scholarly journals Constraints on Anaerobic Respiration in the Hyperthermophilic Archaea Pyrobaculum islandicum and Pyrobaculum aerophilum

2007 ◽  
Vol 74 (2) ◽  
pp. 396-402 ◽  
Author(s):  
Lawrence F. Feinberg ◽  
R. Srikanth ◽  
Richard W. Vachet ◽  
James F. Holden
Keyword(s):  
Iron Oxide ◽  
Growth Rates ◽  
Direct Contact ◽  
Iron Reduction ◽  
Elemental Sulfur ◽  
Reductase Activity ◽  
Anaerobic Respiration ◽  
Hyperthermophilic Archaea ◽  
Pyrobaculum Aerophilum ◽  
Pyrobaculum Islandicum

ABSTRACT Pyrobaculum islandicum uses iron, thiosulfate, and elemental sulfur for anaerobic respiration, while Pyrobaculum aerophilum uses iron and nitrate; however, the constraints on these processes and their physiological mechanisms for iron and sulfur reduction are not well understood. Growth rates on sulfur compounds are highest at pH 5 to 6 and highly reduced (<−420-mV) conditions, while growth rates on nitrate and iron are highest at pH 7 to 9 and more-oxidized (>−210-mV) conditions. Growth on iron expands the known pH range of growth for both organisms. P. islandicum differs from P. aerophilum in that it requires direct contact with insoluble iron oxide for growth, it did not produce any extracellular compounds when grown on insoluble iron, and it lacked 2,6-anthrahydroquinone disulfonate oxidase activity. Furthermore, iron reduction in P. islandicum appears to be completely independent of c-type cytochromes. Like that in P. aerophilum, NADH-dependent ferric reductase activity in P. islandicum increased significantly in iron-grown cultures relative to that in non-iron-grown cultures. Proteomic analyses showed that there were significant increases in the amounts of a putative membrane-bound thiosulfate reductase in P. islandicum cultures grown on thiosulfate relative to those in cultures grown on iron and elemental sulfur. This is the first evidence of this enzyme being used in either a hyperthermophile or an archaeon. Pyrobaculum arsenaticum and Pyrobaculum calidifontis also grew on Fe(III) citrate and insoluble iron oxide, but only P. arsenaticum could grow on insoluble iron without direct contact.

scholarly journals Microbe-Mineral Interaction and Novel Proteins for Iron Oxide Mineral Reduction in the Hyperthermophilic Crenarchaeon Pyrodictium delaneyi

2021 ◽  
Author(s):  
Srishti Kashyap ◽  
James F. Holden
Keyword(s):  
Iron Oxide ◽  
Nitrate Reduction ◽  
Direct Contact ◽  
Iron Reduction ◽  
Hyperthermophilic Archaea ◽  
Respiratory Complex ◽  
Oxide Mineral ◽  
Membrane Bound ◽  
Oxide Minerals ◽  
Geothermal Environments

Dissimilatory iron reduction by hyperthermophilic archaea occurs in many geothermal environments and generally relies on microbe-mineral interactions that transform various iron oxide minerals. In this study, the physiology of dissimilatory iron and nitrate reduction was examined in the hyperthermophilic crenarchaeon Pyrodictium delaneyi Su06T. Iron barrier experiments showed that P. delaneyi required direct contact with the Fe(III) oxide mineral ferrihydrite for reduction. The separate addition of an exogenous electron shuttle (anthraquinone-2,6-disulfonate), a metal chelator (nitrilotriacetic acid), and 75% spent cell-free supernatant did not stimulate growth with or without the barrier. Protein electrophoresis showed that the c-type cytochrome and general protein compositions of P. delaneyi changed when grown on ferrihydrite relative to nitrate. Differential proteomic analyses using tandem mass tagged protein fragments and mass spectrometry detected 660 proteins and differential production of 127 proteins. Among these, two putative membrane-bound molybdopterin-dependent oxidoreductase complexes increased in relative abundance 60- to 3,000-fold and 50-100-fold in cells grown on iron oxide. A putative 8-heme c-type cytochrome was 60-fold more abundant in iron grown cells and was unique to the Pyrodictiaceae. There was also a >14,700-fold increase in a membrane transport protein in iron grown cells. There were no changes in the abundances of flagellin proteins nor a putative nitrate reductase, but a membrane nitric oxide reductase was more abundant on nitrate. These data help to elucidate the mechanisms by which hyperthermophilic crenarchaea generate energy and transfer electrons across the membrane to iron oxide minerals. IMPORTANCE Understanding iron reduction in the hyperthermophilic crenarchaeon Pyrodictium delaneyi provides insight into the diversity of mechanisms used for this process and its potential impact in geothermal environments. The ability of P. delaneyi to reduce Fe(III) oxide minerals through direct contact potentially using a novel cytochrome respiratory complex and a membrane-bound molybdopterin respiratory complex sets iron reduction in this organism apart from previously described iron reduction processes. A model is presented where obligatory H2 oxidation on the membrane coupled with electron transport and either Fe(III) oxide or nitrate reduction leads to the generation of a proton motive force and energy generation by oxidative phosphorylation. However, P. delaneyi cannot fix CO2 and relies on organic compounds from its environment for biosynthesis.

scholarly journals Characterization of Dissimilatory Fe(III) versus NO3− Reduction in the Hyperthermophilic Archaeon Pyrobaculum aerophilum

2006 ◽  
Vol 188 (2) ◽  
pp. 525-531 ◽  
Author(s):  
Lawrence F. Feinberg ◽  
James F. Holden
Keyword(s):  
Iron Reduction ◽  
Reductase Activity ◽  
Lag Phase ◽  
Ferric Reductase ◽  
Dialysis Tubing ◽  
Nitrate Medium ◽  
Pyrobaculum Aerophilum ◽  
Hyperthermophilic Archaeon ◽  
Chromatography Analysis ◽  
Cell Extracts

ABSTRACT The hyperthermophilic archaeon Pyrobaculum aerophilum used 20 mM Fe(III) citrate, 100 mM poorly crystalline Fe(III) oxide, and 10 mM KNO3 as terminal electron acceptors. The two forms of iron were reduced at different rates but with equal growth yields. The insoluble iron was reduced when segregated spatially by dialysis tubing, indicating that direct contact with the iron was not necessary for growth. When partitioned, there was no detectable Fe(III) or Fe(II) outside of the tubing after growth, suggesting that an electron shuttle, not a chelator, may be used as an extracellular mediator of iron reduction. The addition of 25 and 50% (vol vol−1) cell-free spent insoluble iron media to fresh media led to growth without a lag phase. Liquid chromatography analysis of spent media showed that cultures grown in iron, especially insoluble iron, produced soluble extracellular compounds that were absent or less abundant in spent nitrate medium. NADH-dependent ferric reductase activity increased approximately 100-fold, while nitrate reductase activity decreased 10-fold in whole-cell extracts from iron-grown cells relative to those from nitrate-grown cells, suggesting that dissimilatory iron reduction was regulated. A novel 2,6-anthrahydroquinone disulfonate oxidase activity was more than 580-fold higher in iron-grown cells than in nitrate-grown cells. The activity was primarily (>95%) associated with the membrane cellular fraction, but its physiological function is unknown. Nitrate-grown cultures produced two membrane-bound, c-type cytochromes that are predicted to be monoheme and part of nitrite reductase and a bc 1 complex using genome analyses. Only one cytochrome was present in cells grown on Fe(III) citrate whose relative abundance was unchanged.

Selective oxidation of hydrogen sulfide to elemental sulfur using iron oxide catalysts on various supports

1993 ◽  
Vol 17 (1-2) ◽  
pp. 217-224 ◽  
Author(s):  
R.J.A.M. Terörde ◽  
P.J. van den Brink ◽  
L.M. Visser ◽  
A.J. van Dillen ◽  
J.W. Geus
Keyword(s):  
Hydrogen Sulfide ◽  
Iron Oxide ◽  
Selective Oxidation ◽  
Elemental Sulfur ◽  
Oxide Catalysts ◽  
Oxidation Of Hydrogen

scholarly journals Anaerobic Respiration of Elemental Sulfur and Thiosulfate by Shewanella oneidensis MR-1 Requires psrA, a Homolog of the phsA Gene of Salmonella enterica Serovar Typhimurium LT2

2009 ◽  
Vol 75 (16) ◽  
pp. 5209-5217 ◽  
Author(s):  
Justin L. Burns ◽  
Thomas J. DiChristina
Keyword(s):  
Gene Cluster ◽  
Salmonella Enterica ◽  
Elemental Sulfur ◽  
Shewanella Oneidensis ◽  
Anaerobic Respiration ◽  
Sulfur Cycle ◽  
Sulfur Compounds ◽  
Electron Acceptors ◽  
Inorganic Sulfur ◽  
Serovar Typhimurium

ABSTRACT Shewanella oneidensis MR-1, a facultatively anaerobic gammaproteobacterium, respires a variety of anaerobic terminal electron acceptors, including the inorganic sulfur compounds sulfite (SO3 2−), thiosulfate (S2O3 2−), tetrathionate (S4O6 2−), and elemental sulfur (S0). The molecular mechanism of anaerobic respiration of inorganic sulfur compounds by S. oneidensis, however, is poorly understood. In the present study, we identified a three-gene cluster in the S. oneidensis genome whose translated products displayed 59 to 73% amino acid similarity to the products of phsABC, a gene cluster required for S0 and S2O3 2− respiration by Salmonella enterica serovar Typhimurium LT2. Homologs of phsA (annotated as psrA) were identified in the genomes of Shewanella strains that reduce S0 and S2O3 2− yet were missing from the genomes of Shewanella strains unable to reduce these electron acceptors. A new suicide vector was constructed and used to generate a markerless, in-frame deletion of psrA, the gene encoding the putative thiosulfate reductase. The psrA deletion mutant (PSRA1) retained expression of downstream genes psrB and psrC but was unable to respire S0 or S2O3 2− as the terminal electron acceptor. Based on these results, we postulate that PsrA functions as the main subunit of the S. oneidensis S2O3 2− terminal reductase whose end products (sulfide [HS−] or SO3 2−) participate in an intraspecies sulfur cycle that drives S0 respiration.

scholarly journals Biocement stabilization of an experimental-scale artificial slope and the reformation of iron-rich crusts

2020 ◽  
Vol 117 (31) ◽  
pp. 18347-18354 ◽  
Author(s):  
Alan Levett ◽  
Emma J. Gagen ◽  
Yitian Zhao ◽  
Paulo M. Vasconcelos ◽  
Gordon Southam
Keyword(s):  
Iron Oxide ◽  
Iron Ore ◽  
Iron Reduction ◽  
Control Experiment ◽  
Mine Waste ◽  
Carbon Sources ◽  
Waste Stabilization ◽  
The Reformation ◽  
Mine Remediation ◽  
Reduction And Oxidation

Novel biotechnologies are required to remediate iron ore mines and address the increasing number of tailings (mine waste) dam collapses worldwide. In this study, we aimed to accelerate iron reduction and oxidation to stabilize an artificial slope. An open-air bioreactor was inoculated with a mixed consortium of microorganisms capable of reducing iron. Fluid from the bioreactor was allowed to overflow onto the artificial slope. Carbon sources from the bioreactor fluid promoted the growth of a surface biofilm within the artificial slope, which naturally aggregated the crushed grains. The biofilms provided an organic framework for the nucleation of iron oxide minerals. Iron-rich biocements stabilized the artificial slope and were significantly more resistant to physical deformation compared with the control experiment. These biotechnologies highlight the potential to develop strategies for mine remediation and waste stabilization by accelerating the biogeochemical cycling of iron.

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.

scholarly journals Genetic Analysis of Trimethylamine N-Oxide Reductases in the Light Organ Symbiont Vibrio fischeri ES114

2008 ◽  
Vol 190 (17) ◽  
pp. 5814-5823 ◽  
Author(s):  
Anne K. Dunn ◽  
Eric V. Stabb
Keyword(s):  
Vibrio Fischeri ◽  
Reductase Activity ◽  
Anaerobic Respiration ◽  
Gene Arrangement ◽  
Light Organ ◽  
Euprymna Scolopes ◽  
Light Organs ◽  
Dependent Growth ◽  
Tmao Reductase ◽  
Active Promoter

ABSTRACT Trimethylamine N-oxide (TMAO) reductases are widespread in bacteria and often function in anaerobic respiration. The regulation and expression of TMAO reductase operons have been well studied in model genera such as Escherichia, Shewanella, and Rhodobacter, although TMAO reductases are present in many other bacteria, including the marine Vibrio species. The genome sequence of Vibrio fischeri revealed three putative TMAO reductase operons, and a previous report identified TMAO reductase activity in symbiotic V. fischeri isolates associated with the light organs of adult Hawaiian bobtail squid, Euprymna scolopes. We examined the roles and regulation of these three operons using mutational analyses and promoter-reporter fusions. We found that the torECA promoter, and to a lesser extent the torYZ and dmsABC promoters, were active during symbiotic colonization of juvenile E. scolopes; however, a V. fischeri strain lacking TMAO reductase activity displays no discernible colonization defect over the first 48 h. Our studies also revealed that torECA has the most active promoter of the putative TMAO reductase operons, and TorECA is the major contributor to TMAO-dependent growth in V. fischeri under the conditions tested. Interestingly, the transcriptional regulation of TMAO reductase operons in V. fischeri appears to differ from that in previously studied organisms, such as Escherichia coli, which may reflect differences in gene arrangement and bacterial habitat. This study lays the foundation for using V. fischeri as a model system for studying TMAO reductases in the Vibrionaceae.

scholarly journals Key Role for Sulfur in Peptide Metabolism and in Regulation of Three Hydrogenases in the Hyperthermophilic ArchaeonPyrococcus furiosus

2001 ◽  
Vol 183 (2) ◽  
pp. 716-724 ◽  
Author(s):  
Michael W. W. Adams ◽  
James F. Holden ◽  
Angeli Lal Menon ◽  
Gerrit J. Schut ◽  
Amy M. Grunden ◽  
...  
Keyword(s):  
Growth Rates ◽  
Elemental Sulfur ◽  
Pyrococcus Furiosus ◽  
Growth Conditions ◽  
Growth Media ◽  
Hyperthermophilic Archaeon ◽  
Order Of Magnitude ◽  
Membrane Bound ◽  
Peptide Metabolism ◽  
Specific Activities

ABSTRACT The hyperthermophilic archaeon Pyrococcus furiosusgrows optimally at 100°C by the fermentation of peptides and carbohydrates. Growth of the organism was examined in media containing either maltose, peptides (hydrolyzed casein), or both as the carbon source(s), each with and without elemental sulfur (S0). Growth rates were highest on media containing peptides and S0, with or without maltose. Growth did not occur on the peptide medium without S0. S0 had no effect on growth rates in the maltose medium in the absence of peptides. Phenylacetate production rates (from phenylalanine fermentation) from cells grown in the peptide medium containing S0 with or without maltose were the same, suggesting that S0 is required for peptide utilization. The activities of 14 of 21 enzymes involved in or related to the fermentation pathways of P. furiosus were shown to be regulated under the five different growth conditions studied. The presence of S0 in the growth media resulted in decreases in specific activities of two cytoplasmic hydrogenases (I and II) and of a membrane-bound hydrogenase, each by an order of magnitude. The primary S0-reducing enzyme in this organism and the mechanism of the S0 dependence of peptide metabolism are not known. This study provides the first evidence for a highly regulated fermentation-based metabolism in P. furiosus and a significant regulatory role for elemental sulfur or its metabolites.

Sulfur Oxidation and Coupled Iron Reduction at Low Temperatures

2007 ◽  
Vol 20-21 ◽  
pp. 584-584 ◽  
Author(s):  
Daniel Kupka ◽  
Mark Dopson ◽  
Olli H. Tuovinen
Keyword(s):  
Acidithiobacillus Ferrooxidans ◽  
Low Temperatures ◽  
Iron Reduction ◽  
Elemental Sulfur ◽  
Surface Soil ◽  
Sulfur Oxidation ◽  
Oxygen Limitation ◽  
Northern Siberia ◽  
Elemental Sulfur Oxidation

The purpose of this work was to characterize elemental sulfur oxidation by a psychrotrophic Acidithiobacillus ferrooxidans culture that originated from an AMD-impacted surface soil in a permafrost area in northern Siberia. In this work, the iron-oxidizing culture was cultivated with elemental sulfur with and without Fe2+ or Fe3+ in flasks on a shaker to avoid oxygen limitation.

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