Bioelectrocatalytic sulfide oxidation by a haloalkaliphilic electroactive microbial community dominated by Desulfobulbaceae

Singh, Ramandeep; Chaudhary, Srishti; Yadav, Ravi Kumar; Patil, Sunil A.

doi:10.1016/j.electacta.2022.140576

Cited by 11 publications

(6 citation statements)

References 39 publications

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“…The electrochemical cultivation approach was used to grow the G. halelectricus biofilm at the anode surface, which served as the sole terminal electron acceptor (Singh et al, 2022). For this, potentiostatically controlled two-chambered reactors with a three-electrode configuration were used.…”

Section: Electrochemical Setup and Microbial Biofilm Growth At The El...mentioning

confidence: 99%

“…Graphite plates with a projected surface area of 7.0125 cm 2 were used as anode and cathode electrodes. The membrane and graphite electrodes were pre-treated before use according to protocols mentioned elsewhere (Singh et al, 2022). An Ag/AgCl (3.5 M KCl, 0.205 V vs. SHE, RE-1B, Biologic Science Instruments, France) reference electrode was placed in the anode chamber to monitor the electrode potentials.…”

Section: Electrochemical Setup and Microbial Biofilm Growth At The El...mentioning

confidence: 99%

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The bidirectional extracellular electron transfer process aids iron cycling by Geoalkalibacter halelectricus in a highly saline-alkaline condition

Yadav,

Sadhotra,

Patil

2023

Appl Environ Microbiol

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Bidirectional extracellular electron transfer (EET) is crucial to upholding microbial metabolism with insoluble electron acceptors or donors in anoxic environments. Investigating bidirectional EET-capable microorganisms is desired to understand the cell-cell and microbe-mineral interactions and their role in mineral cycling besides leveraging their energy generation and conversion, biosensing, and bio-battery applications. Here, we report on iron cycling by haloalkaliphilic Geoalkalibacter halelectricus via bidirectional EET under haloalkaline conditions. It efficiently reduces Fe 3+ oxide (Fe 2 O 3 ) to Fe 0 at a 0.75 ± 0.08 mM/mg protein /d rate linked to acetate oxidation via outward EET and oxidizes Fe 0 to Fe 3+ at a 0.24 ± 0.03 mM/mg protein /d rate via inward EET to reduce fumarate. Bioelectrochemical cultivation confirmed its outward and inward EET capabilities. It produced 895 ± 23 µA/cm 2 current by linking acetate oxidation to anode reduction via outward EET and reduced fumarate by drawing electrons from the cathode (‒2.5 ± 0.3 µA/cm 2 ) via inward EET. The cyclic voltammograms of G. halelectricu s biofilms revealed redox moieties with different formal potentials, suggesting the involvement of different membrane components in bidirectional EET. The cyclic voltammetry and GC-MS analysis of the cell-free spent medium revealed the lack of soluble redox mediators, suggesting direct electron transfer by G. halelecctricu s in achieving bidirectional EET. By reporting on the first haloalkaliphilic bacterium capable of oxidizing and reducing insoluble Fe 0 and Fe 3+ oxide, respectively, this study advances the limited understanding of the metabolic capabilities of extremophiles to respire on insoluble electron acceptors or donors via bidirectional EET and invokes the possible role of G. halelectricu s in iron cycling in barely studied haloalkaline environments. IMPORTANCE Bidirectional extracellular electron transfer (EET) appears to be a key microbial metabolic process in anoxic environments that are depleted in soluble electron donor and acceptor molecules. Though it is an ecologically important and applied microbial phenomenon, it has been reported with a few microorganisms, mostly from nonextreme environments. Moreover, direct electron transfer-based bidirectional EET is studied for very few microorganisms with electrodes in engineered systems and barely with the natural insoluble electron acceptor and donor molecules in anoxic conditions. This study advances the understanding of extremophilic microbial taxa capable of bidirectional EET and its role in barely investigated Fe cycling in highly saline-alkaline environments. It also offers research opportunities for understanding the membrane components involved in the bidirectional EET of G. halelectricus . The high rate of Fe 3+ oxide reduction activity by G. halelectricus suggests its possible use as a biocatalyst in the anaerobic iron bioleaching process under neutral-alkaline pH conditions.

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Section: Electrochemical Setup and Microbial Biofilm Growth At The El...mentioning

confidence: 99%

Section: Electrochemical Setup and Microbial Biofilm Growth At The El...mentioning

confidence: 99%

The bidirectional extracellular electron transfer process aids iron cycling by Geoalkalibacter halelectricus in a highly saline-alkaline condition

Yadav,

Sadhotra,

Patil

2023

Appl Environ Microbiol

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“…To check the capabilities to respire both soluble and insoluble electron acceptors via EET, the isolated strain was anaerobically cultivated on a modified M9 medium supplemented with soluble (fumarate and sulfate [SO 4 2− ]) and insoluble (mineral oxides, namely, ferric oxide [Fe 2 O 3 ] and manganese oxide [MnO 4 ]), as the sole electron acceptors. For sulfate experiments, both reactant (sulfate [SO 4 2− ]) and reduced product (sulfide [S 2− ]) were analysed using turbidimetric and methylene blue methods, respectively with a UV–Vis spectrophotometer (WTW PhotoLab® 7600) (Rice et al, 2012; Singh et al, 2022a, 2022b). Acetate served as the sole source of carbon and electrons in all but different substrate utilization tests.…”

Section: Methodsmentioning

confidence: 99%

“…Mn 4+ 2À ]) and reduced product (sulfide [S 2À ]) were analysed using turbidimetric and methylene blue methods, respectively with a UV-Vis spectrophotometer (WTW PhotoLab ® 7600) (Rice et al, 2012;Singh et al, 2022aSingh et al, , 2022b. Acetate served as the sole source of carbon and electrons in all but different substrate utilization tests.…”

Section: Biochemical Characterizationmentioning

confidence: 99%

“…The EET capabilities, that is, electroactivity of SAP-1 was tested by checking its capability to respire on a solid-state electron acceptor, that is, electrode via the electrochemical cultivation approach (Chiranjeevi & Patil, 2020;Singh et al, 2022aSingh et al, , 2022b. On inoculation of the triplicate bioelectrochemical reactors with SAP-1 culture, the bioelectrocatalytic current response associated with the acetate oxidation linked to the electrode reduction process was observed.…”

Section: Eet Capability Testing and Characterization Of The Novel Strainmentioning

confidence: 99%

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Geoalkalibacter halelectricus SAP‐1 sp. nov. possessing extracellular electron transfer and mineral‐reducing capabilities from a haloalkaline environment

Yadav

Singh

Sundharam

et al. 2022

Environmental Microbiology

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The extracellular electron transfer (EET)-capable electroactive microorganisms (EAMs) play crucial roles in mineral cycling and interspecies electron transfer in different environments and are used as biocatalysts in microbial electrochemical technologies. Studying EAMs from extreme environments is desired to advance the electromicrobiology discipline, understanding their unique metabolic traits with implications to extreme microbiology, and develop specific bioelectrochemical applications. Here, we present a novel haloalkaliphilic bacterium named Geoalkalibacter halelectricus SAP-1, isolated from a microbial electroactive biofilm enriched from the haloalkaline lake sediments. It is a rod-shaped Gram-negative heterotrophic anaerobe that uses various carbon and energy sources and respires on soluble and insoluble terminal electron acceptors. Besides 16S-rRNA and wholegenome sequence-based phylogeny, the GGDC values of 21.7%, ANI of 78.5%, and 2.77% genomic DNA GC content difference with the closest validly named species Geoalkalibacter ferrihydriticus (DSM 17813 T ) confirmed its novelty. When grown with the solid-state electrode as the only electron acceptor, it produced 460 AE 23 μA/cm 2 bioelectrocatalytic current, thereby confirming its electroactivity. Further electrochemical analysis revealed the presence of membrane redox components with a high formal potential, putatively involved in the direct mode of EET. These are distinct from EET components reported for any known electroactive microorganisms, including well-studied Geobacter spp., Shewanella spp., and Desulfuromonas acetexigens. The capabilities of G. halelectricus SAP-1 to respire on soluble and insoluble electron acceptors including fumarate, SO 4 2À , Fe 3+ , and Mn 4+ suggests its role in cycling these elements in haloalkaline environments.

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Electroactive (Micro)organisms

Noordam,

Madjarov,

Louro

et al. 2024

Geomicrobiology: Natural and Anthropogenic Settings

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Bioelectrocatalytic sulfide oxidation by a haloalkaliphilic electroactive microbial community dominated by Desulfobulbaceae

Cited by 11 publications

References 39 publications

The bidirectional extracellular electron transfer process aids iron cycling by Geoalkalibacter halelectricus in a highly saline-alkaline condition

The bidirectional extracellular electron transfer process aids iron cycling by Geoalkalibacter halelectricus in a highly saline-alkaline condition

Geoalkalibacter halelectricus SAP‐1 sp. nov. possessing extracellular electron transfer and mineral‐reducing capabilities from a haloalkaline environment

Electroactive (Micro)organisms

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