scholarly journals Direct and Fe(II)-Mediated Reduction of Technetium by Fe(III)-Reducing Bacteria

2000 ◽  
Vol 66 (9) ◽  
pp. 3743-3749 ◽  
Author(s):  
J. R. Lloyd ◽  
V. A. Sole ◽  
C. V. G. Van Praagh ◽  
D. R. Lovley
Keyword(s):  
Dna Analysis ◽  
Limit Of Detection ◽  
Geobacter Sulfurreducens ◽  
Biogenic Magnetite ◽  
Enzymatic Reduction ◽  
Rapid Formation ◽  
Oxidation Of Hydrogen ◽  
Direct Cell ◽  
Reducing Bacteria ◽  
Mediated Reduction

ABSTRACT The dissimilatory Fe(III)-reducing bacterium Geobacter sulfurreducens reduced and precipitated Tc(VII) by two mechanisms. Washed cell suspensions coupled the oxidation of hydrogen to enzymatic reduction of Tc(VII) to Tc(IV), leading to the precipitation of TcO2 at the periphery of the cell. An indirect, Fe(II)-mediated mechanism was also identified. Acetate, although not utilized efficiently as an electron donor for direct cell-mediated reduction of technetium, supported the reduction of Fe(III), and the Fe(II) formed was able to transfer electrons abiotically to Tc(VII). Tc(VII) reduction was comparatively inefficient via this indirect mechanism when soluble Fe(III) citrate was supplied to the cultures but was enhanced in the presence of solid Fe(III) oxide. The rate of Tc(VII) reduction was optimal, however, when Fe(III) oxide reduction was stimulated by the addition of the humic analog and electron shuttle anthaquinone-2,6-disulfonate, leading to the rapid formation of the Fe(II)-bearing mineral magnetite. Under these conditions, Tc(VII) was reduced and precipitated abiotically on the nanocrystals of biogenic magnetite as TcO2 and was removed from solution to concentrations below the limit of detection by scintillation counting. Cultures of Fe(III)-reducing bacteria enriched from radionuclide-contaminated sediment using Fe(III) oxide as an electron acceptor in the presence of 25 μM Tc(VII) contained a singleGeobacter sp. detected by 16S ribosomal DNA analysis and were also able to reduce and precipitate the radionuclide via biogenic magnetite. Fe(III) reduction was stimulated in aquifer material, resulting in the formation of Fe(II)-containing minerals that were able to reduce and precipitate Tc(VII). These results suggest that Fe(III)-reducing bacteria may play an important role in immobilizing technetium in sediments via direct and indirect mechanisms.

scholarly journals Isolation and Characterization of Nitrate Reducing Bacteria for Conversion of Vegetable-Derived Nitrate to ‘Natural Nitrite’

2021 ◽  
Vol 1 (1) ◽  
pp. 11-23
Author(s):  
Arjun Bhusal ◽  
Peter M. Muriana
Keyword(s):  
Nitrate Reduction ◽  
High Performance ◽  
Limit Of Detection ◽  
Reversed Phase ◽  
Test Tube ◽  
Screening Assay ◽  
Isolation And Characterization ◽  
The Us ◽  
Reducing Bacteria ◽  
Nitrate Reducing Bacteria

In the US, sodium nitrate is used as a preservative and curing agent in processed meats and is therefore a regulated ingredient. Nitrate reducing bacteria (NRB) can convert vegetable nitrate into nitrite allowing green/clean label status in the US as per the USDA-FSIS definition of ‘natural nitrite’. The current ‘in-liquid’ test tube assay for detecting nitrite is not suitable for screening mixtures of bacteria nor is commercial nitrate broth suitable for growth of many Gram (+) bacteria. M17 broth was therefore used to develop M17-nitrate broth to be inclusive of Gram (+) bacteria. An ‘on-agar’ colony-screening assay was developed to detect the conversion of nitrate to nitrite on agar plates and could detect one NRB+ colony among ~300–500 colonies on a single plate. Samples that might have NRB were spread-plated on M17 agar plates, sandwiched with nitrate agar, and after incubation followed with sequential agar overlays containing the reagents used in the nitrate reduction assay; the appearance of red color zones above colonies indicated the presence of nitrite. NRB derived from various samples were confirmed for nitrate conversion and both nitrate and nitrite were quantified by C8 reversed-phase (RP) ion-pairing high performance liquid chromatography (HPLC) analysis (1 ppm limit of detection). Staphylococcus carnosus, a strain commonly used for nitrate reduction, was able to convert 1100 ppm M17-nitrate broth to 917 ppm nitrite. Staphylococcus caprae and Panteoa agglomerans, NRB isolated using the M17-nitrate agar assay, were also able to ferment the same broth to 916 ppm and 867 ppm nitrite, respectively. This is the first report of an on-agar colony screening assay for the detection and isolation of nitrite reducing bacteria allowing NRB to be readily isolated. This may allow for the identification of new bacteria that may have a more efficient process to generate nitrite, and possibly concomitant with production of additional natural antimicrobials, as vegetable nitrite becomes more widely used to prevent spore germination.

scholarly journals Biogenic Magnetite Formation through Anaerobic Biooxidation of Fe(II)

2001 ◽  
Vol 67 (6) ◽  
pp. 2844-2848 ◽  
Author(s):  
Swades K. Chaudhuri ◽  
Joseph G. Lack ◽  
John D. Coates
Keyword(s):  
Fine Grained ◽  
Biogenic Magnetite ◽  
Environmental Source ◽  
Reducing Bacteria ◽  
Magnetite Formation

ABSTRACT The presence of isotopically light carbonates in association with fine-grained magnetite is considered to be primarily due to the reduction of Fe(III) by Fe(III)-reducing bacteria in the environment. Here, we report on magnetite formation by biooxidation of Fe(II) coupled to denitrification. This metabolism offers an alternative environmental source of biogenic magnetite.

scholarly journals Growth of Geobacter sulfurreducens with Acetate in Syntrophic Cooperation with Hydrogen-Oxidizing Anaerobic Partners

1998 ◽  
Vol 64 (6) ◽  
pp. 2232-2236 ◽  
Author(s):  
Ralf Cord-Ruwisch ◽  
Derek R. Lovley ◽  
Bernhard Schink
Keyword(s):  
Electron Transfer ◽  
Electron Acceptor ◽  
Hydrogen Transfer ◽  
Dry Mass ◽  
Geobacter Sulfurreducens ◽  
Acetate Oxidation ◽  
Yield Data ◽  
Partial Pressures ◽  
Production Of Hydrogen ◽  
Reducing Bacteria

ABSTRACT Pure cultures of Geobacter sulfurreducens and other Fe(III)-reducing bacteria accumulated hydrogen to partial pressures of 5 to 70 Pa with acetate, butyrate, benzoate, ethanol, lactate, or glucose as the electron donor if electron release to an acceptor was limiting. G. sulfurreducens coupled acetate oxidation with electron transfer to an anaerobic partner bacterium in the absence of ferric iron or other electron acceptors. Cocultures of G. sulfurreducens and Wolinella succinogenes with nitrate as the electron acceptor degraded acetate efficiently and grew with doubling times of 6 to 8 h. The hydrogen partial pressures in these acetate-degrading cocultures were considerably lower, in the range of 0.02 to 0.04 Pa. From these values and the concentrations of the other reactants, it was calculated that in this cooperation the free energy change available to G. sulfurreducens should be about −53 kJ per mol of acetate oxidized, assuming complete conversion of acetate to CO2 and H2. However, growth yields (18.5 g of dry mass per mol of acetate for the coculture, about 14 g for G. sulfurreducens) indicated considerably higher energy gains. These yield data, measurement of hydrogen production rates, and calculation of the diffusive hydrogen flux indicated that electron transfer in these cocultures may not proceed exclusively via interspecies hydrogen transfer but may also proceed through an alternative carrier system with higher redox potential, e.g., a c-type cytochrome that was found to be excreted byG. sulfurreducens into the culture fluid. Syntrophic acetate degradation was also possible with G. sulfurreducens and Desulfovibrio desulfuricans CSN but only with nitrate as electron acceptor. These cultures produced cell yields of 4.5 g of dry mass per mol of acetate, to which both partners contributed at about equal rates. These results demonstrate that some Fe(III)-reducing bacteria can oxidize organic compounds under Fe(III) limitation with the production of hydrogen, and they provide the first example of rapid acetate oxidation via interspecies electron transfer at moderate temperature.

scholarly journals Isolation and Characterization of Chromate Resistant and Reducing Bacteria from Tannery Effluent of Chittagong, Bangladesh

1970 ◽  
Vol 17 ◽  
pp. 71-76
Author(s):  
M Fakruddin ◽  
Reaz Mohammad Mazumder ◽  
Towhida Khanom Tania ◽  
Saiful Islam ◽  
Meher Nigad Nipa ◽  
...  
Keyword(s):  
Atomic Absorption Spectrophotometry ◽  
Luria Bertani ◽  
Tannery Effluent ◽  
Bacterial Strains ◽  
E Coli ◽  
Absorption Spectrophotometry ◽  
Isolation And Characterization ◽  
Enzymatic Reduction ◽  
Reducing Bacteria

Context: Waste water containing Chromium (Cr6+) is by far the most important environmental challenge being faced. Objectives: The present study was planned on the isolation and characterization of chromate resistant and reducing bacterial strains in order to use them for detoxification of chromate.Materials and Methods: Water samples were collected to isolate microorganisms from tannery effluent of Baluchara, Chittagong and inoculated into Luria-Bertani medium with added Cr6+ as K2Cr2O7. The organisms have been identified and studied for Cr6+ reduction-ability in growth dependent manner.Results: A total of 35 isolates have been selected as potential organism belonging to the species of Moraxella (14.3%), Bacillus (11.43%), Streptococcus (25.72%), Staphylococcus (5.7%), Salmonella (12.3%), E. coli (13.3%), Enterobacter (11.3%), Hafnia alvei (2.45%) and Alcaligenes (3.5%). The selected isolates were able to tolerate at least 500 mg/l of Cr6+. The total Cr6+ concentration of the effluent sample analysed was found to be about 23.73 mg/l as determined by Atomic Absorption Spectrophotometry. Two of the isolates reduced 38% and 32% of Cr6+ added to the medium. Another 7 isolates showed Cr6+; reducing capability ranging from 18 to 22%.Conclusion: As the isolates have turned out to successfully reduce Cr6+ in this study, these can be used for the development of bioremediation process. Key words: Enzymatic reduction; Bioremediation; Chromium; Ecotoxicity; Tannery.DOI: 10.3329/jbs.v17i0.7104J. bio-sci. 17: 71-76, 2009

scholarly journals Succinate dehydrogenase functioning by a reverse redox loop mechanism and fumarate reductase in sulphate-reducing bacteria

Microbiology ◽  
2006 ◽  
Vol 152 (8) ◽  
pp. 2443-2453 ◽  
Author(s):  
Tanja Zaunmüller ◽  
David J. Kelly ◽  
Frank O. Glöckner ◽  
Gottfried Unden
Keyword(s):  
Succinate Dehydrogenase ◽  
Draft Genome ◽  
Desulfovibrio Desulfuricans ◽  
Geobacter Sulfurreducens ◽  
Fumarate Reductase ◽  
Desulfovibrio Vulgaris ◽  
Succinate Oxidation ◽  
Proton Potential ◽  
Fumarate Respiration ◽  
Reducing Bacteria

Sulphate- or sulphur-reducing bacteria with known or draft genome sequences (Desulfovibrio vulgaris, Desulfovibrio desulfuricans G20, Desulfobacterium autotrophicum [draft], Desulfotalea psychrophila and Geobacter sulfurreducens) all contain sdhCAB or frdCAB gene clusters encoding succinate : quinone oxidoreductases. frdD or sdhD genes are missing. The presence and function of succinate dehydrogenase versus fumarate reductase was studied. Desulfovibrio desulfuricans (strain Essex 6) grew by fumarate respiration or by fumarate disproportionation, and contained fumarate reductase activity. Desulfovibrio vulgaris lacked fumarate respiration and contained succinate dehydrogenase activity. Succinate oxidation by the menaquinone analogue 2,3-dimethyl-1,4-naphthoquinone depended on a proton potential, and the activity was lost after degradation of the proton potential. The membrane anchor SdhC contains four conserved His residues which are known as the ligands for two haem B residues. The properties are very similar to succinate dehydrogenase of the Gram-positive (menaquinone-containing) Bacillus subtilis, which uses a reverse redox loop mechanism in succinate : menaquinone reduction. It is concluded that succinate dehydrogenases from menaquinone-containing bacteria generally require a proton potential to drive the endergonic succinate oxidation. Sequence comparison shows that the SdhC subunit of this type lacks a Glu residue in transmembrane helix IV, which is part of the uncoupling E-pathway in most non-electrogenic FrdABC enzymes.

scholarly journals Geobacter sulfurreducens inner membrane cytochrome CbcBA controls electron transfer and growth yield near the energetic limit of respiration

2021 ◽  
Author(s):  
Komal Joshi ◽  
Chi Ho Chan ◽  
Daniel R. Bond
Keyword(s):  
Electron Transfer ◽  
Redox Potential ◽  
Growth Yield ◽  
Growth Efficiency ◽  
Geobacter Sulfurreducens ◽  
Redox Potentials ◽  
Hydrogen Electrode ◽  
Highly Expressed Genes ◽  
Reducing Bacteria ◽  
Transfer Chain

AbstractGeobacter sulfurreducens utilizes extracellular electron acceptors such as Mn(IV), Fe(III), syntrophic partners, and electrodes that vary from +0.4 to −0.3 V vs. Standard Hydrogen Electrode (SHE), representing a potential energy span that should require a highly branched electron transfer chain. Here we describe CbcBA, a bc-type cytochrome essential near the thermodynamic limit of respiration when acetate is the electron donor. Mutants lacking cbcBA ceased Fe(III) reduction at −0.21 V vs. SHE, could not transfer electrons to electrodes between −0.21 and −0.28 V, and could not reduce the final 10% – 35% of Fe(III) minerals. As redox potential decreased during Fe(III) reduction, cbcBA was induced with the aid of the regulator BccR to become one of the most highly expressed genes in G. sulfurreducens. Growth yield (CFU/mM Fe(II)) was 112% of WT in ΔcbcBA, and deletion of cbcL (a different bc-cytochrome essential near −0.15 V) in ΔcbcBA increased yield to 220%. Together with ImcH, which is required at high redox potentials, CbcBA represents a third cytoplasmic membrane oxidoreductase in G. sulfurreducens. This expanding list shows how these important metal-reducing bacteria may constantly sense redox potential to adjust growth efficiency in changing environments.

scholarly journals Interactions between the Fe(III)-Reducing Bacterium Geobacter sulfurreducens and Arsenate, and Capture of the Metalloid by Biogenic Fe(II)

2005 ◽  
Vol 71 (12) ◽  
pp. 8642-8648 ◽  
Author(s):  
F. S. Islam ◽  
R. L. Pederick ◽  
A. G. Gault ◽  
L. K. Adams ◽  
D. A. Polya ◽  
...  
Keyword(s):  
Microbial Communities ◽  
Electron Acceptor ◽  
West Bengal ◽  
Arsenic Species ◽  
Geobacter Sulfurreducens ◽  
Terminal Electron Acceptor ◽  
Genetic Potential ◽  
Enzymatic Reduction ◽  
Culture Supernatants ◽  
Ferrous Carbonate

ABSTRACT Previous work has shown that microbial communities in As-mobilizing sediments from West Bengal were dominated by Geobacter species. Thus, the potential of Geobacter sulfurreducens to mobilize arsenic via direct enzymatic reduction and indirect mechanisms linked to Fe(III) reduction was analyzed. G. sulfurreducens was unable to conserve energy for growth via the dissimilatory reduction of As(V), although it was able to grow in medium containing fumarate as the terminal electron acceptor in the presence of 500 μM As(V). There was also no evidence of As(III) in culture supernatants, suggesting that resistance to 500 μM As(V) was not mediated by a classical arsenic resistance operon, which would rely on the intracellular reduction of As(V) and the efflux of As(III). When the cells were grown using soluble Fe(III) as an electron acceptor in the presence of As(V), the Fe(II)-bearing mineral vivianite was formed. This was accompanied by the removal of As, predominantly as As(V), from solution. Biogenic siderite (ferrous carbonate) was also able to remove As from solution. When the organism was grown using insoluble ferrihydrite as an electron acceptor, Fe(III) reduction resulted in the formation of magnetite, again accompanied by the nearly quantitative sorption of As(V). These results demonstrate that G. sulfurreducens, a model Fe(III)-reducing bacterium, did not reduce As(V) enzymatically, despite the apparent genetic potential to mediate this transformation. However, the reduction of Fe(III) led to the formation of Fe(II)-bearing phases that are able to capture arsenic species and could act as sinks for arsenic in sediments.

scholarly journals DIPG-08. ELECTRONIC SEQUENCING PROVIDES OPTIMIZED QUANTIFICATION OF SERIAL, MULTI-GENE MOLECULAR RESPONSE IN THE CSF OF CHILDREN WITH HIGH-GRADE GLIOMA

2020 ◽  
Vol 22 (Supplement_3) ◽  
pp. iii288-iii288
Author(s):  
Amy Bruzek ◽  
Ashwath Muruganand ◽  
Karthik Ravi ◽  
Jack Wadden ◽  
Clarissa Babila ◽  
...  
Keyword(s):  
Dna Analysis ◽  
Limit Of Detection ◽  
High Grade Glioma ◽  
Patient Specific ◽  
Molecular Response ◽  
High Grade ◽  
Non Invasive ◽  
Oxford Nanopore ◽  
Recurrent Mutations ◽  
Analysis Platform

Abstract BACKGROUND For pediatric high-grade glioma (pHGG), non-invasive methods for diagnosis and surveillance are needed. Tumors release DNA (tDNA) into cerebrospinal fluid (CSF), allowing for detection of tumor-associated mutations by CSF sampling. We hypothesized that direct, electronic analysis of tDNA with a novel, hand-held platform (Oxford Nanopore MinION) could quantify patient-specific CSF tDNA variant allele fraction (VAF) with improved speed and limit of detection compared to established methods. METHODS We integrated required multi-timepoint (0, 2, and 6 months) correlate lumbar punctures (LP) in two ongoing pHGG clinical trials. Using Nanopore technology, we performed amplicon-based PCR on CSF tDNA for recurrent mutations from patient samples (n=19) and normal controls. VAF were determined via MinKNOW, Guppy, MiniMap2, and Integrated Genome Browser. RESULTS Nanopore CSF tDNA demonstrated improved sensitivity (91%) when compare to NGS sequencing (50%). Nanopore analysis of serially diluted CSF sample demonstrated significantly lower limit of detection (attomolar) than typical NGS sample requirement (nanomolar). H3K27M mutation was reliably detected with 1,000x depth sequencing, which was achieved in less than 15 minutes of sequencing after amplification. Multiplexed Nanopore analysis of H3F3A and HIST1H3B was employed when H3 status was unknown. Serial CSF tDNA analysis confirmed multi-gene (H3F3A K27M, PIK3CA, and TP53) molecular remission in a 17-year-old with thalamic diffuse midline glioma that correlated with sustained clinical response to ONC201 (14 months and ongoing). CONCLUSIONS Use of a hand-held, electronic DNA analysis platform allows quantification of multi-gene molecular response with improved speed and limit of detection in the CSF of children with high-grade glioma.

Potential role of the Fe(III)-reducing bacteriaGeobacterandGeothrixin controlling arsenic solubility in Bengal delta sediments

2005 ◽  
Vol 69 (5) ◽  
pp. 865-875 ◽  
Author(s):  
F. S. Islam ◽  
C. Boothman ◽  
A. G. Gault ◽  
D. A. Polya ◽  
J. R. Lloyd
Keyword(s):  
Electron Acceptor ◽  
Enrichment Culture ◽  
Anaerobic Bacteria ◽  
Defined Medium ◽  
Geobacter Sulfurreducens ◽  
Close Relative ◽  
Bengal Delta ◽  
Delta Sediments ◽  
Reducing Bacteria ◽  
Geothrix Fermentans

AbstractPrevious studies from our laboratory have suggested a role for indigenous metal-reducing bacteria in the reduction of sediment-bound As(V), and have also shown that a stable enrichment culture of Fe(III)-reducing bacteria was able to mobilize arsenic (as As(III)) from sediments collected from West Bengal (Islamet al., 2004). To identify the Fe(III)-reducing bacteria that may play a role in the reduction of As(V) and mobilization of As(III), we made a detailed molecular analysis of this enrichment culture. It was dominated by a close relative ofGeothrix fermentans, but the type strain of this organism was unable to conserve energy for growth via the dissimilatory reduction of As(V), or reduce As(V) present in a defined medium containing fumarate as the electron acceptor. Furthermore, when the cells were grown using soluble Fe(III)-citrate as an electron acceptor in the presence of As(V), bacterial Fe(III) reduction resulted in the precipitation of the Fe(II)-bearing mineral vivianite in 2 weeks. This was accompanied by the efficient removal of As from solution. These results demonstrate thatGeothrix fermentans, in common with other key Fe(III)-reducing bacteria such asGeobacter sulfurreducens, does not reduce As(V) enzymatically, but can capture arsenic in Fe(II) minerals formed during respiration using Fe(III) as an electron acceptor. Thus, the reduction of arsenic-bearing Fe(III) oxide minerals is not sufficient to mobilize arsenic, but may result in the formation of Fe(II) biominerals that could potentially act as sinks for arsenic in sediments. Additional mechanisms, including dissimilatory As(V) reduction by other specialist anaerobic bacteria, are implicated in the mobilization of arsenic from sediments.

scholarly journals An Inner Membrane Cytochrome Required Only for Reduction of High Redox Potential Extracellular Electron Acceptors

mBio ◽  
2014 ◽  
Vol 5 (6) ◽  
Author(s):  
Caleb E. Levar ◽  
Chi Ho Chan ◽  
Misha G. Mehta-Kolte ◽  
Daniel R. Bond
Keyword(s):  
Electron Transfer ◽  
Electron Acceptors ◽  
Geobacter Sulfurreducens ◽  
Extracellular Electron Transfer ◽  
Redox Potentials ◽  
Inner Membrane ◽  
Content Type ◽  
Transfer Strategies ◽  
Reducing Bacteria ◽  
Metal Reducing Bacteria

ABSTRACTDissimilatory metal-reducing bacteria, such asGeobacter sulfurreducens, transfer electrons beyond their outer membranes to Fe(III) and Mn(IV) oxides, heavy metals, and electrodes in electrochemical devices. In the environment, metal acceptors exist in multiple chelated and insoluble forms that span a range of redox potentials and offer different amounts of available energy. Despite this, metal-reducing bacteria have not been shown to alter their electron transfer strategies to take advantage of these energy differences. Disruption ofimcH, encoding an inner membranec-type cytochrome, eliminated the ability ofG. sulfurreducensto reduce Fe(III) citrate, Fe(III)-EDTA, and insoluble Mn(IV) oxides, electron acceptors with potentials greater than 0.1 V versus the standard hydrogen electrode (SHE), but theimcHmutant retained the ability to reduce Fe(III) oxides with potentials of ≤−0.1 V versus SHE. TheimcHmutant failed to grow on electrodes poised at +0.24 V versus SHE, but switching electrodes to −0.1 V versus SHE triggered exponential growth. At potentials of ≤−0.1 V versus SHE, both the wild type and theimcHmutant doubled 60% slower than at higher potentials. Electrodes poised even 100 mV higher (0.0 V versus SHE) could not triggerimcHmutant growth. These results demonstrate thatG. sulfurreducenspossesses multiple respiratory pathways, that some of these pathways are in operation only after exposure to low redox potentials, and that electron flow can be coupled to generation of different amounts of energy for growth. The redox potentials that trigger these behaviors mirror those of metal acceptors common in subsurface environments whereGeobacteris found.IMPORTANCEInsoluble metal oxides in the environment represent a common and vast reservoir of energy for respiratory microbes capable of transferring electrons across their insulating membranes to external acceptors, a process termed extracellular electron transfer. Despite the global biogeochemical importance of metal cycling and the ability of such organisms to produce electricity at electrodes, fundamental gaps in the understanding of extracellular electron transfer biochemistry exist. Here, we describe a conserved inner membrane redox protein inGeobacter sulfurreducenswhich is required only for electron transfer to high-potential compounds, and we show thatG. sulfurreducenshas the ability to utilize different electron transfer pathways in response to the amount of energy available in a metal or electrode distant from the cell.

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