Stratification of microbial metabolic processes and redox potential change in an aerobic biofilm studied using microelectrodes

In this study, we examined the stratification of microbial processes and the associated redox potential changes in biofilms using microelectrode techniques. Two types of biofilms, each with a different combination of microbial processes, were examined. The first type carried aerobic oxidation and sulfate reduction, while the second one provided aerobic oxidation and nitrification. The microelectrodes used were oxygen, sulfide, ammonium, pH and redox potential microelectrodes. The results of this study provide the following new experimental evidence: (1) The aerobic/sulfate-reducing biofilm had a clearly stratified structure with depth. In this biofilm, aerobic oxidation took place only in a shallow layer near the surface and sulfate reduction occurred in the deeper anoxic zone. The boundary between these two processes was well defined. (2) The aerobic/nitrifying biofilm also had a stratified structure with depth. In this biofilm, though aerobic oxidation took place throughout the biofilm depth, more nitrification occurred in the deeper section of the biofilm. The boundary between these two processes, however, was less well defined. (3) Redox potential could be an indicator for the existence of certain microbial processes in biofilms. The redox potential profile changes were correlated to shifts of microbial processes in both types of biofilms. The redox potential profiles in these biofilms can be used to elucidate the stratification of microbial processes in the biofilms.

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Exploring Coupled Redox and pH Processes with a Force Field-Based Approach: Applications to Five Different Systems

10.26434/chemrxiv.11782188.v1 ◽

2020 ◽

Author(s):

Vinicius Cruzeiro ◽

Gustavo Troiano Feliciano ◽

Adrian Roitberg

Keyword(s):

Force Field ◽

Redox Potential ◽

Desulfovibrio Vulgaris ◽

Cytochrome C3 ◽

Computational Tools ◽

Redox States ◽

Computational Performance ◽

Redox Active ◽

Constant Ph ◽

Experimental Findings

Coupled redox and pH-driven processes are at the core of many important biological mechanisms. As the distribution of protonation and redox states in a system is associated with the pH and redox potential of the solution, having efficient computational tools that can simulate under these conditions become very important. Such tools have the potential to provide information that complement and drive experiments. In previous publications we have presented the implementation of the constant pH and redox potential molecular dynamics (C(pH,E)MD) method in AMBER and we have shown how multidimensional replica exchange can be used to significantly enhance the convergence efficiency of our simulations. In the current work, after an improvement in our C(pH,E)MD approach that allows a given residue to be simultaneously pH- and redox-active, we have employed our methodologies to study five different systems of interest in the literature. We present results for: capped tyrosine dipeptide, two maquette systems containing one pH- and redox-active tyrosine (α3Y and peptide A), and two proteins that contain multiple heme groups (diheme cytochrome c from Rhodobacter sphaeroides and Desulfovibrio vulgaris Hildenborough cytochrome c3). We show that our results can provide new insights into previous theoretical and experimental findings by using a fully force field-based and GPUaccelerated approach, which allows the simulations to be executed with high computational performance.

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Anaerobic Filter Treatment of Sulfate-Containing Wastewaters

Water Science & Technology ◽

10.2166/wst.1991.0580 ◽

1991 ◽

Vol 23 (7-9) ◽

pp. 1283-1291 ◽

Cited By ~ 19

Author(s):

G. F. Parkin ◽

M. A. Sneve ◽

H. Loos

Keyword(s):

Sulfate Reduction ◽

Biological Processes ◽

Organic Loading ◽

Potential Toxicity ◽

Industrial Wastewaters ◽

Loading Rates ◽

Anaerobic Filter ◽

Sulfate Reducing ◽

Dissolved Sulfide ◽

Reducing Bacteria

The use of anaerobic biological processes for the treatment of industrial wastewaters has significant merit. When high levels of sulfate are present, the sulfate is biologically reduced to sulfide, the result being potential toxicity to the consortia of organisms responsible for producing methane. An upflow anaerobic filter-fed propionate as a substrate was used to study the interaction between sulfate-reducing bacteria and methane-producing bacteria. Hydraulic retention times of one and two days were used, organic loading rates were varied from 3 to 5 g COD/L-day, and feed COD/S ratios were varied from 20/1 to 8/1. Unionized hydrogen sulfide and dissolved sulfide levels associated with decreased process performance were approximately 110 mg S/L and 350 mg S/L, respectively. These levels are significantly higher than those levels causing inhibition in completely mixed-reactors. Most of the sulfate reduction and propionate removal took place in the first 300 mm of the 1050-mm-long reactor, indicating that sulfate reduction and methane production were occurring in the sane location in the filter.

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Influence of Container Base Material (Fe) on SIMFUEL Leaching Behavior

MRS Proceedings ◽

10.1557/proc-663-435 ◽

2000 ◽

Vol 663 ◽

Cited By ~ 2

Author(s):

J. Quiñones ◽

J.A. Serrano ◽

P.P. Díaz ◽

J.L. Rodríguez Almazán ◽

J. Cobos ◽

...

Keyword(s):

Experimental Data ◽

Redox Potential ◽

Uranium Concentration ◽

Near Field ◽

Base Material ◽

Fission Products ◽

Sharp Decrease ◽

Spent Fuel ◽

Leaching Behavior ◽

Redox Sensitivity

ABSTRACTThe chemical stability of spent fuel will be greatly influenced by the redox potential of the near field. Presence of reductants such as iron is likely to be an important factor to maintain the original integrity of spent fuel. In this work experimental data about the influence of metallic iron (container base material) on SIMFUEL leaching behavior under simulated granite and saline repository conditions is presented. In the presence of iron uranium concentration undergoes a sharp decrease. This is much more noticeable in the experiments performed under initial oxic conditions. The effect of iron on simulated fission products of SIMFUEL is very important for the elements with high redox sensitivity such us molybdenum. On the contrary, strontium remains stable during the entire tests and it seems not be affected by changes in redox potential.

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Review: Formation and Metabolic Function of Coral Rubble Biofilms in the Reef Ecosystem

Gulf and Caribbean Research ◽

10.18785/gcr.3201.07 ◽

2021 ◽

Vol 32 ◽

pp. 46-56

Author(s):

Andres Sanchez-Quinto ◽

Luisa Falcon

Keyword(s):

Nitrogen Fixation ◽

Coral Reefs ◽

Sulfate Reduction ◽

Sulfide Oxidation ◽

Taxonomic Composition ◽

Coralline Algae ◽

Metabolic Processes ◽

Coral Rubble ◽

Functional Roles ◽

Healthy Coral

When coral dies, their calcareous skeletons constitute coral rubble in conjunction with the cementing activity of coralline algae and bacteria, creating a secondary reef structure which takes from years to decades to form. Healthy coral reefs differ from coral—rubble dominated reefs in microbial taxonomic composition and metabolic functional roles. The metabolisms of healthy reefs are dominated by autotrophic pathways, where carbon and nitrogen fixation dominate, while the metabolism of rubble—dominated reefs predominate in degradation of organic matter. Nitrogen fixation is 3 orders of magnitude lower in rubble—dominated reefs than in healthy reefs. Coral—rubble harbors a vast diversity of microbes that can precipitate carbonate through coupling several metabolic processes including photosynthesis, ureolysis, ammonification, denitrification, sulfate reduction, methane oxidation, and anaerobic sulfide oxidation. All these metabolic processes were found in rubble microbial communities, but ammonification and sulfate reduction were most prevalent. Anthropogenic and non—anthropogenic perturbations of healthy coral reefs in the past decades have led to the prevalence of rubble—dominated reefs in areas of the Caribbean where the ecological and functional shifts of the community still need further study.

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Infrared Scattering-Type Scanning Near-Field Optical Microscopy in Water

10.26434/chemrxiv.12279551.v1 ◽

2020 ◽

Author(s):

Emanuel Pfitzner ◽

Joachim Heberle

Keyword(s):

Optical Microscopy ◽

Laser Scanning ◽

Life Science ◽

Near Field ◽

Theoretical Models ◽

Bulk Solution ◽

Measured Quantity ◽

Ir Absorption ◽

Atomic Force ◽

Experimental Findings

<div><div><div><p>Infrared (IR) absorption spectroscopy detects state and chemical composition of biomolecules solely by their inherent vibrational fingerprints. Major disadvantages like the lack of spatial resolution and sensitivity were compensated lately by the use of pointed probes as local sensors enabling the detection of quantities as few as hundreds of proteins with nanometer precision. This makes infrared scattering-type scanning near-field optical microscopy a very powerful tool in life science. The strong absorption of infrared radiation of liquid water, however, still prevents to simply access the measured quantity – light scattered at the probing atomic force microscope tip. Here we report on the local IR response of biological membranes immersed in aqueous bulk solution. We make use of a silicon solid immersion lens as substrate and focusing optics to achieve detection efficiencies sufficient to yield IR near-field maps of purple membranes. We scrutinized our experimental findings by applying theoretical models. Finally, we suggest a means to improve the imaging quality by laser scanning assisted scattering-type scanning near-field optical microscopy. We believe that IR scattering-type scanning near-field optical microscopy will resolve biological structures in their native environments at nm resolution without the need for labeling.</p></div></div></div>

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Infrared Scattering-Type Scanning Near-Field Optical Microscopy in Water

10.26434/chemrxiv.12279551 ◽

2020 ◽

Author(s):

Emanuel Pfitzner ◽

Joachim Heberle

Keyword(s):

Optical Microscopy ◽

Laser Scanning ◽

Life Science ◽

Near Field ◽

Theoretical Models ◽

Bulk Solution ◽

Measured Quantity ◽

Ir Absorption ◽

Atomic Force ◽

Experimental Findings

<div><div><div><p>Infrared (IR) absorption spectroscopy detects state and chemical composition of biomolecules solely by their inherent vibrational fingerprints. Major disadvantages like the lack of spatial resolution and sensitivity were compensated lately by the use of pointed probes as local sensors enabling the detection of quantities as few as hundreds of proteins with nanometer precision. This makes infrared scattering-type scanning near-field optical microscopy a very powerful tool in life science. The strong absorption of infrared radiation of liquid water, however, still prevents to simply access the measured quantity – light scattered at the probing atomic force microscope tip. Here we report on the local IR response of biological membranes immersed in aqueous bulk solution. We make use of a silicon solid immersion lens as substrate and focusing optics to achieve detection efficiencies sufficient to yield IR near-field maps of purple membranes. We scrutinized our experimental findings by applying theoretical models. Finally, we suggest a means to improve the imaging quality by laser scanning assisted scattering-type scanning near-field optical microscopy. We believe that IR scattering-type scanning near-field optical microscopy will resolve biological structures in their native environments at nm resolution without the need for labeling.</p></div></div></div>

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Membrane-Assisted Crystallization: A Molecular View of NaCl Nucleation and Growth

Applied Sciences ◽

10.3390/app8112145 ◽

2018 ◽

Vol 8 (11) ◽

pp. 2145 ◽

Cited By ~ 3

Author(s):

Jheng-Han Tsai ◽

Maria Luisa Perrotta ◽

Annarosa Gugliuzza ◽

Francesca Macedonio ◽

Lidietta Giorno ◽

...

Keyword(s):

Sodium Chloride ◽

Polyvinylidene Fluoride ◽

Produced Water ◽

Theoretical Data ◽

Nucleation And Growth ◽

Crystal Nucleation ◽

Bulk Solution ◽

Face Centered Cubic ◽

Dynamics Simulations ◽

Experimental Findings

Membrane-assisted crystallization, aiming to induce supersaturation in a solution, has been successfully tested in the crystallization of ionic salts, low molecular organic acids, and proteins. Membrane crystallization is an emerging membrane process with the capability to simultaneously extract fresh water and valuable components from various streams. Successful application of crystallization for produced water treatment, seawater desalination, and salt recovery has been demonstrated. Recently, membrane crystallization has been developed to recover valuable minerals from highly concentrated solutions, since the recovery of high-quality minerals is expected to impact agriculture, pharmaceuticals, and household activities. In this work, molecular dynamics simulations were used to study the crystal nucleation and growth of sodium chloride in bulk and with hydrophobic polymer surfaces of polyvinylidene fluoride (PVDF) and polypropylene (PP) at a supersaturated concentration of salt. In parallel, membrane crystallization experiments were performed utilizing the same polymeric membranes in order to compare the experimental results with the computational ones. Moreover, the comparison in terms of nucleation time between the crystallization of sodium chloride (NaCl) using the traditional evaporation process and the membrane-assisted crystallization process was performed. Here, with an integrated experimental–computational approach, we demonstrate that the PVDF and PP membranes assist the crystal growth for NaCl, speeding up crystal nucleation in comparison to the bulk solution and leading to smaller and regularly structured face-centered cubic lattice NaCl crystals. This results in a mutual validation between theoretical data and experimental findings and provides the stimuli to investigate other mono and bivalent crystals with a new class of materials in advanced membrane separations.

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In situ identification of azo dye inhibition effects on nitrifying biofilms using microelectrodes

Water Science & Technology ◽

10.2166/wst.2002.0479 ◽

2002 ◽

Vol 46 (1-2) ◽

pp. 207-214 ◽

Cited By ~ 16

Author(s):

J. Li ◽

P.L. Bishop

Keyword(s):

Dissolved Oxygen ◽

Redox Potential ◽

Azo Dye ◽

Biofilm Reactor ◽

Bulk Solution ◽

Rotating Drum ◽

Acid Orange 7 ◽

Inhibitory Effects ◽

Nitrification Process

In this study, the inhibitory effects of acid orange 7 (AO7), a common azo dye, on nitrification in biofilms were investigated in situ using microelectrodes. Biofilms were obtained from laboratory rotating drum biofilm reactor after the nitrification process reached a pseudo-steady state. Dissolved oxygen, pH, NH4+, NO3−, and redox potential microelectrodes, with tip diameters ranging from 3–15 μm, were used to monitor the spatial distribution and change of microbial activities within nitrifying biofilms. It was found that at lower concentration (1 mg/L), AO7 had only a slight impact on the NH4+-N concentration profiles. The ammonium consumption rate decreased as higher AO7 concentrations (15 mg/L and 25 mg/L) were exposed to the biofilms. A similar trend was observed for the NO3−-N microprofiles. The nitrate production rate decreased as the AO7 concentration in the bulk solution increased. The dissolved oxygen and pH microprofiles also showed oxygen and alkalinity utilization, but at lower rates throughout the biofilms when the nitrification process was inhibited. No significant redox potential differences were observed in the biofilms after AO7 was applied.

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