15 research outputs found
In Situ Investigation of Cathode and Local Biofilm Microenvironments Reveals Important Roles of OH<sup>ā</sup> and Oxygen Transport in Microbial Fuel Cells
Mass
transport within a cathode, including OH<sup>ā</sup> transport
and oxygen diffusion, is important for the performance
of air-cathode microbial fuel cells (MFCs). However, little is known
regarding how mass transport profiles are associated with MFC performance
and how they are affected by biofilm that inevitably forms on the
cathode surface. In this study, the OH<sup>ā</sup> and oxygen
profiles of a cathode biofilm were probed in situ in an MFC using
microelectrodes. The pH of the catalyst layer interface increased
from 7.0 Ā± 0.1 to 9.4 Ā± 0.3 in a buffered MFC with a bare
cathode, which demonstrates significant accumulation of OH<sup>ā</sup> in the cathode region. Furthermore, the pH of the interface increased
to 10.0 Ā± 0.3 in the presence of the local biofilm, which indicates
that OH<sup>ā</sup> transport was severely blocked. As a result
of the significant OH<sup>ā</sup> accumulation, the maximum
power density of the MFC decreased from 1.8 Ā± 0.1 W/m<sup>2</sup> to 1.5 Ā± 0.08 W/m<sup>2</sup>. In contrast, oxygen crossover,
which was significant under low current flow conditions, was limited
by the cathode biofilm. As a result of the blocked oxygen crossover,
higher MFC coulombic efficiency (CE) was achieved in the presence
of the cathode biofilm. These results indicate that enhanced OH<sup>ā</sup> transport and decreased oxygen crossover would be
beneficial for high-performance MFC development
Disposable Strip Biosensor for Visual Detection of Hg<sup>2+</sup> Based on Hg<sup>2+</sup>-Triggered Toehold Binding and Exonuclease III-Assisted Signal Amplification
A disposable
strip biosensor for the visual detection of Hg<sup>2+</sup> in aqueous
solution has been constructed on the basis of
Hg<sup>2+</sup>-triggered toehold binding and exonuclease III (Exo
III)-assisted signal amplification. Thymine-thymine (T-T) mismatches
in the toehold domains can serve as specific recognition elements
for Hg<sup>2+</sup> binding with the help of T-Hg<sup>2+</sup>-T base
pairs to initiate toehold-mediated strand displacement reaction. Exo
III-catalyzed target recycling strategy is introduced to improve the
sensitivity. Using gold nanoparticles as a tracer, the output signals
can be directly observed by the naked eye. The assay is ultrasensitive,
enabling the visual detection of trace amounts of Hg<sup>2+</sup> as
low as 1 pM without instrumentation. This sensing system also displays
remarkable specificity to Hg<sup>2+</sup> against other possible competing
ions. This sensor is robust and can be applied to the reliable monitoring
of spiked Hg<sup>2+</sup> in environmental water samples with good
recovery and accuracy. With the advantages of cost-effectiveness,
simplicity, portability, and convenience, the disposable strip biosensor
will be a promising candidate for point-of-use monitoring of Hg<sup>2+</sup> in environmental and biological samples
Additional file 1: Table S1. of Genome sequence of a dissimilatory Fe(III)-reducing bacterium Geobacter soli type strain GSS01T
Associated MIGS record. (PDF 191 kb
Additional file 2: of Genome sequence of a dissimilatory Fe(III)-reducing bacterium Geobacter soli type strain GSS01T
Amino acid sequence alignment of pilin domain protein SE37_07695 from Geobacter soli GSS01 and those from other bacteria. Amino acid sequence alignments were generated using the Clustal X (1.8). (PDF 40 kb
Nanostructured Macroporous Bioanode Based on Polyaniline-Modified Natural Loofah Sponge for High-Performance Microbial Fuel Cells
Microbial fuel cells (MFCs) are a
promising technology to recover
electrical energy from different types of waste. However, the power
density of MFCs for practical applications is limited by the anode
performance, mainly resulting from low bacterial loading capacity
and low extracellular electron transfer (EET) efficiency. In this
study, an open three-dimensional (3D) structured electrode was fabricated
using a natural loofah sponge as the precursor material. The loofah
sponge was directly converted into a continuous 3D macroporous carbon
material via a simple carbonization procedure. The loofah sponge carbon
(LSC) was decorated with nitrogen-enriched carbon nanoparticles by
cocarbonizing polyaniline-hybridized loofah sponges to improve their
microscopic structures. The macroscale porous structure of the LSCs
greatly increased the bacterial loading capacity. The microscale coating
of carbon nanoparticles favored EET due to the enhanced interaction
between the bacteria and the anode. By using a single-chamber MFC
equipped with the fabricated anode, a power density of 1090 Ā±
72 mW m<sup>ā2</sup> was achieved, which is much greater than
that obtained by similarly sized traditional 3D anodes. This study
introduces a promising method for the fabrication of high-performance
anodes from low-cost, sustainable natural materials
Rapid Measurement of Microbial Extracellular Respiration Ability Using a High-Throughput Colorimetric Assay
Microbial extracellular respiration
(MER) involves the transfer
of electrons to extracellular substrates and has significant environmental
implications. Conventional methods for MER ability determination are
reagent- and time-consuming, have a low throughput, or require noncommercial
instruments. In this study, a plate-based colorimetric assay is proposed
to measure MER ability. This method utilizes the peroxidase activity
of the key components (multi-heme <i>c</i>-type cytochromes)
of the extracellular electron-transfer network. The bacterial intrinsic
peroxidase-catalyzed oxidation of chromogen (e.g., tetramethylbenzidine)
resulted in a measurable color change correlated with the MER ability
of the tested microorganisms. The results of the proposed colorimetric
assay correspond well with those of traditional methods, such as the
dissimilatory FeĀ(III) reduction method (Spearmanās Ļ
of 0.946; <i>P</i> < 0.01) and the electricity generation
method (Spearmanās Ļ of 0.893; <i>P</i> <
0.01). The proposed method allows researchers to identify extracellular
respiring bacteria within several minutes and to measure their MER
ability quantitatively by a plate-based assay
TiO<sub>2</sub> Nanoparticle-Induced Nanowire Formation Facilitates Extracellular Electron Transfer
Semiconductor nanoparticles (NPs)
have been reported to facilitate
extracellular electron transfer (EET) by increasing the electrical
conductivity of electroactive biofilms. However, the underlying molecular
mechanisms remain unclear. In this study, we demonstrated the unique
role of semiconductor titanium dioxide (TiO<sub>2</sub>) NPs in facilitating
EET from <i>Geobacter</i> cells to an electrode. Compared
to other NPs that include conductor carbon, semiconductor Ī±-Fe<sub>2</sub>O<sub>3</sub>, and insulator SiO<sub>2</sub>, TiO<sub>2</sub> NPs improved the bacterial EET capability most significantly, leading
to an approximately 5.1-fold increase in microbial current generation.
Cell morphology and gene analysis revealed that TiO<sub>2</sub> NPs
specifically induced the formation of conductive nanowires by stimulating <i>pilA</i> expression, which primarily contributed to the enhanced
EET in biofilms. In addition, TiO<sub>2</sub> NPs might compensate
for the lack of a pili-associated <i>c</i>-cytochrome OmcS
in the EET function. This finding had important implications not only
for optimizing the performance of electroactive biofilms but also
for modulating the ecological impact of NPs in the natural environment
Table_3_Transcriptomic, Proteomic, and Bioelectrochemical Characterization of an Exoelectrogen Geobacter soli Grown With Different Electron Acceptors.pdf
<p>The ability of Geobacter species to transfer electrons outside cells enables them to play an important role in biogeochemical and bioenergy processes. Our knowledge of the extracellular electron transfer (EET) process in the genus Geobacter is mainly from the study of G. sulfurreducens, and in order to fully investigate the EET mechanisms in the genus Geobacter, other Geobacter species should also be considered. This study focused on the EET of Geobacter soli GSS01, which exhibited a capability of reducing insoluble Fe(III) oxides and generating electrical current comparable with G. sulfurreducens PCA. Electrochemical characterization, including cyclic voltammetry, differential pulse voltammetry, and electrochemical in situ FTIR spectra, revealed that different redox proteins contributed to the electrochemical behaviors of G. soli and G. sulfurreducens. Based on comparative transcriptomic and proteomic analyses, OmcS was the most upregulated protein in both G. soli and G. sulfurreducens cells grown with insoluble Fe(III) oxides vs. soluble electron acceptor. However, the proteins including OmcE and PilA that were previously reported as being important for EET in G. sulfurreducens were downregulated or unchanged in G. soli cells grown with insoluble electron acceptors vs. soluble electron acceptor, and many proteins that were upregulated in G. soli cells grown with insoluble electron acceptors vs. soluble electron acceptor, such as OmcN, are not important for EET in G. sulfurreducens. We also identified 30 differentially expressed small RNAs (sRNAs) in G. soli cells grown with different acceptors. Taken together, these findings help to understand the versatile EET mechanisms that exist in the genus Geobacter and point to the possibility of sRNA in modulating EET gene expression.</p
Table_1_Transcriptomic, Proteomic, and Bioelectrochemical Characterization of an Exoelectrogen Geobacter soli Grown With Different Electron Acceptors.xlsx
<p>The ability of Geobacter species to transfer electrons outside cells enables them to play an important role in biogeochemical and bioenergy processes. Our knowledge of the extracellular electron transfer (EET) process in the genus Geobacter is mainly from the study of G. sulfurreducens, and in order to fully investigate the EET mechanisms in the genus Geobacter, other Geobacter species should also be considered. This study focused on the EET of Geobacter soli GSS01, which exhibited a capability of reducing insoluble Fe(III) oxides and generating electrical current comparable with G. sulfurreducens PCA. Electrochemical characterization, including cyclic voltammetry, differential pulse voltammetry, and electrochemical in situ FTIR spectra, revealed that different redox proteins contributed to the electrochemical behaviors of G. soli and G. sulfurreducens. Based on comparative transcriptomic and proteomic analyses, OmcS was the most upregulated protein in both G. soli and G. sulfurreducens cells grown with insoluble Fe(III) oxides vs. soluble electron acceptor. However, the proteins including OmcE and PilA that were previously reported as being important for EET in G. sulfurreducens were downregulated or unchanged in G. soli cells grown with insoluble electron acceptors vs. soluble electron acceptor, and many proteins that were upregulated in G. soli cells grown with insoluble electron acceptors vs. soluble electron acceptor, such as OmcN, are not important for EET in G. sulfurreducens. We also identified 30 differentially expressed small RNAs (sRNAs) in G. soli cells grown with different acceptors. Taken together, these findings help to understand the versatile EET mechanisms that exist in the genus Geobacter and point to the possibility of sRNA in modulating EET gene expression.</p
Table_4_Transcriptomic, Proteomic, and Bioelectrochemical Characterization of an Exoelectrogen Geobacter soli Grown With Different Electron Acceptors.xlsx
<p>The ability of Geobacter species to transfer electrons outside cells enables them to play an important role in biogeochemical and bioenergy processes. Our knowledge of the extracellular electron transfer (EET) process in the genus Geobacter is mainly from the study of G. sulfurreducens, and in order to fully investigate the EET mechanisms in the genus Geobacter, other Geobacter species should also be considered. This study focused on the EET of Geobacter soli GSS01, which exhibited a capability of reducing insoluble Fe(III) oxides and generating electrical current comparable with G. sulfurreducens PCA. Electrochemical characterization, including cyclic voltammetry, differential pulse voltammetry, and electrochemical in situ FTIR spectra, revealed that different redox proteins contributed to the electrochemical behaviors of G. soli and G. sulfurreducens. Based on comparative transcriptomic and proteomic analyses, OmcS was the most upregulated protein in both G. soli and G. sulfurreducens cells grown with insoluble Fe(III) oxides vs. soluble electron acceptor. However, the proteins including OmcE and PilA that were previously reported as being important for EET in G. sulfurreducens were downregulated or unchanged in G. soli cells grown with insoluble electron acceptors vs. soluble electron acceptor, and many proteins that were upregulated in G. soli cells grown with insoluble electron acceptors vs. soluble electron acceptor, such as OmcN, are not important for EET in G. sulfurreducens. We also identified 30 differentially expressed small RNAs (sRNAs) in G. soli cells grown with different acceptors. Taken together, these findings help to understand the versatile EET mechanisms that exist in the genus Geobacter and point to the possibility of sRNA in modulating EET gene expression.</p