Effects of medium composition on cell pigmentation, cytochrome content, and ferric iron reduction in a Pseudomonas sp. isolated from crude oil

1982 ◽  
Vol 28 (8) ◽  
pp. 989-992 ◽  
Author(s):  
C. O. Obuekwe ◽  
D. W. S. Westlake
Keyword(s):  
Iron Reduction ◽  
Direct Relationship ◽  
Ferric Iron ◽  
Synthetic Medium ◽  
Medium Composition ◽  
Terminal Electron Acceptor ◽  
Spectrophotometric Data ◽  
Cytochrome Content ◽  
Orange Color ◽  
Pipeline Corrosion

Cells of a pseudomonad associated with pipeline corrosion grown on a complex medium were orange in color and vigorously reduced ferric iron. The intensity of orange color of cells grown on a synthetic medium and their ability to reduce ferric iron was directly related to the iron content of the medium. Absorption spectrophotometric data show a direct relationship between color of cells, cytochrome content, and ability to reduce ferric iron. Carbon monoxide markedly, but not completely, inhibits the reduction of ferric iron. The data presented indicate that ferric iron can serve as a terminal electron acceptor for cytochrome-associated respiratory processes of this corrosive pseudomonad.

Reduction of Soluble and Solid Ferric Iron by Acidiphilium SJH

2007 ◽  
Vol 20-21 ◽  
pp. 497-500 ◽  
Author(s):  
Alexandra Vašková ◽  
Daniel Kupka
Keyword(s):  
Iron Reduction ◽  
Consumption Rate ◽  
Ferric Iron ◽  
Oxygen Transfer Rate ◽  
Oxygen Limitation ◽  
Co2 Production ◽  
Anaerobic Conditions ◽  
Terminal Electron Acceptor ◽  
Aerobic Conditions ◽  
Microaerobic Conditions

Facultative Fe(III)-reducing bacterium Acidiphilium SJH was incubated in media with ferric iron under various conditions with respect to oxygen availability for the growing cells. The bacteria oxidized organic substratum to carbon dioxide using oxygen and ferric iron as terminal electron acceptors. Ferric iron reduction was observed in all incubation modes. The distribution of reducing equivalents from the oxidation of organic carbon for the reduction of both O2 and Fe(III) was evaluated from CO2 production rate and O2 consumption rate. In fully aerobic conditions approximately 10 % of CO2 produced was coupled with reduction of Fe(III) as terminal electron acceptor. Under aerobic conditions, the ratio of CO2 produced to O2 consumed remained unaffected in a broad concentration range of dissolved oxygen. In the course of oxygen limitation (microaerobic conditions) the molar CO2 to O2 ratio increased from approx. 1 to 2 and even much more with respect to oxygen transfer rate during incubation. On the other hand no bacterial growth and extremely slow iron reduction was observed in obligatory anaerobic conditions in a reactor purged with either pure or CO2-enriched nitrogen.

scholarly journals Ferric Iron Reduction by Bacteria Associated with the Roots of Freshwater and Marine Macrophytes

1999 ◽  
Vol 65 (10) ◽  
pp. 4393-4398 ◽  
Author(s):  
G. M. King ◽  
Meredith A. Garey
Keyword(s):  
Iron Reduction ◽  
Ferric Iron ◽  
Sodium Molybdate ◽  
Dry Weight ◽  
Root Activity ◽  
In Vitro Assays ◽  
Freshwater Macrophytes ◽  
Marine Macrophytes ◽  
Marine Isolate

ABSTRACT In vitro assays of washed, excised roots revealed maximum potential ferric iron reduction rates of >100 μmol g (dry weight)−1 day−1 for three freshwater macrophytes and rates between 15 and 83 μmol (dry weight)−1 day−1 for two marine species. The rates varied with root morphology but not consistently (fine root activity exceeded smooth root activity in some but not all cases). Sodium molybdate added at final concentrations of 0.2 to 20 mM did not inhibit iron reduction by roots of marine macrophytes (Spartina alterniflora and Zostera marina). Roots of a freshwater macrophyte, Sparganium eurycarpum, that were incubated with an analog of humic acid precursors, anthroquinone disulfate (AQDS), reduced freshly precipitated iron oxyhydroxide contained in dialysis bags that excluded solutes with molecular weights of >1,000; no reduction occurred in the absence of AQDS. Bacterial enrichment cultures and isolates from freshwater and marine roots used a variety of carbon and energy sources (e.g., acetate, ethanol, succinate, toluene, and yeast extract) and ferric oxyhydroxide, ferric citrate, uranate, and AQDS as terminal electron acceptors. The temperature optima for a freshwater isolate and a marine isolate were equivalent (approximately 32°C). However, iron reduction by the freshwater isolate decreased with increasing salinity, while reduction by the marine isolate displayed a relatively broad optimum salinity between 20 and 35 ppt. Our results suggest that by participating in an active iron cycle and perhaps by reducing humic acids, iron reducers in the rhizoplane of aquatic macrophytes limit organic availability to other heterotrophs (including methanogens) in the rhizosphere and bulk sediments.

scholarly journals Vibrio cholerae VciB Mediates Iron Reduction

2017 ◽  
Vol 199 (12) ◽  
Author(s):  
Eric D. Peng ◽  
Shelley M. Payne
Keyword(s):  
Electron Transport ◽  
Vibrio Cholerae ◽  
Ferrous Iron ◽  
Electron Transport Chain ◽  
Iron Reduction ◽  
Iron Transport ◽  
Ferric Iron ◽  
Transport Systems ◽  
Content Type ◽  
Transport Chain

ABSTRACT Vibrio cholerae is the causative agent of the severe diarrheal disease cholera. V. cholerae thrives within the human host, where it replicates to high numbers, but it also persists within the aquatic environments of ocean and brackish water. To survive within these nutritionally diverse environments, V. cholerae must encode the necessary tools to acquire the essential nutrient iron in all forms it may encounter. A prior study of systems involved in iron transport in V. cholerae revealed the existence of vciB, which, while unable to directly transport iron, stimulates the transport of iron through ferrous (Fe2+) iron transport systems. We demonstrate here a role for VciB in V. cholerae in which VciB stimulates the reduction of Fe3+ to Fe2+, which can be subsequently transported into the cell with the ferrous iron transporter Feo. Iron reduction is independent of functional iron transport but is associated with the electron transport chain. Comparative analysis of VciB orthologs suggests a similar role for other proteins in the VciB family. Our data indicate that VciB is a dimer located in the inner membrane with three transmembrane segments and a large periplasmic loop. Directed mutagenesis of the protein reveals two highly conserved histidine residues required for function. Taken together, our results support a model whereby VciB reduces ferric iron using energy from the electron transport chain. IMPORTANCE Vibrio cholerae is a prolific human pathogen and environmental organism. The acquisition of essential nutrients such as iron is critical for replication, and V. cholerae encodes a number of mechanisms to use iron from diverse environments. Here, we describe the V. cholerae protein VciB that increases the reduction of oxidized ferric iron (Fe3+) to the ferrous form (Fe2+), thus promoting iron acquisition through ferrous iron transporters. Analysis of VciB orthologs in Burkholderia and Aeromonas spp. suggest that they have a similar activity, allowing a functional assignment for this previously uncharacterized protein family. This study builds upon our understanding of proteins known to mediate iron reduction in bacteria.

Reduction and Complexation of Copper in a Novel Bioreduction System Developed to Recover Base Metals from Mine Process Waters

2013 ◽  
Vol 825 ◽  
pp. 483-486 ◽  
Author(s):  
Sabrina Hedrich ◽  
Chris du Plessis ◽  
Nelson Mora ◽  
D. Barrie Johnson
Keyword(s):  
Copper Sulfide ◽  
Iron Reduction ◽  
Elemental Sulfur ◽  
Ferric Iron ◽  
Sodium Sulfide ◽  
Base Metals ◽  
Processing Scheme ◽  
Step Process ◽  
Potential Alternative ◽  
Axenic Cultures

An integrated bio-processing scheme was devised and tested in the laboratory for recovering copper, or other base metals, from pregnant leach solutions (PLS) using a two-step process involving both iron-reduction, and sulfate-reduction for H2S generation and sulfide precipitation, as a potential alternative to conventional SX-EW. Reduction of ferric iron in the PLS was achieved using iron-reducingAcidithiobacillusspp. andSulfobacillus thermosulfidooxidansin column reactors containing elemental sulfur as electron donor. Analysis of the column reactor effluents showed not only that most of the ferric iron was reduced to ferrous, but also that all of the copper (II) had been reduced to copper (I), i.e. cuprous copper. This copper (I) appeared to be complexed as it was not oxidized when exposed to ferric iron nor precipitated as a copper-sulfide when exposed to either sodium sulfide or H2S. The data suggested that copper (II) was reduced and the resulting copper (I) complexed, with both reactions probably mediated by sulfur oxy-anions produced indirectly by the bacteria, in the anoxic sulfur column bioreactors. It was also noted that copper (I) produced chemically by reduction of copper (II) by hydroxylamine was more toxic to axenic cultures ofAcidithiobacillusspp. andSb. thermosulfidooxidansthan was the copper (I) in the column effluent liquors.

Influence of dietary phenolic acids on redox status of iron: Ferrous iron autoxidation and ferric iron reduction

2008 ◽  
Vol 106 (2) ◽  
pp. 650-660 ◽  
Author(s):  
Kateřina Chvátalová ◽  
Iva Slaninová ◽  
Lenka Březinová ◽  
Jiří Slanina
Keyword(s):  
Phenolic Acids ◽  
Ferrous Iron ◽  
Iron Reduction ◽  
Ferric Iron ◽  
Redox Status

scholarly journals A new transgenic rice line exhibiting enhanced ferric iron reduction and phytosiderophore production confers tolerance to low iron availability in calcareous soil

PLoS ONE ◽  
2017 ◽  
Vol 12 (3) ◽  
pp. e0173441 ◽  
Author(s):  
Hiroshi Masuda ◽  
Erika Shimochi ◽  
Tatsuro Hamada ◽  
Takeshi Senoura ◽  
Takanori Kobayashi ◽  
...  
Keyword(s):  
Transgenic Rice ◽  
Calcareous Soil ◽  
Iron Reduction ◽  
Ferric Iron ◽  
Iron Availability ◽  
Rice Line ◽  
Transgenic Rice Line

scholarly journals Ferric Iron Reduction in Extreme Acidophiles

2022 ◽  
Vol 12 ◽  
Author(s):  
Luise Malik ◽  
Sabrina Hedrich
Keyword(s):  
Iron Reduction ◽  
Ferric Iron ◽  
Hydrogen Oxidation ◽  
Iron Oxidation ◽  
Minor Role ◽  
Microbial Conversion ◽  
Dissimilatory Iron Reduction ◽  
Alternative Scenarios ◽  
A Minor ◽  
Life On Earth

Biochemical processes are a key element of natural cycles occurring in the environment and enabling life on earth. With regard to microbially catalyzed iron transformation, research predominantly has focused on iron oxidation in acidophiles, whereas iron reduction played a minor role. Microbial conversion of ferric to ferrous iron has however become more relevant in recent years. While there are several reviews on neutrophilic iron reducers, this article summarizes the research on extreme acidophilic iron reducers. After the first reports of dissimilatory iron reduction by acidophilic, chemolithoautotrophic Acidithiobacillus strains and heterotrophic Acidiphilium species, many other prokaryotes were shown to reduce iron as part of their metabolism. Still, little is known about the exact mechanisms of iron reduction in extreme acidophiles. Initially, hypotheses and postulations for the occurring mechanisms relied on observations of growth behavior or predictions based on the genome. By comparing genomes of well-studied neutrophilic with acidophilic iron reducers (e.g., Ferroglobus placidus and Sulfolobus spp.), it became clear that the electron transport for iron reduction proceeds differently in acidophiles. Moreover, transcriptomic investigations indicated an enzymatically-mediated process in Acidithiobacillus ferrooxidans using respiratory chain components of the iron oxidation in reverse. Depending on the strain of At. ferrooxidans, further mechanisms were postulated, e.g., indirect iron reduction by hydrogen sulfide, which may form by disproportionation of elemental sulfur. Alternative scenarios include Hip, a high potential iron-sulfur protein, and further cytochromes. Apart from the anaerobic iron reduction mechanisms, sulfur-oxidizing acidithiobacilli have been shown to mediate iron reduction at low pH (< 1.3) under aerobic conditions. This presumably non-enzymatic process may be attributed to intermediates formed during sulfur/tetrathionate and/or hydrogen oxidation and has already been successfully applied for the reductive bioleaching of laterites. The aim of this review is to provide an up-to-date overview on ferric iron reduction by acidophiles. The importance of this process in anaerobic habitats will be demonstrated as well as its potential for application.

scholarly journals Helicobacter pylori ribBA-Mediated Riboflavin Production Is Involved in Iron Acquisition

1998 ◽  
Vol 180 (6) ◽  
pp. 1473-1479 ◽  
Author(s):  
Dennis J. Worst ◽  
Monique M. Gerrits ◽  
Christina M. J. E. Vandenbroucke-Grauls ◽  
Johannes G. Kusters
Keyword(s):  
Helicobacter Pylori ◽  
Iron Reduction ◽  
Ferric Iron ◽  
Iron Acquisition ◽  
Cosmid Library ◽  
Dot Blot ◽  
E Coli ◽  
Reduction Activity ◽  
Dna Fragment ◽  
H Pylori

ABSTRACT In this study, we cloned and sequenced a DNA fragment from an ordered cosmid library of Helicobacter pylori NCTC 11638 which confers to a siderophore synthesis mutant of Escherichia coli (EB53 aroB hemA) the ability to grow on iron-restrictive media and to reduce ferric iron. Sequence analysis of the DNA fragment revealed the presence of an open reading frame with high homology to the ribA gene of Bacillus subtilis. This gene encodes a bifunctional enzyme with the activities of both 3,4-dihydroxy-2-butanone 4-phosphate (DHBP) synthase and GTP cyclohydrolase II, which catalyze two essential steps in riboflavin biosynthesis. Expression of the gene (designatedribBA) resulted in the formation of one translational product, which was able to complement both the ribA and theribB mutation in E. coli. Expression ofribBA was iron regulated, as was suggested by the presence of a putative FUR box in its promotor region and as shown by RNA dot blot analysis. Furthermore, we showed that production of riboflavin inH. pylori cells is iron regulated. E. coliEB53 containing the plasmid with H. pylori ribBAexcreted riboflavin in the culture medium, and this riboflavin excretion also appeared to be iron regulated. We postulate that the iron-regulated production of riboflavin and ferric-iron-reduction activity by E. coli EB53 transformed with the H. pylori ribBA gene is responsible for the survival of EB53 on iron-restrictive medium. Because disruption of ribBA inH. pylori eliminates its ferric-iron-reduction activity, we conclude that ribBA has an important role in ferric-iron reduction and iron acquisition by H. pylori.

scholarly journals Ferrihydrite-Dependent Growth of Sulfurospirillum deleyianum through Electron Transfer via Sulfur Cycling

2004 ◽  
Vol 70 (10) ◽  
pp. 5744-5749 ◽  
Author(s):  
Kristina L. Straub ◽  
Bernhard Schink
Keyword(s):  
Electron Acceptor ◽  
Ferrous Iron ◽  
Iron Reduction ◽  
Ferric Iron ◽  
Sulfide Oxidation ◽  
Microbial Reduction ◽  
Sulfur Cycle ◽  
Sulfur Cycling ◽  
Sulfur Source ◽  
Sulfur Species

ABSTRACT Observations in enrichment cultures of ferric iron-reducing bacteria indicated that ferrihydrite was reduced to ferrous iron minerals via sulfur cycling with sulfide as the reductant. Ferric iron reduction via sulfur cycling was investigated in more detail with Sulfurospirillum deleyianum, which can utilize sulfur or thiosulfate as an electron acceptor. In the presence of cysteine (0.5 or 2 mM) as the sole sulfur source, no (microbial) reduction of ferrihydrite or ferric citrate was observed, indicating that S. deleyianum is unable to use ferric iron as an immediate electron acceptor. However, with thiosulfate at a low concentration (0.05 mM), growth with ferrihydrite (6 mM) was possible and sulfur was cycled up to 60 times. Also, spatially distant ferrihydrite in agar cultures was reduced via diffusible sulfur species. Due to the low concentrations of thiosulfate, S. deleyianum produced only small amounts of sulfide. Obviously, sulfide delivered electrons to ferrihydrite with no or only little precipitation of black iron sulfides. Ferrous iron and oxidized sulfur species were produced instead, and the latter served again as the electron acceptor. These oxidized sulfur species have not yet been identified. However, sulfate and sulfite cannot be major products of ferrihydrite-dependent sulfide oxidation, since neither compound can serve as an electron acceptor for S. deleyianum. Instead, sulfur (elemental S or polysulfides) and/or thiosulfate as oxidized products could complete a sulfur cycle-mediated reduction of ferrihydrite.

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