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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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Phylogenetic tree of strain A8 and closely related species based on ITS sequences of ribosomal DNA.The tree was constructed using the neighbor-joining method. The numbers at nodes indicate the percentages of occurrence of the branching order in 1000 bootstrapped trees for values greater than 50%. Scale bar = 1% divergence.
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pone-0073442-g005: Phylogenetic tree of strain A8 and closely related species based on ITS sequences of ribosomal DNA.The tree was constructed using the neighbor-joining method. The numbers at nodes indicate the percentages of occurrence of the branching order in 1000 bootstrapped trees for values greater than 50%. Scale bar = 1% divergence.

Mentions: The ITS1 and ITS2 sequences are important alternative markers for investigating the phylogenetic relationship within the Scenedesmaceae[26]. To assess the molecular diversity of the morphotype represented by strain A8, the 18S rRNA gene–ITS1–5.8S rRNA gene–ITS2 regions were sequenced. The length of the sequence amplied was 714 bp, including 27 bp 18S rRNA gene, 213 bp ITS1, 181 bp 5.8S rRNA gene, 280 bp ITS2, and 13 bp 28S rRNA gene. The sequence in this study has been deposited in the GenBank database under accession number JQ973888. BLAST was applied to find regions of similarity between biological sequences. The results showed that strain A8 should indeed be assigned to the genus Desmodesmus and was most closely related to Desmodesmus hystrix isolate NDem 9/21 T-9W DQ417551 (98% sequence similarity), Desmodesmus brasiliensis FR865708 (96% sequence similarity), and Desmodesmus pannonicus FR865710 (94% sequence similarity). These three strains formed a distinct subcluster in the neighbor-joining, in which the new isolate and Desmodesmus hystrix isolate NDem 9/21 T-9W DQ417551 formed a distinct subline (Figure 5).


Isolation, identification and characterization of an electrogenic microalgae strain.

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

Phylogenetic tree of strain A8 and closely related species based on ITS sequences of ribosomal DNA.The tree was constructed using the neighbor-joining method. The numbers at nodes indicate the percentages of occurrence of the branching order in 1000 bootstrapped trees for values greater than 50%. Scale bar = 1% divergence.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0073442-g005: Phylogenetic tree of strain A8 and closely related species based on ITS sequences of ribosomal DNA.The tree was constructed using the neighbor-joining method. The numbers at nodes indicate the percentages of occurrence of the branching order in 1000 bootstrapped trees for values greater than 50%. Scale bar = 1% divergence.
Mentions: The ITS1 and ITS2 sequences are important alternative markers for investigating the phylogenetic relationship within the Scenedesmaceae[26]. To assess the molecular diversity of the morphotype represented by strain A8, the 18S rRNA gene–ITS1–5.8S rRNA gene–ITS2 regions were sequenced. The length of the sequence amplied was 714 bp, including 27 bp 18S rRNA gene, 213 bp ITS1, 181 bp 5.8S rRNA gene, 280 bp ITS2, and 13 bp 28S rRNA gene. The sequence in this study has been deposited in the GenBank database under accession number JQ973888. BLAST was applied to find regions of similarity between biological sequences. The results showed that strain A8 should indeed be assigned to the genus Desmodesmus and was most closely related to Desmodesmus hystrix isolate NDem 9/21 T-9W DQ417551 (98% sequence similarity), Desmodesmus brasiliensis FR865708 (96% sequence similarity), and Desmodesmus pannonicus FR865710 (94% sequence similarity). These three strains formed a distinct subcluster in the neighbor-joining, in which the new isolate and Desmodesmus hystrix isolate NDem 9/21 T-9W DQ417551 formed a distinct subline (Figure 5).

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