized by hybridization dissociation temperature (T(d)) with membrane-immobilized RNA extracted from a suite of 21 strains representing three groups of bacteria. Fluorochrome-conjugated probes were evaluated for use with fluorescent in situ hybridization (FISH) at the experimentally determined T(d)s. FISH was used to identify and enumerate bacteria in laboratory reactors and environmental samples. Probing of laboratory reactors inoculated with a mixed culture of acidophilic bacteria validated the ability of the oligonucleotide probes to track specific cell numbers with time. Additionally, probing of sediments from an active acid mine drainage site in Colorado demonstrated the ability to identify numbers of active bacteria in natural environments that contain high concentrations of metals, associated precipitates, and other mineral debris.  (+info)

(5/36) Purification and properties of thiosulfate dehydrogenase from Acidithiobacillus thiooxidans JCM7814.

A key enzyme of the thiosulfate oxidation pathway in Acidithiobacillus thiooxidans JCM7814 was investigated. As a result of assaying the enzymatic activities of thiosulfate dehydrogenase, rhodanese, and thiosulfate reductase at 5.5 of intracellular pH, the activity of thiosulfate dehydrogenase was measured as the key enzyme. The thiosulfate dehydrogenase of A. thiooxidans JCM7814 was purified using three chromatographies. The purified sample was electrophoretically homogeneous. The molecular mass of the enzyme was 27.9 kDa and it was a monomer. This enzyme had cytochrome c. The optimum pH and temperature of this enzyme were 3.5 and 35 degrees C. The enzyme was stable in the pH range from 5 to 7, and it was stable up to 45 degrees C. The isoelectric point of the enzyme was 8.9. This enzyme reacted with thiosulfate as a substrate. The Km was 0.81 mM.  (+info)

(6/36) Purificantion and characterization of inorganic pyrophosphatase from Thiobacillus thiooxidans.

An inorganic pyrophosphatase [EC] was isolated from Thiobacillus thiooxidans and purified 975-fold to a state of apparent homogeneity. The enzyme catalyzed the hydrolysis of inorganic pyrophosphate and no activity was found with a variety of other phosphate esters. The cation Mg2+ was required for maximum activity; Co2+ and Mn2+ supported 25 per cent and 10.6 per cent of the activity with Mg2+, respectively. The pH optimum was 8.8. The molecular weight was estimated to be 88,000 by gel filtration and SDS gel electrophoresis, and the enzyme consisted of four identical subunits. The isoelectric point was found to be 5.05. The enzyme was exceptionally heat-stable in the presence of 0.01 M Mg2+.  (+info)

(7/36) Analysis of differential-expressed proteins of Acidithiobacillus ferrooxidans grown under phosphate starvation.

Acidithiobacillus ferrooxidans is one of the most important bacterium used in bioleaching, and can utilize Fe(2+) or sulphide as energy source. Growth curves for Acidithiobacillus ferrooxidans under phosphate starvation and normal condition have been tested, showing lag, logarithmic, stationary and aging phases as seen in other bacteria. The logarithmic phases were from 10 to 32 hours for Acidithiobacillus ferrooxidans cultivated with normal cultivating condition and from 20 to 60 hrs for Acidithiobacillus ferrooxidans cultivated phosphate starvation. Differences of protein patterns of Acidithiobacillus ferrooxidans growing in case of normal or phosphate starvation were separately investigated after cultivation at 30(o)C by the analysis of two-dimensional gel electrophoresis (2-DE), matrix-assisted laser desorption/ionization (MALDI)-Mass spectrometry. There were total 6 protein spots identified, which were Recombination protein recA, RNA helicase, AP2 domain-containing transcription factor, NADH dehydrogenase I chain D, Hyothetical protein PF1669, and Transaldolase STY3758. From the 6 identified protein spots, 3 proteins were found to be decreased in expression at the cultivating condition of phosphate starvation, while another three upregulated.  (+info)

(8/36) Simultaneous removal of H2S and NH3 in biofilter inoculated with Acidithiobacillus thiooxidans TAS.

H2S and NH3 gases are toxic, corrosive and malodorous air pollutants. Although there are numerous well-established physicochemical techniques presently available for the treatment of these gases, the growing demand for a more economical and improved process has prompted investigations into biological alternatives. In biological treatment methods, H2S is oxidized to SO4(2-) by sulfur-oxidizing bacteria, and then NH3 is removed by chemical neutralization with SO4(2-) to (NH4)2SO4. Since the accumulated (NH4)2SO4 can inhibit microbial activity, it is important to utilize an effective sulfur-oxidizing bacterium that has tolerance to high concentrations of (NH4)2SO4 for the simultaneous removal of H2S and NH3. In this study, a sulfur-oxidizing bacterium with tolerance to high concentrations of (NH4)2SO4 was isolated from activated sludge and identified as Acidithiobacillus thiooxidans TAS. A. thiooxidans TAS could display its sulfur-oxidizing activity in a medium supplemented with 60 g.l(-1) (NH4)2SO4, even though its growth and sulfur-oxidizing activity were completely inhibited in 80 g.l(-1) (NH4)2SO4. When H2S alone was supplied to a ceramic biofilter inoculated with A. thiooxidans TAS, an almost 100% H2S removal efficiency was maintained until the inlet H2S concentration was increased up to 900 microl.l(-1) and the space velocity up to 500 h(-1), at which the amount of H2S eliminated was 810 g-S.m(-3).h(-1). However, when NH3 (50-500 microl.l(-1)) was simultaneously supplied to the biofilter with H2S, the maximum amount of H2S eliminated decreased to 650 g-S.m(-3).h(-1). The inhibition of H2S removal by low NH3 concentrations (50-200 microl.l(-1)) was similar to that by high NH3 concentrations (300-500 microl.l(-1)). The critical inlet H2S load that resulted in over 99% removal was determined as 400 g-S.m(-3).h(-1) in the presence of NH3.  (+info)