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

Kučera, Jiří; Pakostová, Eva; Lochman, Jan; Janiczek, Oldřich; Mandl, Martin

doi:10.1016/j.resmic.2016.02.004

Cited by 28 publications

(30 citation statements)

References 47 publications

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“…The phenotypes of 33-X, 33-R1, and 33-R2 strongly suggest that, at least in A. ferridurans T , the electrons could be transferred from CycA2 to rusticyanin and from there to the outer membrane cytochrome c Cyc2, where ferric iron reduction could occur (Fig. 5), as proposed elsewhere (23).…”

Section: Discussionsupporting

confidence: 73%

“…Therefore, these data indicate that one or more of the redox proteins encoded by the rus operon are involved both in ferrous iron oxidation and in ferric iron reduction. Two different mechanisms of anaerobic sulfur oxidation coupled to ferric iron reduction have been proposed in A. ferrooxidans, one in the type strain (ATCC 23270 T [22]) and another in strain CCM 4253 (23,24). In the model proposed for A. ferrooxidans T , the electrons flow from sulfur to quinone and onwards to the bc 1 complex and then to CycA2, these redox proteins being encoded by the petII operon.…”

Section: Discussionmentioning

confidence: 99%

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Salt Stress-Induced Loss of Iron Oxidoreduction Activities and Reacquisition of That Phenotype Depend on rus Operon Transcription in Acidithiobacillus ferridurans

Bonnefoy

Grail

Johnson

2018

Appl Environ Microbiol

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The type strain of the mineral-oxidizing acidophilic bacterium was grown in liquid medium containing elevated concentrations of sodium chloride with hydrogen as electron donor. While it became more tolerant to chloride, after about 1 year, the salt-stressed acidophile was found to have lost its ability to oxidize iron, though not sulfur or hydrogen. Detailed molecular examination revealed that this was due to an insertion sequence, IS, which belongs to the IS subgroup of the IS family, having been inserted downstream of the two promoters PI and PII of the operon (which codes for the iron oxidation pathway in this acidophile), thereby preventing its transcription. The ability to oxidize iron was regained on protracted incubation of the culture inoculated onto salt-free solid medium containing ferrous iron and incubated under hydrogen. Two revertant strains were obtained. In one, the insertion sequence IS had been excised, leaving an 11-bp signature, while in the other an ∼2,500-bp insertion sequence (belonging to the IS family) was detected in the downstream inverted repeat of IS The transcriptional start site of the operon in the second revertant strain was downstream of the two ISs, due to the creation of a new "hybrid" promoter. The loss and subsequent regaining of the ability of to reduce ferric iron were concurrent with those observed for ferrous iron oxidation, suggesting that these two traits are closely linked in this acidophile. Iron-oxidizing acidophilic bacteria have primary roles in the oxidative dissolution of sulfide minerals, a process that underpins commercial mineral-processing biotechnologies ("biomining"). Most of these prokaryotes have relatively low tolerance to chloride, which limits their activities when only saline or brackish waters are available. The study showed that it was possible to adapt a typical iron-oxidizing acidophile to grow in the presence of salt concentrations similar to those in seawater, but in so doing they lost their ability to oxidize iron, though not sulfur or hydrogen. The bacterium regained its capacity for oxidizing iron when the salt stress was removed but simultaneously reverted to tolerating lower concentrations of salt. These results suggest that the bacteria that have the main roles in biomining operations could survive but become ineffective in cases where saline or brackish waters are used for irrigation.

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Section: Discussionsupporting

confidence: 73%

Section: Discussionmentioning

confidence: 99%

Salt Stress-Induced Loss of Iron Oxidoreduction Activities and Reacquisition of That Phenotype Depend on rus Operon Transcription in Acidithiobacillus ferridurans

Bonnefoy

Grail

Johnson

2018

Appl Environ Microbiol

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“…In line with this conclusion, it was recently proposed that Cyt c 4 from A. ferrooxidans would be involved in the anaerobic electron transfer chain coupling Fe 3+ reduction to sulfur oxidation. 41 In such a case, Cyt c 4 would transfer electrons to other partners than C c O. Interestingly, versatility has also been demonstrated recently using the diheme cytochrome c 550 from Thermus thermophilus . 42 Whether it is a general property of diheme cytochromes is an interesting open question.…”

Section: Resultsmentioning

confidence: 96%

Electron transfer in an acidophilic bacterium: interaction between a diheme cytochrome and a cupredoxin

et al. 2018

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“…Total RNA was isolated from three biological replicates of 200 mL using the TRI Reagent (Sigma-Aldrich) and DNA was removed using DNase I (Thermo Scientific) according to the manufacturer’s guidelines. The expression of the selected genes (the tetrathionate hydrolase tetH , the subunit d oxDA of the thiosulfate-quinone oxidoreductase complex, and the subunit hdrA of the heterodisulfide oxidoreductase complex) involved in energy metabolism of reduced inorganic sulfur compounds was determined by RT-qPCR as previously described (Kucera et al, 2013) using gene-specific oligonucleotides, the sequences of which were shown earlier (Kucera et al, 2016). The relative expression level ( R ) of each gene was normalized using the housekeeping gene ( alaS ) to facilitate evaluation of gene expression in relation to the internal standard by the ΔΔCT method (Pfaffl, 2001; Nieto et al, 2009).…”

Section: Methodsmentioning

confidence: 99%

Can Sulfate Be the First Dominant Aqueous Sulfur Species Formed in the Oxidation of Pyrite by Acidithiobacillus ferrooxidans?

et al. 2018

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According to the literature, pyrite (FeS2) oxidation has been previously determined to involve thiosulfate as the first aqueous intermediate sulfur product, which is further oxidized to sulfate. In the present study, pyrite oxidation by Acidithiobacillus ferrooxidans was studied using electrochemical and metabolic approaches in an effort to extend existing knowledge on the oxidation mechanism. Due to the small surface area, the reaction rate of a compact pyrite electrode in the form of polycrystalline pyrite aggregate in A. ferrooxidans suspension was very slow at a spontaneously formed high redox potential. The slow rate made it possible to investigate the oxidation process in detail over a term of 100 days. Using electrochemical parameters from polarization curves and levels of released iron, the number of exchanged electrons per pyrite molecule was estimated. The values close to 14 and 2 electrons were determined for the oxidation with and without bacteria, respectively. These results indicated that sulfate was the dominant first aqueous sulfur species formed in the presence of bacteria and elemental sulfur was predominantly formed without bacteria. The stoichiometric calculations are consistent with high iron-oxidizing activities of bacteria that continually keep the released iron in the ferric form, resulting in a high redox potential. The sulfur entity of pyrite was oxidized to sulfate by Fe3+ without intermediate thiosulfate under these conditions. Cell attachment on the corroded pyrite electrode surface was documented although pyrite surface corrosion by Fe3+ was evident without bacterial participation. Attached cells may be important in initiating the oxidation of the pyrite surface to release iron from the mineral. During the active phase of oxidation of a pyrite concentrate sample, the ATP levels in attached and planktonic bacteria were consistent with previously established ATP content of iron-oxidizing cells. No significant upregulation of three essential genes involved in energy metabolism of sulfur compounds was observed in the planktonic cells, which represented the dominant biomass in the pyrite culture. The study demonstrated the formation of sulfate as the first dissolved sulfur species with iron-oxidizing bacteria under high redox potential conditions. Minor aqueous sulfur intermediates may be formed but as a result of side reactions.

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

Cited by 28 publications

References 47 publications

Salt Stress-Induced Loss of Iron Oxidoreduction Activities and Reacquisition of That Phenotype Depend on rus Operon Transcription in Acidithiobacillus ferridurans

Salt Stress-Induced Loss of Iron Oxidoreduction Activities and Reacquisition of That Phenotype Depend on rus Operon Transcription in Acidithiobacillus ferridurans

Electron transfer in an acidophilic bacterium: interaction between a diheme cytochrome and a cupredoxin

Can Sulfate Be the First Dominant Aqueous Sulfur Species Formed in the Oxidation of Pyrite by Acidithiobacillus ferrooxidans?

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