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Isolation, identification and characterization of an electrogenic microalgae strain.

Wu Y, Guan K, Wang Z, Xu B, Zhao F - PLoS ONE (2013)

Bottom Line: One species showed direct electron transfer via membrane-associated proteins and indirect electron transfer via secreted oxygen.Dissolved oxygen concentration measurement showed gradients within the microalgae biofilm: 18.3 mg L(-1) in light decreasing to 4.29 mg L(-1) in the dark.This study diversified the exoelectrogen library and provided a potential model microalga to explore the associated mechanism of extracellular electron transfer.

View Article: PubMed Central - PubMed

Affiliation: Institute of Urban Environment, Chinese Academy of Sciences, Xiamen, People's Republic of China.

ABSTRACT
Extracellular electron transfer involving microbes is important as it closely reflects the ability of cells to communicate with the environment. However, there are few reports on electron transfer mechanisms of pure microalgae and a lack of any model alga to study the transfer processes. In the present study, nine green microalgae species were isolated from wastewater and characterized in terms of their ability to transfer electrons between cells and an electrode. One species showed direct electron transfer via membrane-associated proteins and indirect electron transfer via secreted oxygen. The microalga was identified as Desmodesmus sp. based on phylogenetic analysis and electron microscopy. Electrochemical tests demonstrated that Desmodesmus sp. was able to act as a cathodic microorganism. Stable current densities of -0.24, 35.54 and 170 mA m(-2) were achieved at potentials of +0.2, -0.2 and -0.4 V, respectively, under illumination. Dissolved oxygen concentration measurement showed gradients within the microalgae biofilm: 18.3 mg L(-1) in light decreasing to 4.29 mg L(-1) in the dark. This study diversified the exoelectrogen library and provided a potential model microalga to explore the associated mechanism of extracellular electron transfer.

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Related in: MedlinePlus

Cyclic voltammograms of strain A8 on glassy carbon under anaerobic conditions.
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pone-0073442-g002: Cyclic voltammograms of strain A8 on glassy carbon under anaerobic conditions.

Mentions: To evaluate the redox activity of the nine isolates, CV measurements for the isolated microalgae on glassy carbon were carried out under anaerobic conditions. The supernatant of the microalgae culture solutions were also collected at the end of the batch experiment. As shown in Figure 2, an oxidation peak was observed in the potential range of +100 to +200 mV for the isolated alga A8 under nitrogen conditions, but no peaks were observed when the supernatant was tested (Figure S1 in File S1). The ability of electron transfer at electrode/biofilm interfaces is the characteristic to distinguish exoelectrogens. For bacteria (i.e. Shewanella oneidensis MR-1 [20] and Geobacter sulferreducens[21]), mechanisms including indirect transfer via flavin and direct transfer via proteins were reported [19]; some cytochromes of terminal reductases are involved in electron transfer processes. For microalga A8, since there was no electrochemical response of the supernatant, a proposed mechanism is that some proteins such as cytochromes on the outer membrane may be involved in direct electron transfer involving A8. After electrochemical testing, the A8 strain was adopted for further study.


Isolation, identification and characterization of an electrogenic microalgae strain.

Wu Y, Guan K, Wang Z, Xu B, Zhao F - PLoS ONE (2013)

Cyclic voltammograms of strain A8 on glassy carbon under anaerobic conditions.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3760914&req=5

pone-0073442-g002: Cyclic voltammograms of strain A8 on glassy carbon under anaerobic conditions.
Mentions: To evaluate the redox activity of the nine isolates, CV measurements for the isolated microalgae on glassy carbon were carried out under anaerobic conditions. The supernatant of the microalgae culture solutions were also collected at the end of the batch experiment. As shown in Figure 2, an oxidation peak was observed in the potential range of +100 to +200 mV for the isolated alga A8 under nitrogen conditions, but no peaks were observed when the supernatant was tested (Figure S1 in File S1). The ability of electron transfer at electrode/biofilm interfaces is the characteristic to distinguish exoelectrogens. For bacteria (i.e. Shewanella oneidensis MR-1 [20] and Geobacter sulferreducens[21]), mechanisms including indirect transfer via flavin and direct transfer via proteins were reported [19]; some cytochromes of terminal reductases are involved in electron transfer processes. For microalga A8, since there was no electrochemical response of the supernatant, a proposed mechanism is that some proteins such as cytochromes on the outer membrane may be involved in direct electron transfer involving A8. After electrochemical testing, the A8 strain was adopted for further study.

Bottom Line: One species showed direct electron transfer via membrane-associated proteins and indirect electron transfer via secreted oxygen.Dissolved oxygen concentration measurement showed gradients within the microalgae biofilm: 18.3 mg L(-1) in light decreasing to 4.29 mg L(-1) in the dark.This study diversified the exoelectrogen library and provided a potential model microalga to explore the associated mechanism of extracellular electron transfer.

View Article: PubMed Central - PubMed

Affiliation: Institute of Urban Environment, Chinese Academy of Sciences, Xiamen, People's Republic of China.

ABSTRACT
Extracellular electron transfer involving microbes is important as it closely reflects the ability of cells to communicate with the environment. However, there are few reports on electron transfer mechanisms of pure microalgae and a lack of any model alga to study the transfer processes. In the present study, nine green microalgae species were isolated from wastewater and characterized in terms of their ability to transfer electrons between cells and an electrode. One species showed direct electron transfer via membrane-associated proteins and indirect electron transfer via secreted oxygen. The microalga was identified as Desmodesmus sp. based on phylogenetic analysis and electron microscopy. Electrochemical tests demonstrated that Desmodesmus sp. was able to act as a cathodic microorganism. Stable current densities of -0.24, 35.54 and 170 mA m(-2) were achieved at potentials of +0.2, -0.2 and -0.4 V, respectively, under illumination. Dissolved oxygen concentration measurement showed gradients within the microalgae biofilm: 18.3 mg L(-1) in light decreasing to 4.29 mg L(-1) in the dark. This study diversified the exoelectrogen library and provided a potential model microalga to explore the associated mechanism of extracellular electron transfer.

Show MeSH
Related in: MedlinePlus