Iron Oxidation and Precipitation of Ferric Hydroxysulfates by Resting Thiobacillus ferrooxidans Cells

The oxidation of ferrous ions, in acid solution, by resting suspensions of Thiobacillus ferrooxidans produced sediments consisting of crystalline jarosites, amorphous ferric hydroxysulfates, or both. These products differed conspicuously in chemical composition and infrared spectra from precipitates formed by abiotic oxidation under similar conditions. The amorphous sediments, produced by bacterial oxidation, exhibited a distinctive fibroporous microstructure when examined by scanning electron microscopy. Infrared spectra indicated outer-sphere coordination of Fe(III) by sulfate ions, as well as inner-sphere coordination by water molecules and bridging hydroxo groups. In the presence of excess sulfate and appropriate monovalent cations, jarosites, instead of amorphous ferric hydroxysulfates, precipitated from bacterially oxidized iron solutions. It is proposed that the jarositic precipitates result from the conversion of outer-sphere (T(d)) sulfate, present in a soluble polymeric Fe(III) complex, to inner-sphere (C(3v)) bridging sulfate. The amorphous precipitates result from the further polymerization of hydroxo-linked iron octahedra and charge stabilized aggregation of the resulting iron complexes in solution. This view was supported by observations that bacterially oxidized iron solutions gave rise to either amorphous or jarositic sediments in response to ionic environments imposed after oxidation had been completed and the bacteria had been removed by filtration.

SULFATE REQUIREMENT FOR IRON OXIDATION BY THIOBACILLUS FERROOXIDANS

Lazaroff, Norman (British Columbia Research Council, Vancouver, B.C., Canada). Sulfate requirement for iron oxidation by Thiobacillus ferrooxidans. J. Bacteriol. 85:78-83. 1963.-The growth of Thiobacillus ferrooxidans is initially inhibited in media containing ferrous chloride in place of ferrous sulfate. This inhibition of growth is due to the requirement of a high relative proportion of sulfate ions to chloride (or other anions) for iron oxidation. Adaptation takes place, producing strains which are able to oxidize iron in media containing an initially unfavorable anionic composition. Adaptation is possibly due to the selection of spontaneous mutants capable of oxidizing iron in high chloride, low sulfate media. Such cells are found at a frequency of 10(-5) of the population of unadapted cultures.

Sulfate-dependent iron oxidation by Thiobacillus ferrooxidans: characterization of a new EPR detectable electron transport component on the reducing side of rusticyanin

Iron(II) oxidation by pH 2.5 HCl-washed cells of Thiobacillus ferrooxidans is known to be sulfate dependent. Sulfate dependence of the autooxidation of a novel component in the electron transport pathway is demonstrated. This component exhibits an electron paramagnetic resonance (EPR) signal in the oxidized state at g = 2.005 distinguishable from the g = 2.08 signal attributed to rusticyanin. The novel component is proposed to be a three-iron-sulfur cluster based upon the g value, lineshape, and temperature dependence. Oxyanion specificity for the EPR signal has the same dependence on sulfate as does iron(II) oxidation. By using azide to inhibit electron transfer to oxygen, sulfate was shown to be involved in electron transfer from the g = 2.005 component to the copper of rusticyanin.

The Exclusion of D 2 O from the Hydration Sphere of FeSO 4 · 7H 2 O Oxidized by Thiobacillus ferrooxidans

Infrared spectra demonstrate that neither FeSO(4) . 7H(2)O nor its bacterial or abiotic hydrated oxidation products incorporate deuterium in acid D(2)O solutions. Deuterium exchange occurred as bridging OD when bacterially oxidized iron was precipitated from D(2)O solutions as ferric hydroxysulfates. The exclusion of deuterium depended upon the stabilization of aquated Fe(II) and Fe(III) complexes by sulfate ions in outer-sphere coordination and is consistent with the requirement and postulated role of sulfate in iron oxidation by Thiobacillus ferrooxidans.

Direct method for continuous determination of iron oxidation by autotrophic bacteria

A method for direct, continuous determination of ferric ions produced in autotrophic iron oxidation, which depends upon the measurement of ferric ion absorbance at 304 nm, is described. The use of initial rates is shown to compensate for such changes in extinction during oxidation, which are due to dependence of the extinction coefficient on the ratio of complexing anions to ferric ions. A graphical method and a computer method are given for determination of absolute ferric ion concentration, at any time interval, in reaction mixtures containing Thiobacillus ferrooxidans and ferrous ions at known levels of SO(4) (2+) and hydrogen ion concentrations. Some examples are discussed of the applicability of these methods to study of the rates of ferrous ion oxidation related to sulfate concentration.

PHOTOINDUCTION AND PHOTOREVERSAL OF THE NOSTOCACEAN DEVELOPMENTAL CYCLE(1)

The developmental cycle of Nostoc muscorum, a nitrogen-fixing blue-green alga, is controlled by the spectral quality of illumination. Red light with peak activity at 650 mμ induces development of filaments from a nonfilamentous (aseriate) stage of the life cycle. Red-light photoinduction is reversed by simultaneous or subsequent exposure to light from a broad band in the green region of the spectrum. Photo-reversibility of the red-light induction, by green light, decays very slowly, remaining at an appreciable level for over 24 hr after the primary stimulus. Allophycocyanin is indicated to be the photoreceptor for red-light induction. One or more phyco-erythrins may operate as photoreceptors for reversal of induction. The dosage response and wavelength dependence of developmental photocontrol in Nostoc muscorum A indicate that a nonphotosynthetic mechanism is involved in both developmental photoinduction and its photor ever sal.

Calcium and Magnesium Uptake by Barley Seedlings

Measurements have been made of calcium and magnesium uptake to barley seedlings (Hordeum vulgare) growing on nutrient solutions. Uptake to the shoot increased with solution concentration and showed a preference for magnesium, largely due to the action of transpiration. Though uptake of both ions was increased by higher transpiration, magnesium was more affected than was calcium. In the root, calcium was taken up preferentially to magnesium, and the levels were not affected by transpiration rate.

Action Spectrum for Developmental Photo-Induction of the Blue-Green Alga Nostoc muscorum

The dark-grown cyanophyte requires a brief exposure to light from the 650 mmicro region of the spectrum before it can complete its developmental cycle. Induction is reversed by exposure to green light. A blue protein, presumably allophycocyanin (absorption maximum, 650 mmicro) has been demonstrated in aqueous extracts of the cyanophycean cells.