Utilization of Nitrite as a Nitrogen Source by Botryococcus Braunii

Nitrite at 2 mM did not affect the growth of Botryococcus braunii and served as the sole nitrogen source giving a minimum biomass doubling time of 4.2 d, which was equal to that of the culture using 4 mM nitrate as nitrogen source. With nitrite at 4 mM, after a lag phase of about 10 d, the alga grew quickly, reaching 1.1 g l(-1) at the end. Respective nitrite removals were 100% and 99.7%. There were few differences in the hydrocarbons produced using different nitrogen sources.     

Genetics of the Synthesis of Serine from Glycine and the Utilization of Glycine as Sole Nitrogen Source by Saccharomyces Cerevisiae

Saccharomyces cerevisiae can grow on glycine as sole nitrogen source and can convert glycine to serine via the reaction catalyzed by the glycine decarboxylase multienzyme complex (GDC). Yeast strains with mutations in the single gene for lipoamide dehydrogenase (lpd1) lack GDC activity, as well as the other three 2-oxoacid dehydrogenases dependent on this enzyme. The LPD1 gene product is also required for cells to utilize glycine as sole nitrogen source. The effect of mutations in LPD1 (L-subunit of GDC), SER1 (synthesis of serine from 3-phosphoglycerate), ADE3 (cytoplasmic synthesis of one-carbon units for the serine synthesis from glycine), and all combinations of each has been determined. The results were used to devise methods for isolating mutants affected either in the generation of one-carbon units from glycine (via GDC) or subsequent steps in serine biosynthesis. The mutants fell into six complementation groups (gsd1-6 for defects in conversion of glycine to serine). Representatives from three complementation groups were also unable to grow on glycine as sole nitrogen source (gsd1-3). Assays of the rate of glycine uptake and decarboxylation have provided insights into the nature of the mutations.     

Biosorption of Cu by Thiobacillus ferrooxidans

Current technologies for removal and recovery of both toxic and industrial interest metals usually produce wastes with high concentrations of those substances. They are an important source of environmental pollution, specially when they contain heavy metals. This is one of the most important environmental problems, and of the most difficult to solve. So far, there have been a number of studies considering the possibility of removing and recovering heavy metals from diluted solutions. These are due, principally, because of the commercial value of some metals as well as the environmental impact caused by them. The traditional methods for removing have several disadvantages when metals are present in concentrations lower than 100?mg/l. Biosorption, which uses biological materials as adsorbents, has been considered as an alternative method. In this work, several variables that affect the capacity for copper biosorption by T. ferrooxidans have been studied. Particularly, the effect of pH, chemical pretreatment, biomass concentration and temperature have been considered. Results indicate that a capacity as high as 119?mg of Cu/g of dry biomass can be obtained at a temperature of 25?°C.     

Reduction of dichromate by Thiobacillus ferrooxidans

Chromium(VI) was reduced by Thiobacillus ferrooxidans grown with elemental sulphur as the sole energy source. Chromium(VI) reduction (as high as 2000 M), was due to the presence of sulphite and thiosulphate, among others with high reducing power which was generated during the sulphur oxidation by the bacteria. Therefore, Thiobacillus ferrooxidans could be used to treat chromium(VI)-containing industrial effluents.     

Utilization of Anhydrous Aluminum Phosphate as a Sole Source of Phosphorous by a Selected Carrot Cell Line

Two variants of carrot (Daucus carota L. cv. MS Yonsun) celllines, which had been selected with Al-phosphate as a sole sourceof phosphorous, were characterized on their mechanisms of phosphate-utilizationfrom Al-phosphate. Both cell lines excreted citrate into themedium. The amount of citrate excretion was highly correlatedwith cell growth in the presence of Al-phosphate. There wasabout a 1 to 1 correlation between solublized-Al and excreted-citratein the medium during cell growth. These results suggest that1) the citrate could chelate with Al, at a 1 to 1 ratio, inAl-phosphate, 2) the citrate-chelated Al remains outside thecells, and 3) solublized phosphate from Al-phosphate is utilizedfor the growth of carrot cells. The characteristics of the selectedcells were very stable, since the rate of citrate-excretionshowed no change after subculturing 25 passages without Al-phosphate. (Received August 7, 1989; Accepted October 19, 1989)     

氧化亚铁硫杆菌的形态及对Fe2+的氧化研究

在纯培养的条件下,对江西德兴铜矿酸性矿坑水中分离出的一株氧化亚铁硫杆菌(Thiobacillus ferrooxidans)的细胞形态、生长条件以及对Fe2 的氧化进行了初步研究。透射电子显微镜检查的结果表明,其成熟菌体大小均一,有较好的运动性;采用光学显微镜对微生物进行菌群观测和利用血小板计数器法对细菌计数的结果表明,在摇床转速为160r/min的条件下,T.f.菌在9K液体培养基中最适生长条件为温度30℃左右,最佳初始pH 2.0;用重铬酸钾滴定法测定铁的结果表明,在摇床转速为160r/min的条件下,pH值1.7,温度30℃时T.f.菌对Fe2 的氧化速率最大,约为0.58g/L·h。     

Microbiological leaching of a chalcopyrite concentrate by Thiobacillus ferrooxidans

The microbiological leaching of a chalcopyrite concentrate has been investigated using a pure strain of Thiobacillus ferrooxidans. The optimum leaching conditions regarding pH, temperature, and pulp density were found to be 2.3, 35°C, and 22%, respectively. The energy of activation was calculated to be 16.7 kcal/mol. During these experiments the maximum rate of copper dissolution was about 215 mg/liters/hr and the final copper concentration was as high as 55 g/liter. This latter value is in the range of copper concentrations which may be used for direct electrorecovery of copper. Jarosite formation was observed during the leaching of the chalcopyrite concentrate. When the leach residue was reground to expose new substrate surface, subsequent leaching resulted in copper extractions up to about 80%. On the basis of this experimental work, a flow sheet has been proposed for commercial scale biohydrometallurgical treatment of high-grade chalcopyrite materials.     

Combined degradation of covellite by Thiobacillus thiooxidans and Thiobacillus ferrooxidans

Summary In the presence of iron, which is always associated with natural sulphide ores, the percentages of copper dissolution in the bioleaching of covellite were 34 and 45 % when Thiobacillus thiooxidans and Thiobacillus ferrooxidans were used together and when an indirect bioleaching with attached bacteria was performed respectively. In the latter, the percentage of copper dissolution was still higher than the percentages obtained with pure cultures (36 % with a T. thiooxidans culture and 40 % with a T. ferrooxidans culture).     

New Insight into Microbial Iron Oxidation as Revealed by the Proteomic Profile of an Obligate Iron-Oxidizing Chemolithoautotroph

Microaerophilic, neutrophilic, iron-oxidizing bacteria (FeOB) grow via the oxidation of reduced Fe(II) at or near neutral pH, in the presence of oxygen, making them relevant in numerous environments with elevated Fe(II) concentrations. However, the biochemical mechanisms for Fe(II) oxidation by these neutrophilic FeOB are unknown, and genetic markers for this process are unavailable. In the ocean, microaerophilic microorganisms in the genus Mariprofundus of the class Zetaproteobacteria are the only organisms known to chemolithoautotrophically oxidize Fe and concurrently biomineralize it in the form of twisted stalks of iron oxyhydroxides. The aim of this study was to identify highly expressed proteins associated with the electron transport chain of microaerophilic, neutrophilic FeOB. To this end, Mariprofundus ferrooxydans PV-1 was cultivated, and its proteins were extracted, assayed for redox activity, and analyzed via liquid chromatography-tandem mass spectrometry for identification of peptides. The results indicate that a cytochrome c₄, cbb₃-type cytochrome oxidase subunits, and an outer membrane cytochrome c were among the most highly expressed proteins and suggest an involvement in the process of aerobic, neutrophilic bacterial Fe oxidation. Proteins associated with alternative complex III, phosphate transport, carbon fixation, and biofilm formation were abundant, consistent with the lifestyle of Mariprofundus.     

Bacterial dissolution of pyrite by Thiobacillus ferrooxidans

The kinetics of the dissolution of pure pyrite (FeS₂) particles by Thiobacillus ferrooxidans were studied both theoretically and experimentally. Adsorption and dissolution experiments were carried out at 30 °C and pH=2, by using a batch reactor. The adsorption process of T. ferrooxidans to pyrite surface was rapid in comparison with the bacterial dissolution process. The experimental results for the adsorption equilibrium were well correlated by the Langmuir type isotherm. The growth rate of adsorbed bacteria was found to be proportional to the product of the number of adsorbed cells and the fraction of solid surface unoccupied by cells. A new kinetic model for the bacterial dissolution was presented, and shown to correlate well with the experimental data for the rate of bacterial dissolution and for the time variation in the number of cells in the liquid phase. The specific growth rate of adsorbed bacteria was also evaluated.List of Symbols f weight fraction of iron in pyrite - K _A m³/cells equilibrium constant for cell adsorption - R _A cells/d m³-mixture growth rate of bacteria adsorbed on solid surface - R _L cells/d m³-mixture growth rate of free bacteria in the liquid phase - t d time - V m³ volume of solid-liquid mixture - W kg weight of pyrite - W ₀ kg initial weight of pyrite - X _A cells/kg-solid number of adsorbed cells on solid surface - X _Am cells/kg-solid maximum adsorption capacity - X _L cells/m³-liquid number of free cells existing in the liquid phase - X _T cells/m³-mixture total number of cells - X _TO cells/m³ initial total number of cells - Y _A cells/kg-FeS₂ growth yield of adsorbed bacteria - Y _L cells/kg-Fe²⁺ growth yield of free bacteria - [Fe] _T kg/m³-liquid concentration of total iron in the liquid phase - fraction of pyrite dissolved - _V fraction of adsorption sites unoccupied by cells - _A d^–1 specific growth rate of adsorbed bacteria - _L d^–1 specific growth rate of free bacteria - volume fraction of solid particles in solid-liquid mixture     

Surface sulphur as promoting agent of pyrite leaching by Thiobacillus ferrooxidans

Abstract: Methanol extraction conducted with a HPLC-Iike device and spectroscopic analysis were used to remove and characterize the sulphur layer (Ss) present on freshly ground pyrite surface after dry grinding. Accurate measurements of ferric and sulphate contents in the leachate showed a significant delay in the lag phase and in the first step of oxidation by Thiobacillus ferrooxidans for the so-cleaned pyrite (without sulphur layer) in comparison to the initial pyrite (with sulphur layer). Voltammetric studies (current-potential curves) showed a modification of the anodic behaviour of the initial pyrite, corresponding to a higher chemical oxidability of the uncleaned pyrite. During the bacterial oxidation, the difference in redox potential between a special pyrite electrode and a platinum standard electrode both placed in the bioleaching reactor was shown to be related to the occurrence of a sulphur layer. This difference, which is more important in the case of the initial pyrite (with sulphur layer), corresponded to an increase in oxidation kinetics of the pyrite by Thiobacillus ferrooxidans .     

Amino acid sequence of the blue copper protein rusticyanin from Thiobacillus ferrooxidans

Rusticyanin is a small blue copper protein isolated from Thiobacillus ferrooxidans. The amino acid sequence of the rusticyanin has been determined by the structural characterization of tryptic and endoproteinase Asp-N peptides with use of amino terminal microsequencing, fast atom bombardment mass spectrometry, and electrospray triple-quadrupole mass spectrometry techniques. Amino acid analysis, carboxy-terminal sequence analysis, and circular dichroism spectroscopy were also performed on the protein. Amino acid sequence identity among rusticyanin and six other small blue copper proteins is apparent only in the limited C-terminal region of each protein bearing three of the four putative copper ligands. A structural model of the rusticyanin is proposed where the protein is principally a beta-barrel comprised of six strands. This model is consistent with the circular dichroism data and computational predictions of the secondary structure of rusticyanin. A feature of the model is the hypothesis that Asp 73 may serve as a fourth copper ligand.     

Kinetics of Iron Oxidation by Thiobacillus ferrooxidans

A statistical relationship between the rate of ferric ion production by a strain of Thiobacillus ferrooxidans and various levels of cell concentration, Fe²⁺ concentration, Na⁺ concentration, and temperature was studied by a direct colorimetric method at 304 nm. The relationship was linear (90 to 93%), cross-product (3 to 4%), and quadratic (1 to 2%). The levels of cell concentration and Fe²⁺ concentration and their respective interactions with one another and the other factors had the most significant effects on the regression models. The solution of the quadratic response surface for optimum oxidation was a saddle point, and the predicted critical levels of temperature, cell concentration, Fe²⁺ concentration, and Na⁺ concentration ranged between −6 and 2°C, 0.43 and 0.62 mg/ml, 72 and 233 mM, and 29.6 mM, respectively.     

Anaerobic leaching of covellite by Thiobacillus ferrooxidans

Thiobacillus ferrooxidans was able to grow under anaerobic conditions on copper sulphide with ferric ion as the electron acceptor. The dissolution of covellite under these conditions (68% after 35 days) was higher than values observed aerobically in cultures with similar media composition and almost as high as under aerobic conditions without iron. From these results we propose a mechanism for anaerobic bioleaching of covellite in the presence of ferric iron and speculate that it may occur in leach dumps where the oxygen concentration is, as reported elsewhere, very low. Received: 3 September 1996 / Received revision: 13 January 1997 / Accepted: 24 January 1997     

Oxidation of arsenopyrite by Thiobacillus ferrooxidans detected by a mineral electrode

Summary A new electrochemical study of arsenopyrite biooxidation was based on process detection by arsenopyrite electrode. The rate of reaction was evaluated as the exchange current density calculated from polarization curves. Obtained data were used for determination of released electrons from mineral and for evaluation of reaction mechanism of its oxidation.     

Utilization of γ-Aminobutyric Acid as the Sole Carbon and Nitrogen Source by Escherichia coli K-12 Mutants

Wild-type strains of Escherichia coli K-12 cannot grow in media with gamma-aminobutyrate (GABA) as the sole source of carbon or nitrogen. Mutants were isolated which could utilize GABA as the sole source of nitrogen. These mutants were found to have six- to ninefold higher activities of gamma-aminobutyrate-alpha-ketoglutarate transaminase (EC 2.6.1.19) and succinate semialdehyde dehydrogenase (EC 1.2.1.16) than those of the wild-type parent strains. Secondary mutants derived from these GABA-nitrogen-utilizing strains were able to grow on GABA as the sole source of carbon and nitrogen. They also grew faster on a variety of other carbon and nitrogen sources, and their growth was more strongly inhibited by different metabolic inhibitors than was that of the parent strains. The nature of the two mutations and the possible genes involved are discussed. A scheme of the pathway for GABA breakdown in E. coli K-12 is presented.     

Corrosion and Electrochemical Oxidation of a Pyrite by Thiobacillus ferrooxidans

The oxidation of a pure pyrite by Thiobacillus ferrooxidans is not really a constant phenomenon; it must be considered to be more like a succession of different steps which need characterization. Electrochemical studies using a combination of a platinum electrode and a specific pyrite electrode (packed-ground-pyrite electrode) revealed four steps in the bioleaching process. Each step can be identified by the electrochemical behavior (redox potentials) of pyrite, which in turn can be related to chemical (leachate content), bacterial (growth), and physical (corrosion patterns) parameters of the leaching process. A comparison of the oxidation rates of iron and sulfur indicated the nonstoichiometric bacterial oxidation of a pure pyrite in which superficial phenomena, aqueous oxidation, and deep crystal dissolution are successively involved.