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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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Profiles of dissolved oxygen within the A8 biofilm.
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pone-0073442-g008: Profiles of dissolved oxygen within the A8 biofilm.

Mentions: In the study, DO concentration was also determined using a microelectrode technique to get comprehensive understanding on how illumination affects the activity of algae at the micro-scale. Accompanying with the change in current, the DO rose to 18.3 mg L−1 under illumination, more than twice the saturated DO in deionized water (Figure 8), in agreement with Xiao et al. [30]. While in the dark, the DO concentration dropped to 4.22 mg L−1, lower than that of the control in light and suggesting that oxygen was consumed. Moreover, the DO concentration changed with the biofilm depth. In light, the DO apparently increased from 17.4 to 18.2 mg L−1 as the biofilm depth increased from −200 to 550 µm, and then decreased to 17.8 mg L−1 as the depth further increased to 800 µm. However, the DO within the biofilm decreased from 4.63 to 4.22 mg L−1 in the dark. For the control under illumination, the DO decreased from 8.75 to 8.52 mg L−1 as depth increased. These results demonstrated that A8 contributed to the DO concentration under illumination, which was dependent on the thickness of the biofilm. Under illumination, light energy was captured by chlorophyll antennae of algae, to split water with oxygen release [31]. Light intensity decreased as the biofilm depth increased, resulting in different amounts of energy captured by microalgae and thus different amounts of oxygen generated. The oxygen produced tended to diffuse out from the biofilm to the bulk solution. Therefore, the DO concentration first displayed an increasing gradient, but as the biofilm depth further increased, insufficient light for photosynthesis and oxygen consumption by microalgae/electrode resulted in the decreasing DO concentration.


Isolation, identification and characterization of an electrogenic microalgae strain.

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

Profiles of dissolved oxygen within the A8 biofilm.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0073442-g008: Profiles of dissolved oxygen within the A8 biofilm.
Mentions: In the study, DO concentration was also determined using a microelectrode technique to get comprehensive understanding on how illumination affects the activity of algae at the micro-scale. Accompanying with the change in current, the DO rose to 18.3 mg L−1 under illumination, more than twice the saturated DO in deionized water (Figure 8), in agreement with Xiao et al. [30]. While in the dark, the DO concentration dropped to 4.22 mg L−1, lower than that of the control in light and suggesting that oxygen was consumed. Moreover, the DO concentration changed with the biofilm depth. In light, the DO apparently increased from 17.4 to 18.2 mg L−1 as the biofilm depth increased from −200 to 550 µm, and then decreased to 17.8 mg L−1 as the depth further increased to 800 µm. However, the DO within the biofilm decreased from 4.63 to 4.22 mg L−1 in the dark. For the control under illumination, the DO decreased from 8.75 to 8.52 mg L−1 as depth increased. These results demonstrated that A8 contributed to the DO concentration under illumination, which was dependent on the thickness of the biofilm. Under illumination, light energy was captured by chlorophyll antennae of algae, to split water with oxygen release [31]. Light intensity decreased as the biofilm depth increased, resulting in different amounts of energy captured by microalgae and thus different amounts of oxygen generated. The oxygen produced tended to diffuse out from the biofilm to the bulk solution. Therefore, the DO concentration first displayed an increasing gradient, but as the biofilm depth further increased, insufficient light for photosynthesis and oxygen consumption by microalgae/electrode resulted in the decreasing DO concentration.

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