Involvement of Iron Oxidation Enzyme System in Sulfur Oxidation of <i>Acidithiobacillus ferrooxidans</i> ATCC 23270

The acidophilic and strictly chemolithoautotrophic bacterium Acidithiobacillus ferrooxidans oxidizes ferrous (Fe(II)) to ferric (Fe(III)) iron and reduced inorganic sulfur compounds (RISC) to sulfuric acid, in oxic conditions. The redox proteins involved in the electron transfer between Fe(II) and oxygen are encoded in the same transcriptional unit, the rus operon. The expression of this operon is induced in the presence of Fe(II), but not Fe(III), and is not repressed in the presence of sulfur (S0). A number of genes differentially expressed in iron or sulfur conditions have been identified by microarrays transcript profiling. We show here that the presence of Fe(II) induced the expression of the genes involved in iron oxidation and repressed the expression of the genes involved in RISC oxidation. Identification of the regulator(s) involved in this transcriptional regulation is underway. Two genes encoding putative regulators belonging to two transcriptional units located downstream from the rus operon have been cloned. One regulator with a putative ironsulfur cluster belongs to the IscR family and the other belongs to the two component sensor/regulator family. Expression of both genes is induced in the presence of Fe(II) and is not repressed by S0. The recombinant proteins have been purified and gel shift assays with the target regulatory regions are in progress.

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Dispersion of sulfur enables sulfur oxidation before iron oxidation in Acidithiobacillus ferrooxidans: A valuable formulation for the genetic engineering toolbox

10.22541/au.161486164.44901503/v1 ◽

2021 ◽

Author(s):

Yuta Inaba ◽

Timothy Kernan ◽

Alan West ◽

Scott Banta

Keyword(s):

Acidithiobacillus Ferrooxidans ◽

Ferrous Iron ◽

Iron Reduction ◽

Fluorescent Protein ◽

Energy Content ◽

Iron Oxidation ◽

Sulfur Oxidation ◽

Surface Hydrophobicity ◽

Substrate Utilization Pattern ◽

Ferrous Iron Oxidation

Acidithiobacillus ferrooxidans are acidophilic chemolithoautotrophs that are commonly reported to exhibit diauxic population growth behavior where ferrous iron is oxidized before elemental sulfur when both are available, despite the higher energy content of sulfur. We have discovered sulfur dispersion formulations that enables sulfur oxidation before ferrous iron oxidation. The oxidation of dispersed sulfur can lower the culture pH within days below the range where aerobic ferrous iron oxidation can occur so that ferric iron reduction occurs which had previously been reported over extended incubation periods with untreated sulfur. Therefore, we demonstrate that this substrate utilization pattern is strongly dependent on the cell loading in relation to sulfur concentration, sulfur surface hydrophobicity, and the pH of the culture. Our dispersed sulfur formulation, lig-sulfur, can be used to support the rapid antibiotic selection of plasmid-transformed cells, which is not possible in liquid cultures where ferrous iron is the main source of energy for these acidophiles. Furthermore, we find that media containing lig-sulfur supports higher production of green fluorescent protein (GFP) compared to media containing ferrous iron. The use of dispersed sulfur is a valuable new tool for the development of engineered A. ferrooxidans strains and it provides a new method to control iron and sulfur oxidation behaviors.

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Dispersion of sulfur creates a valuable new growth medium formulation that enables earlier sulfur oxidation in relation to iron oxidation in Acidithiobacillus ferrooxidans cultures

Biotechnology and Bioengineering ◽

10.1002/bit.27847 ◽

2021 ◽

Author(s):

Yuta Inaba ◽

Timothy Kernan ◽

Alan C. West ◽

Scott Banta

Keyword(s):

Growth Medium ◽

Acidithiobacillus Ferrooxidans ◽

Iron Oxidation ◽

Sulfur Oxidation ◽

Medium Formulation

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Involvement of Iron Oxidation Enzyme System in Sulfur Oxidation of Acidithiobacillus ferrooxidans ATCC 23270

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.20-21.443 ◽

2007 ◽

Vol 20-21 ◽

pp. 443-446 ◽

Cited By ~ 4

Author(s):

Taher M. Taha ◽

Tadayoshi Kanao ◽

Fumiaki Takeuchi ◽

Tsuyoshi Sugio

Keyword(s):

Oxidase Activity ◽

Plasma Membranes ◽

Cultured Cells ◽

Enzyme System ◽

Iron Oxidation ◽

Growth Yield ◽

Maximum Growth ◽

Ferric Sulfate ◽

Lag Phase ◽

Oxidation Enzyme

Growth of A. ferrooxidans ATCC 23270 cells in sulfur medium with 0.005% ferric sulfate for 3, 4, 5, 6, 7 and 10 days gave the maximum growth yield of 45, 58, 76, 86, 90 and 95 mg protein per liter medium, respectively. Iron oxidase activities of 1-, 2- and 3- day-cultured cells on sulfur with 0.005% ferric sulfate (3.4, 3.5 and 0.8 μmol Fe2+ oxidized/mg protein/min) were approximately 68, 70 and 16% of iron-grown ATCC 23270 cells (5.0 μmol/mg protein/min). In contrast iron oxidase activities of 1-, 2- and 3-day cultured cells on sulfur without iron (4.9, 3.8 and 2.7 μmol Fe2+ oxidized/mg protein/min) were approximately 98, 76 and 54% of the iron oxidase activity observed in iron-grown ATCC 23270 cell. SFORase activities of 3 day-cultured cell on sulfur with and without ferric sulfate (0.62 and 0.31 μmol Fe2+ produced/mg protein/min) were approximately 20 and 10 fold higher than that of iron-grown cell (0.03 μmol Fe2+ produced/mg protein/min). Both iron oxidase and SFORase activities increased at early-log phase and decreased at late-lag phase during growth of the strain on sulfur with or without Fe3+. The plasma membranes which had iron oxidase activity were prepared not only from iron-grown cells but also sulfur-grown cells. Iron oxidase activities of the plasma membranes prepared from sulfur- and iron-grown cells were 3.6 and 4.5 nmol Fe2+ oxidized per mg protein per min. These results suggest that iron oxidation enzyme system has a role in part in the energy generation of this bacterium from sulfur.

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How the RegBA Redox Responding System Controls Iron and Sulfur Oxidation in Acidithiobacillus ferrooxidans

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.825.186 ◽

2013 ◽

Vol 825 ◽

pp. 186-189 ◽

Cited By ~ 3

Author(s):

Danielle Moinier ◽

Deborah Byrne ◽

Agnès Amouric ◽

Violaine Bonnefoy

Keyword(s):

Acidithiobacillus Ferrooxidans ◽

Ferrous Iron ◽

Iron Oxidation ◽

Regulatory Region ◽

Sulfur Oxidation ◽

Sulfur Compounds ◽

Chemical Attack ◽

Valuable Metals ◽

Genes Encoding ◽

Iron And Sulfur Oxidation

Valuable metals as well as ferrous iron and sulfur compounds are released from ore by ferric iron and sulfuric acid chemical attack. Biomining microorganisms allow the recycling of these products by oxidizing ferrous iron and/or sulfur compounds. The energy released from the oxidation of these substrates is used for the growth of the acidophilic chemolithoautotrophic bacterium Acidithiobacillus ferrooxidans. The respiratory pathways involved in these respiratory processes have been deciphered and the expression of the genes encoding these redox proteins is dependent on the electron donor present in the medium. Furthermore, in the presence of both ferrous iron and sulfur, the genes involved in iron oxidation are expressed before those involved in sulfur oxidation. We propose that the global redox responding two component system RegBA is responsible for this regulation since (i) the redox potential increases during iron oxidation but remains stable during sulfur oxidation and (ii) the transcriptional regulator RegA binds the regulatory region of a number of genes/operons involved in iron and sulfur oxidation. To understand the mechanism of the At. ferrooxidans RegBA system, the regA gene and the DNA corresponding to the DNA binding domain of RegA were cloned in an expression plasmid in Escherichia coli. The recombinant proteins, RegA and RegA-HTH respectively, were purified. The binding of RegA-HTH, phosphorylated and unphosphorylated RegA on the regulatory region of some target operons have been compared by gel shift mobility assay.

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

Water Science & Technology ◽

10.2166/wst.2002.0456 ◽

2002 ◽

Vol 46 (1-2) ◽

pp. 55-60 ◽

Cited By ~ 1

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.

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Are there multiple mechanisms of anaerobic sulfur oxidation with ferric iron in Acidithiobacillus ferrooxidans ?

Research in Microbiology ◽

10.1016/j.resmic.2016.02.004 ◽

2016 ◽

Vol 167 (5) ◽

pp. 357-366 ◽

Cited By ~ 15

Author(s):

Jiri Kucera ◽

Eva Pakostova ◽

Jan Lochman ◽

Oldrich Janiczek ◽

Martin Mandl

Keyword(s):

Acidithiobacillus Ferrooxidans ◽

Ferric Iron ◽

Sulfur Oxidation ◽

Anaerobic Sulfur Oxidation

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A kinetic model of ferrous iron oxidation by Acidithiobacillus ferrooxidans in a batch culture

Chemical Industry and Chemical Engineering Quarterly ◽

10.2298/ciceq0502059s ◽

2005 ◽

Vol 11 (2) ◽

pp. 59-62 ◽

Cited By ~ 5

Author(s):

Dragisa Savic ◽

Miodrag Lazic ◽

Vlada Veljkovic ◽

Miroslav Vrvic

Keyword(s):

Kinetic Model ◽

Acidithiobacillus Ferrooxidans ◽

Ferrous Iron ◽

Bubble Column ◽

Iron Oxidation ◽

Yield Coefficient ◽

Transfer Rates ◽

Ferrous Iron Oxidation ◽

Menten Kinetic ◽

Kinetics Of

The batch oxidation kinetics of ferrous iron by Acidithiobacillus ferrooxidans were examined at different oxygen transfer rates and pH in an aerated stirred tank and a bubble column. The microbial growth, oxygen consumption rate and ferrous and ferric iron were monitored during the biooxidation. A kinetic model was established on the basis of the Michaelis-Menten kinetic equation for bacterial growth and the constants estimated from experimental data (maximum specific growth rate 0.069 h-1, saturation constant 2.9 g/dm3, and biomass yield coefficient based on ferrous iron 0.003 gd.w./gFe). Values calculated from the model agreed well with the experimental ones regardless of the bioreactor type and pH conditions.

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