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Characterization of exoelectrogenic bacteria enterobacter strains isolated from a microbial fuel cell exposed to copper shock load.

Feng C, Li J, Qin D, Chen L, Zhao F, Chen S, Hu H, Yu CP - PLoS ONE (2014)

Bottom Line: Cyclic voltammetry measurements revealed that strain R2B1 had the capacity to transfer electrons to electrodes.The experimental results demonstrated that strain R2B1 was capable of utilizing a wide range of substrates, including Luria-Bertani (LB) broth, cellulose, acetate, citrate, glucose, sucrose, glycerol and lactose to generate electricity, with the highest current density of 440 mA·m-2 generated from LB-fed MFC.Further experiments indicated that the bacterial cell density had potential correlation with the current density.

View Article: PubMed Central - PubMed

Affiliation: Institute of Urban Environment, Chinese Academy of Sciences, Xiamen, 361021, China; Ningbo Urban Environment Observation and Research Station-NUEORS, Chinese Academy of Sciences, Ningbo, 351800, China.

ABSTRACT
Microorganisms capable of generating electricity in microbial fuel cells (MFCs) have gained increasing interest. Here fourteen exoelectrogenic bacterial strains were isolated from the anodic biofilm in an MFC before and after copper (Cu) shock load by Hungate roll-tube technique with solid ferric (III) oxide as an electron acceptor and acetate as an electron donor. Phylogenetic analysis of the 16S rRNA gene sequences revealed that they were all closely related to Enterobacter ludwigii DSM 16688T within the Enterobacteriaceae family, although these isolated bacteria showed slightly different morphology before and after Cu shock load. Two representative strains R2B1 (before Cu shock load) and B4B2 (after Cu shock load) were chosen for further analysis. B4B2 is resistant to 200 mg L-1 of Cu(II) while R2B1 is not, which indicated the potential selection of the Cu shock load. Raman analysis revealed that both R2B1 and B4B2 contained c-type cytochromes. Cyclic voltammetry measurements revealed that strain R2B1 had the capacity to transfer electrons to electrodes. The experimental results demonstrated that strain R2B1 was capable of utilizing a wide range of substrates, including Luria-Bertani (LB) broth, cellulose, acetate, citrate, glucose, sucrose, glycerol and lactose to generate electricity, with the highest current density of 440 mA·m-2 generated from LB-fed MFC. Further experiments indicated that the bacterial cell density had potential correlation with the current density.

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Phylogenic tree showing the relationships between isolated strains and closely related species based on 16S rRNA gene sequences.The sequence of Escherichia coli ATCC 25922 served as an outgroup sequence. 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. Scale bar  = 0.5% divergence.
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pone-0113379-g001: Phylogenic tree showing the relationships between isolated strains and closely related species based on 16S rRNA gene sequences.The sequence of Escherichia coli ATCC 25922 served as an outgroup sequence. 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. Scale bar  = 0.5% divergence.

Mentions: Fourteen 16S rRNA gene sequences (1386 bp) of isolated strains were obtained and subjected to comparative analysis with the 16S rRNA genes of closely related reference strains. According to the Figure 1, it is evident that these sequences obtained before and after Cu shock load formed distinct clusters in the neighbour-joining phylogenetic tree, referred to as Group I and Group II, respectively. Phylogenetic analysis revealed that both these two groups were within the family Geobacteraceae in the δ-Proteobacteria. The 16S rRNA gene sequences of isolated strains had the closest match to Enterobacter ludwigii DSM 16688T, ranging from 98.88% to 99.15%. Due to the high similarity among the strains obtained before (after) shock load, two representative strains R2B1 (before Cu shock load) and B4B2 (after Cu shock load) were chosen for further analysis. Strains R2B1 and B4B2 are gram-negative and the SEM and TEM images illustrated that they are 0.5–0.6 µm wide and 0.7–1.8 µm long rod, with a polar flagellum (Figure 2A, B, C, D). The cells occurred in aggregation, and had a few laterally inserted flagella and peritrichous cilium. The fact that these strains can grow both aerobically and anaerobically suggests that the strains are facultative anaerobes. These properties are similar to those of genus Enterobacter according to Bergey's Manual of Systematic Bacteriology. However, TEM images indicate that the pili of strain R2B1 are more than those of B4B2 (Figure 2C, D). In addition, when the isolated strains were cultivated on the LB agar plate, strain R2B1 showed a dramatically higher growth rate than that of strain B4B2 under the same cultivation condition.


Characterization of exoelectrogenic bacteria enterobacter strains isolated from a microbial fuel cell exposed to copper shock load.

Feng C, Li J, Qin D, Chen L, Zhao F, Chen S, Hu H, Yu CP - PLoS ONE (2014)

Phylogenic tree showing the relationships between isolated strains and closely related species based on 16S rRNA gene sequences.The sequence of Escherichia coli ATCC 25922 served as an outgroup sequence. 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. Scale bar  = 0.5% divergence.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4239067&req=5

pone-0113379-g001: Phylogenic tree showing the relationships between isolated strains and closely related species based on 16S rRNA gene sequences.The sequence of Escherichia coli ATCC 25922 served as an outgroup sequence. 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. Scale bar  = 0.5% divergence.
Mentions: Fourteen 16S rRNA gene sequences (1386 bp) of isolated strains were obtained and subjected to comparative analysis with the 16S rRNA genes of closely related reference strains. According to the Figure 1, it is evident that these sequences obtained before and after Cu shock load formed distinct clusters in the neighbour-joining phylogenetic tree, referred to as Group I and Group II, respectively. Phylogenetic analysis revealed that both these two groups were within the family Geobacteraceae in the δ-Proteobacteria. The 16S rRNA gene sequences of isolated strains had the closest match to Enterobacter ludwigii DSM 16688T, ranging from 98.88% to 99.15%. Due to the high similarity among the strains obtained before (after) shock load, two representative strains R2B1 (before Cu shock load) and B4B2 (after Cu shock load) were chosen for further analysis. Strains R2B1 and B4B2 are gram-negative and the SEM and TEM images illustrated that they are 0.5–0.6 µm wide and 0.7–1.8 µm long rod, with a polar flagellum (Figure 2A, B, C, D). The cells occurred in aggregation, and had a few laterally inserted flagella and peritrichous cilium. The fact that these strains can grow both aerobically and anaerobically suggests that the strains are facultative anaerobes. These properties are similar to those of genus Enterobacter according to Bergey's Manual of Systematic Bacteriology. However, TEM images indicate that the pili of strain R2B1 are more than those of B4B2 (Figure 2C, D). In addition, when the isolated strains were cultivated on the LB agar plate, strain R2B1 showed a dramatically higher growth rate than that of strain B4B2 under the same cultivation condition.

Bottom Line: Cyclic voltammetry measurements revealed that strain R2B1 had the capacity to transfer electrons to electrodes.The experimental results demonstrated that strain R2B1 was capable of utilizing a wide range of substrates, including Luria-Bertani (LB) broth, cellulose, acetate, citrate, glucose, sucrose, glycerol and lactose to generate electricity, with the highest current density of 440 mA·m-2 generated from LB-fed MFC.Further experiments indicated that the bacterial cell density had potential correlation with the current density.

View Article: PubMed Central - PubMed

Affiliation: Institute of Urban Environment, Chinese Academy of Sciences, Xiamen, 361021, China; Ningbo Urban Environment Observation and Research Station-NUEORS, Chinese Academy of Sciences, Ningbo, 351800, China.

ABSTRACT
Microorganisms capable of generating electricity in microbial fuel cells (MFCs) have gained increasing interest. Here fourteen exoelectrogenic bacterial strains were isolated from the anodic biofilm in an MFC before and after copper (Cu) shock load by Hungate roll-tube technique with solid ferric (III) oxide as an electron acceptor and acetate as an electron donor. Phylogenetic analysis of the 16S rRNA gene sequences revealed that they were all closely related to Enterobacter ludwigii DSM 16688T within the Enterobacteriaceae family, although these isolated bacteria showed slightly different morphology before and after Cu shock load. Two representative strains R2B1 (before Cu shock load) and B4B2 (after Cu shock load) were chosen for further analysis. B4B2 is resistant to 200 mg L-1 of Cu(II) while R2B1 is not, which indicated the potential selection of the Cu shock load. Raman analysis revealed that both R2B1 and B4B2 contained c-type cytochromes. Cyclic voltammetry measurements revealed that strain R2B1 had the capacity to transfer electrons to electrodes. The experimental results demonstrated that strain R2B1 was capable of utilizing a wide range of substrates, including Luria-Bertani (LB) broth, cellulose, acetate, citrate, glucose, sucrose, glycerol and lactose to generate electricity, with the highest current density of 440 mA·m-2 generated from LB-fed MFC. Further experiments indicated that the bacterial cell density had potential correlation with the current density.

Show MeSH
Related in: MedlinePlus