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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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Light microscope (1000×) pictures of microalgae isolates.
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pone-0073442-g001: Light microscope (1000×) pictures of microalgae isolates.

Mentions: Wastewater was sampled onto agar plates. Green microalgae clones were picked up after a few cycles of agar plate spreading. Nine species were isolated. The morphology of isolated strains was observed with light microscopy (Figure 1). Five species (Figure 1b,1 e,1 f, 1h and 1i) were spheres with different size, of which the largest diameter is about 30 µm (Figure 1b) and the smallest one is about 3 µm (Figure 1i). The isolated unicellular alga shown in Figure 1a has a spherical cell body with spiny projections, and a diameter of 18–20 µm, which are the diagnostic characteristics of Golenkinia. From Figure 1d, the cells are deeply divided in the middle by a short isthmus, and the two semi-cells are oval. Microscopic analysis of the samples allowed preliminary identification of this isolate as genus Cosmarium. Two Desmodesmus with different size and form were isolated (Figure 1c and 1g); one is a four-cell coenobia which is crescent-shaped, and the other is two-cell coenobia which is the most frequently with oven form and denoted A8.


Isolation, identification and characterization of an electrogenic microalgae strain.

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

Light microscope (1000×) pictures of microalgae isolates.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0073442-g001: Light microscope (1000×) pictures of microalgae isolates.
Mentions: Wastewater was sampled onto agar plates. Green microalgae clones were picked up after a few cycles of agar plate spreading. Nine species were isolated. The morphology of isolated strains was observed with light microscopy (Figure 1). Five species (Figure 1b,1 e,1 f, 1h and 1i) were spheres with different size, of which the largest diameter is about 30 µm (Figure 1b) and the smallest one is about 3 µm (Figure 1i). The isolated unicellular alga shown in Figure 1a has a spherical cell body with spiny projections, and a diameter of 18–20 µm, which are the diagnostic characteristics of Golenkinia. From Figure 1d, the cells are deeply divided in the middle by a short isthmus, and the two semi-cells are oval. Microscopic analysis of the samples allowed preliminary identification of this isolate as genus Cosmarium. Two Desmodesmus with different size and form were isolated (Figure 1c and 1g); one is a four-cell coenobia which is crescent-shaped, and the other is two-cell coenobia which is the most frequently with oven form and denoted A8.

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