Effect of fluctuating oxygen concentration on iron oxidation at the pelagic ferrocline of a meromictic lake

2015 ◽  
Vol 12 (6) ◽  
pp. 723 ◽  
Author(s):  
Jenny Bravidor ◽  
Julika Kreling ◽  
Andreas Lorke ◽  
Matthias Koschorreck
Keyword(s):  
Oxygen Concentration ◽  
Iron Reduction ◽  
Iron Oxidation ◽  
Meromictic Lake ◽  
Chemical Gradients ◽  
Oxidation Rates ◽  
Ph Dependency ◽  
Biogeochemical Transformations ◽  
Iron Profile ◽  
Physical And Chemical

Environmental context The cycling of iron plays an important role in pelagic boundary zones such as the oxic–anoxic interface where physical and chemical gradients occur. The turnover of iron in this zone depends on oxygen fluctuation and the duration of the fluctuation event. This study increases the understanding of biogeochemical iron transformation in such hotspots. Abstract In stratified iron-rich lakes, the interface between oxic and anoxic water bodies, the oxycline, is accompanied by a steep gradient of dissolved iron, the ferrocline. It is a hotspot of biogeochemical transformations, namely the cycling of iron (Fe). The rate of iron oxidation, both chemical and microbial, depends on pH, iron and oxygen concentration, and microbial activity. We investigated the ferrocline of the meromictic Lake Waldsee to find out how the ferrocline is influenced by fluctuating oxygen concentrations. We measured diurnal fluctuations of Fe2+, O2 and pH along vertical profiles during two campaigns in July and September 2011 as well as rates of iron oxidation in laboratory incubations. The oxygen content of the water column varied both between the campaigns and diurnally. We observed a diurnal intrusion of O2 into the ferrocline. The diurnal signal was visible in the iron profile in July but not in September. Iron oxidation rates determined in the laboratory demonstrate the importance of microbial iron reduction and the strong pH dependency. We related the reaction timescales for iron oxidation to the characteristic timescale of oxygen fluctuations by calculating non-dimensional numbers. This analysis showed that an oxygenation event had to last at least 10h in order to affect the depth and vertical extent of the ferrocline, which was the case in July but not in September. Our results show that the duration of events can be an important parameter regulating biogeochemical interactions in pelagic redoxclines.

Biological iron oxidation-reduction and the effects on sulfur oxidation-reduction, denitrification and poly-P accumulation in an anaerobic-oxic activated sludge

2002 ◽  
Vol 46 (1-2) ◽  
pp. 55-60 ◽  
Author(s):  
R. Yamamoto-Ikemoto ◽  
T. Komori ◽  
S. Matsui
Keyword(s):  
Activated Sludge ◽  
Sulfate Reduction ◽  
Iron Reduction ◽  
Iron Oxidation ◽  
Sulfur Oxidation ◽  
Monod Equation ◽  
Oxidation Rates ◽  
Oxidation Reduction ◽  
Initial Iron ◽  
P Accumulation

Iron oxidation and reduction were examined using the activated sludge from a municipal plant. Iron contents of the activated sludge were 1–2%. Iron oxidation rates were correlated with the initial iron concentrations. Iron reducing rates could be described by the Monod equation. The effects of iron reducing bacteria on sulfate reduction, denitrification and poly-P accumulation were examined. Iron reduction suppressed sulfate reduction by competing with hydrogen produced from protein. Denitrification was outcompeted with iron reduction and sulfate reduction. These phenomena could be explained thermodynamically. Poly-P accumulation was also suppressed by denitrification. The activity of iron reduction was relatively high.

Investigating the Bioleaching of an Arsenic Mine Tailing Using a Mixed Mesophilic Culture

2017 ◽  
Vol 262 ◽  
pp. 668-672 ◽  
Author(s):  
Emmanuel Ngoma ◽  
Kathija Shaik ◽  
Danilo Borja ◽  
Mariette Smart ◽  
Jay Hyun Park ◽  
...  
Keyword(s):  
Iron Oxidation ◽  
Column Experiment ◽  
Packed Bed ◽  
Microbial Colonization ◽  
Post Inoculation ◽  
Initial Inoculum ◽  
South Korean ◽  
Oxidation Rates ◽  
C 30 ◽  
Kinetics Of

The aim of this study was to investigate the microbial colonization and arsenic leaching kinetics of South Korean mine tailings containing arsenopyrite at fixed temperatures (20°C, 30°C and 45°C) and at ramped up temperatures (25 to 45°C, with a 2°C daily increase). The experiments were conducted in a packed bed of inert granite pebbles coated with the tailings material and leached with a mesophilic culture dominated by Acidithiobacillus caldus (56%), a lesser percentage of Leptospirillum ferriphilum (29%) and Archaea (15%), using 1 g/L ferrous-enriched 0K medium. The ramped-up temperature experiment was conducted in triplicate and columns were sacrificed after different leach periods to study the evolution of microbial species dominating the colonization. The leaching performance was evaluated using the arsenic released into solution, the iron oxidation rates, the pH and the redox potential. The microbial speciation of the culture attached to the solids during the leach experiment was determined upon completion of each experiment. A steady arsenic solubilisation of between 94 and 97% was observed among the various column experiment after 88 days post inoculation. Microbial speciation performed following the leaching of the mineral indicated a shift of microbial communities in the columns when compared to the initial inoculum.

scholarly journals Life at the Energetic Edge: Kinetics of Circumneutral Iron Oxidation by Lithotrophic Iron-Oxidizing Bacteria Isolated from the Wetland-Plant Rhizosphere

2002 ◽  
Vol 68 (8) ◽  
pp. 3988-3995 ◽  
Author(s):  
Scott C. Neubauer ◽  
David Emerson ◽  
J. Patrick Megonigal
Keyword(s):  
Iron Oxidation ◽  
Growth Yield ◽  
Chemical Oxidation ◽  
Total Iron ◽  
Cellular Growth ◽  
Live Cells ◽  
Wetland Plant ◽  
Microbial Oxidation ◽  
Total Oxidation ◽  
Oxidation Rates

ABSTRACT Batch cultures of a lithotrophic Fe(II)-oxidizing bacterium, strain BrT, isolated from the rhizosphere of a wetland plant, were grown in bioreactors and used to determine the significance of microbial Fe(II) oxidation at circumneutral pH and to identify abiotic variables that affect the partitioning between microbial oxidation and chemical oxidation. Strain BrT grew only in the presence of an Fe(II) source, with an average doubling time of 25 h. In one set of experiments, Fe(II) oxidation rates were measured before and after the cells were poisoned with sodium azide. These experiments indicated that strain BrT accounted for 18 to 53% of the total iron oxidation, and the average cellular growth yield was 0.70 g of CH2O per mol of Fe(II) oxidized. In a second set of experiments, Fe(II) was constantly added to bioreactors inoculated with live cells, killed cells, or no cells. A statistical model fitted to the experimental data demonstrated that metabolic Fe(II) oxidation accounted for up to 62% of the total oxidation. The total Fe(II) oxidation rates in these experiments were strongly limited by the rate of Fe(II) delivery to the system and were also influenced by O2 and total iron concentrations. Additionally, the model suggested that the microbes inhibited rates of abiotic Fe(II) oxidation, perhaps by binding Fe(II) to bacterial exopolymers. The net effect of strain BrT was to accelerate total oxidation rates by up to 18% compared to rates obtained with cell-free treatments. The results suggest that neutrophilic Fe(II)-oxidizing bacteria may compete for limited O2 in the rhizosphere and therefore influence other wetland biogeochemical cycles.

scholarly journals Efficient Low-pH Iron Removal by a Microbial Iron Oxide Mound Ecosystem at Scalp Level Run

2017 ◽  
Vol 83 (7) ◽  
Author(s):  
Christen L. Grettenberger ◽  
Alexandra R. Pearce ◽  
Kyle J. Bibby ◽  
Daniel S. Jones ◽  
William D. Burgos ◽  
...  
Keyword(s):  
Acid Mine Drainage ◽  
Bacterial Community ◽  
Microbial Communities ◽  
Mine Drainage ◽  
Iron Oxidation ◽  
Cost Effective ◽  
Low Ph ◽  
Content Type ◽  
Oxidation Rates ◽  
Acid Mine

ABSTRACT Acid mine drainage (AMD) is a major environmental problem affecting tens of thousands of kilometers of waterways worldwide. Passive bioremediation of AMD relies on microbial communities to oxidize and remove iron from the system; however, iron oxidation rates in AMD environments are highly variable among sites. At Scalp Level Run (Cambria County, PA), first-order iron oxidation rates are 10 times greater than at other coal-associated iron mounds in the Appalachians. We examined the bacterial community at Scalp Level Run to determine whether a unique community is responsible for the rapid iron oxidation rate. Despite strong geochemical gradients, including a >10-fold change in the concentration of ferrous iron from 57.3 mg/liter at the emergence to 2.5 mg/liter at the base of the coal tailings pile, the bacterial community composition was nearly constant with distance from the spring outflow. Scalp Level Run contains many of the same taxa present in other AMD sites, but the community is dominated by two strains of Ferrovum myxofaciens, a species that is associated with high rates of Fe(II) oxidation in laboratory studies. IMPORTANCE Acid mine drainage pollutes more than 19,300 km of rivers and streams and 72,000 ha of lakes worldwide. Remediation is frequently ineffective and costly, upwards of $100 billion globally and nearly $5 billion in Pennsylvania alone. Microbial Fe(II) oxidation is more efficient than abiotic Fe(II) oxidation at low pH (P. C. Singer and W. Stumm, Science 167:1121–1123, 1970, https://doi.org/10.1126/science.167.3921.1121 ). Therefore, AMD bioremediation could harness microbial Fe(II) oxidation to fuel more-cost-effective treatments. Advances will require a deeper understanding of the ecology of Fe(II)-oxidizing microbial communities and the factors that control their distribution and rates of Fe(II) oxidation. We investigated bacterial communities that inhabit an AMD site with rapid Fe(II) oxidation and found that they were dominated by two operational taxonomic units (OTUs) of Ferrovum myxofaciens, a taxon associated with high laboratory rates of iron oxidation. This research represents a step forward in identifying taxa that can be used to enhance cost-effective AMD bioremediation.

A Novel Apparatus to Determine the Bio-Oxidation Kinetics of Sessile Leptospirillum ferriphilum

2013 ◽  
Vol 825 ◽  
pp. 238-241 ◽  
Author(s):  
Porogo Duku ◽  
Sanet H. Minnaar ◽  
Susan T.L. Harrison ◽  
Jochen Petersen
Keyword(s):  
Oxidation Kinetics ◽  
Iron Oxidation ◽  
Packed Bed ◽  
Leptospirillum Ferriphilum ◽  
Oxidation Rates ◽  
Cell Counts ◽  
Ferrous Iron Oxidation ◽  
Uptake Rates ◽  
Carbon Utilisation ◽  
Kinetics Of

A novel apparatus was developed to test the ferrous iron oxidation kinetics of Leptospirillum ferriphilum in predominantly sessile culture, by combining a CSTR under wash-out conditions with a packed bed of inert ceramic saddles. Results indicate that a dense culture of sessile bacteria is established rapidly, which achieves high oxidation rates in all experiments with a yield in terms of CO2 uptake rates comparable or higher to what has been measured in planktonic culture. However, the yield in terms of cell counts changes dramatically, indicating a substantial shift in carbon utilisation in the sessile culture. The apparatus is feasible as a method to study iron oxidation kinetics of sessile cultures, providing it is operated at sufficiently high recycle ratios.

Oxygen and carbon dioxide kinetic challenges for thermophilic mineral bioleaching processes

2004 ◽  
Vol 32 (2) ◽  
pp. 273-275 ◽  
Author(s):  
S.H. de Kock ◽  
P. Barnard ◽  
C.A. du Plessis
Keyword(s):  
Ferrous Iron ◽  
Large Scale ◽  
Elevated Temperatures ◽  
Ferrous Sulphate ◽  
Iron Oxidation ◽  
Co2 Concentration ◽  
Batch Cultures ◽  
Oxidation Rates ◽  
Ferrous Iron Oxidation ◽  
Oxygen Gas

Agitated bacterial tank bioleaching reactors are currently sparged with air to satisfy both oxygen and CO2 requirements of microbial cells. Under high-sulphide loading conditions, as is the case with high-grade metal sulphide concentrates, the microbial and chemical demand for oxygen is significantly increased during the bioleaching process. Sparging with enriched oxygen gas may offer an alternative process option to increased agitation and sparged aeration, to overcome the mass transfer difficulties at elevated temperatures where thermophilic Archaea, rather than Bacteria, are used. In the case of air sparging, the DO (dissolved oxygen) concentration in tank reactors could not be increased to a point where it would become inhibitory due to the limited oxygen content of air (20.9% O2). The use of enriched oxygen in such reactors at large scale does, however, pose its own set of process risks. The first aim of this investigation was, therefore, to determine the effects of various DO concentrations, in both the limiting and inhibitory ranges, on the microbial activity of Sulfolobus sp. U40813, a typical thermophilic mineral-leaching archaeon. Secondly, the effect of CO2 concentration on the rate of ferrous iron oxidation was investigated. Both the oxygen and CO2 kinetics were examined in controlled batch cultures at 78°C, using ferrous sulphate and potassium tetrathionate as energy sources. The optimal DO concentration for iron oxidation was found to be between 1.5 and 4.1 mg·l−1. The use of elevated DO concentrations (above 4.1 mg·l−1) inhibited the ferrous oxidation rates. The optimal gas CO2 concentration for ferrous iron oxidation was found to be in the range 7–17% (v/v). The iron oxidation rates were, however, severely limited at CO2 concentrations less than 7%, indicating that the CO2 supply was limiting in this range and inhibited the microbial growth rate.

Responses of microorganisms to physical and chemical gradients

1982 ◽  
Vol 297 (1088) ◽  
pp. 497-515 ◽  
Keyword(s):  
Numerical Models ◽  
Biologically Active ◽  
Model Systems ◽  
Natural Ecosystems ◽  
Bacterial Colony ◽  
Chemical Gradients ◽  
Constant Dimension ◽  
Heterogeneous Structures ◽  
Agar Layer ◽  
Physical And Chemical

Most microbial ecosystems are spatially organized heterogeneous structures where microbes proliferate in gradients of biologically active solute molecules as well as in physical gradients of temperature, pressure, light, ionic strength, redox potential, pH and so on. Some of these ecosystems are discussed in this paper; however, the importance of investigating them in the laboratory is stressed. My group has developed a number of model systems. Seven of these are discussed and include four experimental, two numerical and one conceptual models. These are briefly described. (1) The gradostat consists of a number of bidirectionally linked fermenter vessels fed with solutes from each end of the array. Steady-state solute counter-gradients are established. A number of results in which different microbes are grown in different gradient systems are described. (2) The gel-stabilized system: organisms are grown in a solute gradient diffusing from a source agar layer beneath a semisolid layer containing agar and cells. (3) A constant dimension thin film fermenter. (4) The bacterial colony. (5, 6) The two numerical models, devised to simulate growth in the gradostat and in gel-stabilized systems respectively. (7) A conceptual model in which cells are regarded as compartments surrounded by activity domains; the importance of vectorial solute transfer in natural ecosystems is stressed.

scholarly journals Chemotaxis and topotaxis add vectorially for amoeboid cell migration

2019 ◽  
Author(s):  
Joeri A. J. Wondergem ◽  
Maria Mytiliniou ◽  
Falko C. H. de Wit ◽  
Thom G. A. Reuvers ◽  
David Holcman ◽  
...  
Keyword(s):  
Cell Migration ◽  
Chemical Cues ◽  
Effective Diffusion ◽  
Diffusion Constant ◽  
Emergent Property ◽  
Coarse Grained ◽  
Chemical Gradients ◽  
Amoeboid Cell ◽  
Physical And Chemical ◽  
Chemotactic Gradient

AbstractCells encounter a wide variety of physical and chemical cues when navigating their native environments. However, their response to multiple simultaneous cues is not yet clear. In particular, the influence of topography, in the presence of a chemotactic gradient, on their migratory behavior is understudied. Here, we investigate the effects of topographical guidance on highly motile amoeboid cell migration (topotaxis) generated by asymmetrically placed micropillars. The micropillar field allows for an additional, natural chemotactic gradient in two different directions, thereby revealing the relevance of topotaxis in the presence of cell migration directed by chemical gradients (chemotaxis). Interestingly, we found that the topotactic drift generated by the pillar field is conserved during chemotaxis. We show that the drifts generated by both these cues add up linearly. A coarse-grained analysis as a function of pillar spacing subsequently revealed that the strength and direction of the topotactic drift is determined by (i) the pore size, (ii) space between pores, and (iii) the effective diffusion constant of the cells. Finally, we argue that topotaxis must be conserved during chemotaxis, as it is an emergent property of both the asymmetric properties of the pillar field and the inherent stochasticity of (biased) amoeboid migration.

scholarly journals Microbial subnetworks related to short-term diel O2fluxes within geochemically distinct freshwater wetlands

2018 ◽  
Author(s):  
Dean J. Horton ◽  
Matthew J. Cooper ◽  
Anthony J. Wing ◽  
Peter S. Kourtev ◽  
Donald G. Uzarski ◽  
...  
Keyword(s):  
Community Structure ◽  
Microbial Community ◽  
Microbial Communities ◽  
Archaeal Community ◽  
Freshwater Wetlands ◽  
Freshwater Wetland ◽  
Short Term ◽  
Wetland Ecosystems ◽  
Biogeochemical Transformations ◽  
Physical And Chemical

ABSTRACTO2concentrations often fluctuate over diel timescales within wetlands, driven by temperature, sunlight, photosynthesis, and respiration. These daily fluxes have been shown to impact biogeochemical transformations (e.g. denitrification), which are mediated by the residing microbial community. However, little is known about how resident microbial communities respond to diel dramatic physical and chemical fluxes in freshwater wetland ecosystems. In this study, total microbial (bacterial and archaeal) community structure was significantly related to diel time points in just one out of four distinct freshwater wetlands sampled. This suggests that daily environmental shifts may influence wetlands differentially based upon the resident microbial community and specific physical and chemical conditions of a freshwater wetland. However, when exploring at finer resolutions of the microbial communities within each wetland, subcommunities within two wetlands were found to correspond to fluctuating O2levels. Microbial taxa that were found to be susceptible to fluctuating O2levels within these subnetworks may have intimate ties to metabolism and/or diel redox cycles. This study highlights that freshwater wetland microbial communities are often stable in community structure when confronted with short-term O2fluxes, however, specialist taxa may be sensitive to these same fluxes.

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