scholarly journals Mimicking the Microbial Oxidation of Elemental Sulfur with a Biphasic Electrochemical Cell

Author(s):  
Marco F. Suárez-Herrera ◽  
Jose Solla-Gullon ◽  
Micheal D. Scanlon

<p>The lack of an artificial system that mimics elemental sulfur (S<sub>8</sub>) oxidation by microorganisms inhibits a deep mechanistic understanding of the sulfur cycle in the biosphere and the metabolism of sulfur-oxidizing microorganisms. In this article, we present a biphasic system that mimics biochemical sulfur oxidation under ambient conditions using a liquid|liquid (L|L) electrochemical cell and gold nanoparticles (AuNPs) as an interfacial catalyst. The interface between two solvents of very different polarity is an ideal environment to oxidise S<sub>8</sub>, overcoming the <a>incompatible solubilities </a>of the hydrophobic reactants (O<sub>2</sub> and S<sub>8</sub>) and hydrophilic products (H<sup>+</sup>, SO<sub>3</sub><sup>2–</sup>, SO<sub>4</sub><sup>2–</sup>, <i>etc.</i>). The interfacial AuNPs provide a catalytic surface onto which O<sub>2</sub> and S<sub>8</sub> can adsorb. Control over the driving force for the reaction is provided by polarizing the L|L interface externally and tuning the Fermi level of the interfacial AuNPs by the adsorption of aqueous anions.</p>

2021 ◽  
Author(s):  
Marco F. Suárez-Herrera ◽  
Jose Solla-Gullon ◽  
Micheal D. Scanlon

<p>The lack of an artificial system that mimics elemental sulfur (S<sub>8</sub>) oxidation by microorganisms inhibits a deep mechanistic understanding of the sulfur cycle in the biosphere and the metabolism of sulfur-oxidizing microorganisms. In this article, we present a biphasic system that mimics biochemical sulfur oxidation under ambient conditions using a liquid|liquid (L|L) electrochemical cell and gold nanoparticles (AuNPs) as an interfacial catalyst. The interface between two solvents of very different polarity is an ideal environment to oxidise S<sub>8</sub>, overcoming the <a>incompatible solubilities </a>of the hydrophobic reactants (O<sub>2</sub> and S<sub>8</sub>) and hydrophilic products (H<sup>+</sup>, SO<sub>3</sub><sup>2–</sup>, SO<sub>4</sub><sup>2–</sup>, <i>etc.</i>). The interfacial AuNPs provide a catalytic surface onto which O<sub>2</sub> and S<sub>8</sub> can adsorb. Control over the driving force for the reaction is provided by polarizing the L|L interface externally and tuning the Fermi level of the interfacial AuNPs by the adsorption of aqueous anions.</p>


2004 ◽  
Vol 70 (5) ◽  
pp. 3122-3129 ◽  
Author(s):  
Tsukasa Ito ◽  
Kenichi Sugita ◽  
Satoshi Okabe

ABSTRACT We successfully isolated a novel aerobic chemolithotrophic sulfur-oxidizing bacterium, designated strain SO07, from wastewater biofilms growing under microaerophilic conditions. For isolation, the use of elemental sulfur (S0), which is the most abundant sulfur pool in the wastewater biofilms, as the electron donor was an effective measure to establish an enrichment culture of strain SO07 and further isolation. 16S rRNA gene sequence analysis revealed that newly isolated strain SO07 was affiliated with members of the genus Halothiobacillus, but it was only distantly related to previously isolated species (89% identity). Strain SO07 oxidized elemental sulfur, thiosulfate, and sulfide to sulfate under oxic conditions. Strain SO07 could not grow on nitrate. Organic carbons, including acetate, propionate, and formate, could not serve as carbon and energy sources. Unlike other aerobic sulfur-oxidizing bacteria, this bacterium was sensitive to NaCl; growth in medium containing more than 150 mM was negligible. In situ hybridization combined with confocal laser scanning microscopy revealed that a number of rod-shaped cells hybridized with a probe specific for strain SO07 were mainly present in the oxic biofilm strata (ca. 0 to 100 μm) and that they often coexisted with sulfate-reducing bacteria in this zone. These results demonstrated that strain SO07 was one of the important sulfur-oxidizing populations involved in the sulfur cycle occurring in the wastewater biofilm and was primarily responsible for the oxidation of H2S and S0 to SO4 2− under oxic conditions.


mBio ◽  
2014 ◽  
Vol 5 (1) ◽  
Author(s):  
Huiluo Cao ◽  
Yong Wang ◽  
On On Lee ◽  
Xiang Zeng ◽  
Zongze Shao ◽  
...  

ABSTRACT Sulfur is an important element in sustaining microbial communities present in hydrothermal vents. Sulfur oxidation has been extensively studied due to its importance in chemosynthetic pathways in hydrothermal fields; however, less is known about sulfate reduction. Here, the metagenomes of hydrothermal chimneys located on the ultraslow-spreading Southwest Indian Ridge (SWIR) were pyrosequenced to elucidate the associated microbial sulfur cycle. A taxonomic summary of known genes revealed a few dominant bacteria that participated in the microbial sulfur cycle, particularly sulfate-reducing Deltaproteobacteria. The metagenomes studied contained highly abundant genes related to sulfur oxidation and reduction. Several carbon metabolic pathways, in particular the Calvin-Benson-Bassham pathway and the reductive tricarboxylic acid cycles for CO2 fixation, were identified in sulfur-oxidizing autotrophic bacteria. In contrast, highly abundant genes related to the oxidation of short-chain alkanes were grouped with sulfate-reducing bacteria, suggesting an important role for short-chain alkanes in the sulfur cycle. Furthermore, sulfur-oxidizing bacteria were associated with enrichment for genes involved in the denitrification pathway, while sulfate-reducing bacteria displayed enrichment for genes responsible for hydrogen utilization. In conclusion, this study provides insights regarding major microbial metabolic activities that are driven by the sulfur cycle in low-temperature hydrothermal chimneys present on an ultraslow midocean ridge. IMPORTANCE There have been limited studies on chimney sulfides located at ultraslow-spreading ridges. The analysis of metagenomes of hydrothermal chimneys on the ultraslow-spreading Southwest Indian Ridge suggests the presence of a microbial sulfur cycle. The sulfur cycle should be centralized within a microbial community that displays enrichment for sulfur metabolism-related genes. The present study elucidated a significant role of the microbial sulfur cycle in sustaining an entire microbial community in low-temperature hydrothermal chimneys on an ultraslow spreading midocean ridge, which has characteristics distinct from those of other types of hydrothermal fields.


2015 ◽  
Vol 81 (9) ◽  
pp. 3142-3156 ◽  
Author(s):  
Daniel S. Jones ◽  
Beverly E. Flood ◽  
Jake V. Bailey

ABSTRACTLarge sulfur-oxidizing bacteria in the familyBeggiatoaceaeare important players in the global sulfur cycle. This group contains members of the well-known generaBeggiatoa,Thioploca, andThiomargaritabut also recently identified and relatively unknown candidate taxa, including “CandidatusThiopilula” spp. and “Ca. Thiophysa” spp. We discovered a population of “Ca. Thiopilula” spp. colonizing cold seeps near Barbados at a ∼4.7-km water depth. The Barbados population consists of spherical cells that are morphologically similar toThiomargaritaspp., with elemental sulfur inclusions and a central vacuole, but have much smaller cell diameters (5 to 40 μm). Metatranscriptomic analysis revealed that when exposed to anoxic sulfidic conditions, Barbados “Ca. Thiopilula” organisms expressed genes for the oxidation of elemental sulfur and the reduction of nitrogenous compounds, consistent with their vacuolated morphology and intracellular sulfur storage capability. Metatranscriptomic analysis further revealed that anaerobic methane-oxidizing and sulfate-reducing organisms were active in the sediment, which likely provided reduced sulfur substrates for “Ca. Thiopilula” and other sulfur-oxidizing microorganisms in the community. The novel observations of “Ca. Thiopilula” and associated organisms reported here expand our knowledge of the globally distributed and ecologically successfulBeggiatoaceaegroup and thus offer insight into the composition and ecology of deep cold seep microbial communities.


Pedosphere ◽  
2010 ◽  
Vol 20 (1) ◽  
pp. 71-79 ◽  
Author(s):  
Zhi-Hui YANG ◽  
K. STÖVEN ◽  
S. HANEKLAUS ◽  
B.R. SINGH ◽  
E. SCHNUG

Microbiology ◽  
2003 ◽  
Vol 149 (7) ◽  
pp. 1699-1710 ◽  
Author(s):  
Thore Rohwerder ◽  
Wolfgang Sand

To identify the actual substrate of the glutathione-dependent sulfur dioxygenase (EC 1.13.11.18) elemental sulfur oxidation of the meso-acidophilic Acidithiobacillus thiooxidans strains DSM 504 and K6, Acidithiobacillus ferrooxidans strain R1 and Acidiphilium acidophilum DSM 700 was analysed. Extraordinarily high specific sulfur dioxygenase activities up to 460 nmol min−1 (mg protein)−1 were found in crude extracts. All cell-free systems oxidized elemental sulfur only via glutathione persulfide (GSSH), a non-enzymic reaction product from glutathione (GSH) and elemental sulfur. Thus, GSH plays a catalytic role in elemental sulfur activation, but is not consumed during enzymic sulfane sulfur oxidation. Sulfite is the first product of sulfur dioxygenase activity; it further reacted non-enzymically to sulfate, thiosulfate or glutathione S-sulfonate (). Free sulfide was not oxidized by the sulfur dioxygenase. Persulfide as sulfur donor could not be replaced by other sulfane-sulfur-containing compounds (thiosulfate, polythionates, bisorganyl-polysulfanes or monoarylthiosulfonates). The oxidation of H2S by the dioxygenase required GSSG, i.e. the disulfide of GSH, which reacted non-enzymically with sulfide to give GSSH prior to enzymic oxidation. On the basis of these results and previous findings a biochemical model for elemental sulfur and sulfide oxidation in Acidithiobacillus and Acidiphilium spp. is proposed.


1988 ◽  
Vol 68 (3) ◽  
pp. 475-483 ◽  
Author(s):  
J. R. LAWRENCE ◽  
V. V. S. R. GUPTA ◽  
J. J. GERMIDA

Effects of elemental sulfur fertilization on sulfur-oxidizing populations, rhodanese activity, total sulfur content and sulfur oxidation rates in the 0- to 15-cm zone of two Grey Luvisolic soils were assessed. Heterotrophic sulfur oxidizers were the most abundant sulfur oxidizers detected in both soils. Elemental sulfur fertilization caused an increase in populations of autotrophic thiosulfate-oxidizing micro-organisms, and a threefold increase in rhodanese and sulfur-oxidizing activity in a Waitville soil. In contrast, sulfur fertilization did not stimulate autotrophic thiosulfate oxidizers in a Loon River soil and the greatest increase in rhodanese and sulfur oxidation rates was only 31%. The response to sulfur application was biphasic however, and subsequent additions of sulfur fertilizer resulted in a decline in oxidation rates. Total sulfur content of sulfur-treated soils indicated that most of the sulfur applied was still present in the sampled zone. These results imply that prediction of sulfate release and fertilizer efficiency will be difficult to assess. Key words: Sulfur (elemental), S-oxidation, oxidation rates, rhodanese, sulfur-oxidizing micro-organisms


1991 ◽  
Vol 71 (1) ◽  
pp. 127-136 ◽  
Author(s):  
J. R. Lawrence ◽  
J.J. Germida

Heterotrophic and autotrophic sulfur-oxidizing populations in 35 Saskatchewan agricultural soils were enumerated. These populations included heterotrophs that produce thiosulfate and or sulfate during elemental sulfur (S°) oxidation, heterotrophic thiosulfate oxidizers, and autotrophic thiosulfate oxidizers. Populations of Thiobacillus thiooxidans and T. ferrooxidans were not detected in any of the soils tested. Heterotrophs that oxidized S° to thiosulfate as the major oxyanion were the most abundant oxidizers enumerated (107–108 cells g−1) and were found in all soils. Autotrophic thiosulfate-oxidizers were detected in 10 of the soils surveyed. Heterotrophic S° and thiosulfate-oxidizing populations exhibited positive trends with soil pH, total-S, hydriodic reducible-S, and clay content, whereas populations of autotrophic thiosulfate oxidizers were negatively correlated with these factors and positively related to sand content and increasing C:S ratios. In soils containing autotrophic thiosulfate oxidizers the amount of thiosulfate relative to sulfate detected was reduced although no effect on S° oxidation rate was detected. Amendment of 15 selected agricultural soils with 0.5% S° significantly reduced total heterotrophic populations, whereas autotrophic thiosulfate oxidizers increased from undetectable levels to 104 cells g−1. Therefore most Saskatchewan soils contain abundant populations of heterotrophic S° oxidizers, and populations of autotrophs that respond to S° applications. Key words: Sulfur oxidation, autotrophic sulfur oxidizers, heterotrophic sulfur oxidizers, soil properties


Microbiology ◽  
2014 ◽  
Vol 160 (1) ◽  
pp. 123-129 ◽  
Author(s):  
Tian Zhang ◽  
Timothy S. Bain ◽  
Melissa A. Barlett ◽  
Shabir A. Dar ◽  
Oona L. Snoeyenbos-West ◽  
...  

Microbial oxidation of elemental sulfur with an electrode serving as the electron acceptor is of interest because this may play an important role in the recovery of electrons from sulfidic wastes and for current production in marine benthic microbial fuel cells. Enrichments initiated with a marine sediment inoculum, with elemental sulfur as the electron donor and a positively poised (+300 mV versus Ag/AgCl) anode as the electron acceptor, yielded an anode biofilm with a diversity of micro-organisms, including Thiobacillus, Sulfurimonas, Pseudomonas, Clostridium and Desulfuromonas species. Further enrichment of the anode biofilm inoculum in medium with elemental sulfur as the electron donor and Fe(III) oxide as the electron acceptor, followed by isolation in solidified sulfur/Fe(III) medium yielded a strain of Desulfuromonas, designated strain TZ1. Strain TZ1 effectively oxidized elemental sulfur to sulfate with an anode serving as the sole electron acceptor, at rates faster than Desulfobulbus propionicus, the only other organism in pure culture previously shown to oxidize S° with current production. The abundance of Desulfuromonas species enriched on the anodes of marine benthic fuel cells has previously been interpreted as acetate oxidation driving current production, but the results presented here suggest that sulfur-driven current production is a likely alternative.


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