Type IV Pili-Independent Photocurrent Production by the Cyanobacterium Synechocystis sp. PCC 6803

thirumurthy, miyuki abirami; Hitchcock, Andrew; Cereda, Angelo; Liu, Jiawei; Chavez, Marko S.; Doss, Bryant L.; Ros, Robert; El‐Naggar, Mohamed Y.; Heap, John; Bibby, Thomas S.; Jones, Anne K.

doi:10.3389/fmicb.2020.01344

Cited by 40 publications

(32 citation statements)

References 75 publications

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“…a pattern of peaks and troughs before reaching a steady-state) that is not seen using isolated photosystem II (Fig. 1A), 8,[11][12][13][14][15][16] which is known to be the source of the electrons eventually exported during exoelectrogenesis. 17,18 We hypothesised that the complexity in the photocurrent profile results from the route taken by the electrons from photosystem II across the many outer layers of the cyanobacterial cell structure to the electrode (Fig.…”

Section: Introductionmentioning

confidence: 99%

“…23 There is some evidence of direct extracellular electron transfer via type IV pili, 24,25 but recent genetic and conductivity data call this into question. 15 There is evidence for an endogenous electron mediator (for example, a quinone or NADPH) that enables indirect extracellular electron transfer from the cell to the electrode surface. 13,26,27 The mechanism of electron transfer by isolated proteins, including photosystem II, has been well studied using electrochemistry.…”

Section: Introductionmentioning

confidence: 99%

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A biophotoelectrochemical approach to unravelling the role of cyanobacterial cell structures in exoelectrogenesis

Wey

Lawrence

Chen

et al. 2021

Preprint

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Photosynthetic microorganisms can export electrons outside their cells, a phenomenon called exoelectrogenesis, which can be harnessed for solar energy conversion. However, the route electrons take from thylakoid membranes to the cell exterior is not understood. Electrochemistry is a powerful analytical technique for studying electron transfer pathways. Here, we show how photoelectrochemistry can be used to compare electron flux from cyanobacterial cells of different growth stages, species and with the outer layers systematically removed. We show that the periplasmic space contributes significantly to the photocurrent profile complexity of whole cells, indicating that it gates electron transfer in exoelectrogenesis. We found that although components of the type IV pili machinery do not have a role in exoelectrogenesis, they contribute significantly to cell-electrode adherence. This study establishes that analytical photoelectrochemistry and molecular microbiology provide a powerful combination to study exoelectrogenesis, enabling future studies to answer biological questions and advance solar energy conversion applications.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A biophotoelectrochemical approach to unravelling the role of cyanobacterial cell structures in exoelectrogenesis

Wey

Lawrence

Chen

et al. 2021

Preprint

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“…Some of the mediators are toxic and most have a low solubility in water-based media ( Cereda, 2014 ). The use of exogenous mediators might be avoided using a semi-dry cyanobacterial monolayer which can produce current by a DET mechanism ( Sekar et al., 2016 ; Thirumurthy et al., 2020 ; Wei et al., 2016 ); however, such systems might damage the survival of the cyanobacteria and limit its ability to multiply which might be very important for construction of useful systems. One of the possible mechanisms for DET with cyanobacteria is through type IV pili.…”

Section: Introductionmentioning

confidence: 99%

NADPH performs mediated electron transfer in cyanobacterial-driven bio-photoelectrochemical cells

et al. 2021

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Summary Previous studies have shown that live cyanobacteria can produce photocurrent in bio-photoelectrochemical cells (BPECs) that can be exploited for clean renewable energy production. Electron transfer from cyanobacteria to the electrochemical cell was proposed to be facilitated by small molecule(s) mediator(s) whose identity (or identities) remain unknown. Here, we elucidate the mechanism of electron transfer in the BPEC by identifying the major electron mediator as NADPH in three cyanobacterial species. We show that an increase in the concentration of NADPH secreted into the external cell medium (ECM) is obtained by both illumination and activation of the BPEC. Elimination of NADPH in the ECM abrogates the photocurrent while addition of exogenous NADP + significantly increases and prolongs the photocurrent production. NADP + is thus the first non-toxic, water soluble electron mediator that can functionally link photosynthetic cells to an energy conversion system and may serve to improve the performance of future BPECs.

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“…However, these redox-active proteins have not yet been identified in S6803. It has been suggested that ARTO and/or Type IV pili are involved in the iron uptake process in S6803 ( Kranzler et al, 2014 ; Lamb et al, 2014 ), and such factors may also contribute to ferrihydrite reduction and electricity generation by this microbe ( Figure 1 ) [of note, a recent paper reported that pili has little impact on the photo-current generation capability ( Thirumurthy et al, 2020 )]. Another possibility is that a diffusive electron mediator excreted from the cells was responsible for ferrihydrite reduction.…”

Section: Discussionmentioning

confidence: 99%

Ferrihydrite Reduction by Photosynthetic Synechocystis sp. PCC 6803 and Its Correlation With Electricity Generation

et al. 2021

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Microbial extracellular electron transfer (EET) to solid-state electron acceptors such as anodes and metal oxides, which was originally identified in dissimilatory metal-reducing bacteria, is a key process in microbial electricity generation and the biogeochemical cycling of metals. Although it is now known that photosynthetic microorganisms can also generate (photo)currents via EET, which has attracted much interest in the field of biophotovoltaics, little is known about the reduction of metal (hydr)oxides via photosynthetic microbial EET. The present work quantitatively assessed the reduction of ferrihydrite in conjunction with the EET of the photosynthetic microbe Synechocystis sp. PCC 6803. Microbial reduction of ferrihydrite was found to be initiated in response to light but proceeded at higher rates when exogenous glucose was added, even under dark conditions. These results indicate that current generation from Synechocystis cells does not always need light irradiation. The qualitative trends exhibited by the ferrihydrite reduction rates under various conditions showed significant correlation with those of the microbial currents. Notably, the maximum concentration of Fe(II) generated by the cyanobacterial cells under dark conditions in the presence of glucose was comparable to the levels observed in the photic layers of Fe-rich microbial mats.

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Type IV Pili-Independent Photocurrent Production by the Cyanobacterium Synechocystis sp. PCC 6803

Cited by 40 publications

References 75 publications

A biophotoelectrochemical approach to unravelling the role of cyanobacterial cell structures in exoelectrogenesis

A biophotoelectrochemical approach to unravelling the role of cyanobacterial cell structures in exoelectrogenesis

NADPH performs mediated electron transfer in cyanobacterial-driven bio-photoelectrochemical cells

Ferrihydrite Reduction by Photosynthetic Synechocystis sp. PCC 6803 and Its Correlation With Electricity Generation

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