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Yang Tan, Ramesh Y Adhikari, Nikhil S Malvankar, Joy E Ward, Trevor L Woodard, Kelly P Nevin, Derek R Lovley
: The electrically conductive pili (e-pili) of Geobacter sulfurreducens serve as a model for a novel strategy for long-range extracellular electron transfer. e-pili are also a new class of bioelectronic materials. However, the only other Geobacter pili previously studied, which were from G. uraniireducens, were poorly conductive. In order to obtain more information on the range of pili conductivities in Geobacter species, the pili of G. metallireducens were investigated. Heterologously expressing the PilA gene of G...
January 17, 2017: MBio
Ana P Fernandes, Tiago C Nunes, Catarina M Paquete, Carlos A Salgueiro
Geobacter bacteria usually prevail among other microorganisms in soils and sediments where Fe(III) reduction has a central role. This reduction is achieved by extracellular electron transfer, where the electrons are exported from the interior of the cell to the surrounding environment. Periplasmic cytochromes play an important role in establishing an interface between inner and outer membrane electron transfer components. In addition, periplasmic cytochromes, in particular nanowire cytochromes that contain at least 12 haem groups, have been proposed to play a role in electron storage in conditions of environmental lack of electron acceptors...
January 16, 2017: Biochemical Journal
Anna Prokhorova, Katrin Sturm-Richter, Andreas Doetsch, Johannes Gescher
: Anode-associated multi-species exoelectrogenic biofilms are essential to the function of bioelectrochemical systems (BESs). The individual activities of anode associated organisms and physiological responses resulting from co-culturing are often hard to assess due to the high microbial diversity in these systems. Therefore, we developed a model multispecies biofilm of the three exoelectrogenic proteobacteria Shewanella oneidensis, Geobacter sulfurreducens and Geobacter metallireducens with the aim to study in detail the biofilm formation dynamics, the interactions between the organisms and the overall activity of an exoelectrogenic biofilm as a consequence of the applied anode potential...
January 13, 2017: Applied and Environmental Microbiology
Souichiro Kato
Geobacter species are capable of utilizing solid-state compounds, including anodic electrodes, as electron acceptors of respiration via extracellular electron transfer (EET) and have attracted considerable attention for their crucial role as biocatalysts of bioelectrochemical systems (BES's). Recent studies disclosed that anode potentials affect power output and anodic microbial communities, including selection of dominant Geobacter species, in various BES's. However, the details in current-generating properties and responses to anode potentials have been investigated only for a model species, namely Geobacter sulfurreducens...
January 6, 2017: International Journal of Molecular Sciences
Phuc T Ha, Stephen R Lindemann, Liang Shi, Alice C Dohnalkova, James K Fredrickson, Michael T Madigan, Haluk Beyenal
Microbial phototrophs, key primary producers on Earth, use H2O, H2, H2S and other reduced inorganic compounds as electron donors. Here we describe a form of metabolism linking anoxygenic photosynthesis to anaerobic respiration that we call 'syntrophic anaerobic photosynthesis'. We show that photoautotrophy in the green sulfur bacterium Prosthecochloris aestaurii can be driven by either electrons from a solid electrode or acetate oxidation via direct interspecies electron transfer from a heterotrophic partner bacterium, Geobacter sulfurreducens...
January 9, 2017: Nature Communications
Leonor Morgado, Marta Bruix, P Raj Pokkuluri, Carlos A Salgueiro, David L Turner
The periplasmic triheme cytochrome PpcA from Geobacter sulfurreducens is highly abundant; it is the likely reservoir of electrons to the outer surface to assist the reduction of extracellular terminal acceptors; these include insoluble metal oxides in natural habitats and electrode surfaces from which electricity can be harvested. A detailed thermodynamic characterization of PpcA showed that it has an important redox-Bohr effect that might implicate the protein in e(-)/H(+) coupling mechanisms to sustain cellular growth...
January 15, 2017: Biochemical Journal
Synthia Maes, Ruben Props, Jeffrey P Fitts, Rebecca De Smet, Frank Vanhaecke, Nico Boon, Tom Hennebel
The widespread use of platinum in high-tech and catalytic applications has led to the production of diverse Pt loaded wastewaters. Effective recovery strategies are needed for the treatment of low concentrated waste streams to prevent pollution and to stimulate recovery of this precious resource. The biological recovery of five common environmental Pt-complexes was studied under acidic conditions; the chloro-complexes PtCl42- and PtCl62-, the amine-complex Pt(NH3)4Cl2 and the pharmaceutical complexes cisplatin and carboplatin...
2017: PloS One
Caleb E Levar, Colleen L Hoffman, Aubrey J Dunshee, Brandy M Toner, Daniel R Bond
Geobacter sulfurreducens uses at least two different pathways to transport electrons out of the inner membrane quinone pool before reducing acceptors beyond the outer membrane. When growing on electrodes poised at oxidizing potentials, the CbcL-dependent pathway operates at or below redox potentials of -0.10 V vs the standard hydrogen electrode, whereas the ImcH-dependent pathway operates only above this value. Here, we provide evidence that G. sulfurreducens also requires different electron transfer proteins for reduction of a wide range of Fe(III)- and Mn(IV)-(oxyhydr)oxides, and must transition from a high- to low-potential pathway during reduction of commonly studied soluble and insoluble metal electron acceptors...
January 3, 2017: ISME Journal
Hui Yu, Hui Wan, Chunhua Feng, Xiaoyun Yi, Xiaoping Liu, Yuan Ren, Chaohai Wei
The necessity for developing an efficient and cost-effective in situ bioremediation technology for sediments contaminated with polychlorinated biphenyls (PCBs) has prompted the application of low-voltage electrical fields to anaerobic digestion systems. Here we show that the use of a sediment-based bio-electrochemical reactor (BER) poised at a potential of -0.50V (vs. a standard calomel electrode, SCE) substantially enhanced the reduction of 2,3,4,5-tetrachlorobiphenyl (PCB 61) when acetate was added as a carbon source...
December 27, 2016: Science of the Total Environment
Juliana B Müller, Débora T Ramos, Catherine Larose, Marilda Fernandes, Helen S C Lazzarin, Timothy M Vogel, Henry X Corseuil
The use of biodiesel as a transportation fuel and its growing mandatory blending percentage in diesel increase the likelihood of contaminating groundwater with diesel/biodiesel blends. A 100L-field experiment with B20 (20% biodiesel and 80% diesel, v/v) was conducted to assess the potential for the combined biostimulation of iron and sulfate reducing bacteria to enhance BTEX and PAH biodegradation in a diesel/biodiesel blend-contaminated groundwater. A B20 field experiment under monitored natural attenuation (MNA) was used as a baseline control...
December 5, 2016: Journal of Hazardous Materials
Daisuke Sasaki, Kengo Sasaki, Yota Tsuge, Akihiko Kondo
The metabolic state of microflora (mixed microbial cultures) in microbial fuel cells (MFCs) is currently unclear. Metabolomic analyses were conducted of microflora growing on the anodic electrodes of MFCs operated at pH 7.0, 5.5, or 4.0 and utilizing starch as the major carbon substrate. A much higher current was produced at pH 7.0 than at pH 5.5 and 4.0, correlating with an increased population ratio of Geobacter species to the total bacteria growing on the electrode. Most intracellular metabolites related to the tricarboxylic acid (TCA) cycle were present at a higher level at pH 7...
December 2016: AMB Express
Jing Ding, Yong-Ze Lu, Liang Fu, Zhao-Wei Ding, Yang Mu, Shuk H Cheng, Raymond J Zeng
Anaerobic oxidation of methane (AOM) contributes significantly to the global methane sink. Previously, studies of anaerobic methanotrophic (ANME) archaea have been limited as they have not been separable from their bacterial partners during the AOM process because of their dependence on the bacteria. A microbial fuel cell (MFC) is a device capable of directly transforming chemical energy to electrical energy via electrochemical reactions involving biochemical pathways. In this study, decoupling of denitrifying anaerobic methane oxidation (DAMO) archaea and DAMO bacteria was investigated in an microbial fuel cell (MFC) using methane as the fuel...
December 9, 2016: Water Research
Dongdong Zhang, Zhiling Li, Chunfang Zhang, Xue Zhou, Zhixing Xiao, Takanori Awata, Arata Katayama
A microbial fuel cell (MFC), with graphite electrodes as both the anode and cathode, was operated with a soil-free anaerobic consortium for phenol degradation. This phenol-degrading MFC showed high efficiency with a current density of 120 mA/m(2) and a coulombic efficiency of 22.7%, despite the lack of a platinum catalyst cathode and inoculation of sediment/soil. Removal of planktonic bacteria by renewing the anaerobic medium did not decrease the performance, suggesting that the phenol-degrading MFC was not maintained by the planktonic bacteria but by the microorganisms in the anode biofilm...
December 12, 2016: Journal of Bioscience and Bioengineering
Xun Xu, Qingliang Zhao, Mingsong Wu, Jing Ding, Weixian Zhang
To enhance the biodegradation of organic matter in sediment microbial fuel cell (SMFC), Fe(III) oxide, as an alternative electron acceptor, was added into the sediment. Results showed that the SMFC with Fe(III) oxide addition obtained higher removal efficiencies for organics than the SMFC without Fe(III) oxide addition and open circuit bioreactor, and produced a maximum power density (Pmax) of 87.85mW/m(2) with a corresponding maximum voltage (Vmax) of 0.664V. The alteration of UV-254 and specific ultraviolet absorbance (SUVA) also demonstrated the organic matter in sediments can be effectively removed...
February 2017: Bioresource Technology
Shu Takahashi, Morio Miyahara, Atsushi Kouzuma, Kazuya Watanabe
BACKGROUND: Rice bran is a by-product of the rice milling process and mostly discarded in Japan. Although many studies have shown that microbial fuel cells (MFCs) are able to generate electricity from organic wastes, limited studies have examined MFCs for generating electricity from rice bran. FINDINGS: Laboratory-scale single-chamber MFCs were inoculated with paddy field soil and supplied with rice bran for examining electricity generation. Power outputs and microbiome compositions were compared between MFCs containing pure water as the liquid phase (MFC-W) and those containing mineral solution (MFC-M)...
2016: Bioresources and Bioprocessing
Yan Dang, David J F Walker, Kaitlin E Vautour, Steven Dixon, Dawn E Holmes
: Insight into the mechanisms for arsenic detoxification by Geobacter species is expected to improve the understanding of global cycling of arsenic in iron rich subsurface sedimentary environments. Analysis of fourteen different Geobacter genomes showed that all of these species have genes coding for an arsenic detoxification system (ars operon), and several have genes required for arsenic respiration (arr operon) and methylation (arsM). Four arsenic repressor-like proteins were detected in the genome of G sulfurreducens, however, only one (ArsR1) regulated transcription of the ars operon...
December 9, 2016: Applied and Environmental Microbiology
Ananda Rao Hari, Krishna P Katuri, Bruce E Logan, Pascal E Saikaly
Anode potential has been shown to be a critical factor in the rate of acetate removal in microbial electrolysis cells (MECs), but studies with fermentable substrates and set potentials are lacking. Here, we examined the impact of three different set anode potentials (SAPs; -0.25, 0, and 0.25 V vs. standard hydrogen electrode) on the electrochemical performance, electron flux to various sinks, and anodic microbial community structure in two-chambered MECs fed with propionate. Electrical current (49-71%) and CH4 (22...
December 9, 2016: Scientific Reports
Akio Ueno, Satoru Shimizu, Mikako Hashimoto, Takumi Adachi, Takako Matsushita, Hidetoshi Okuyama, Kiyohito Yoshida
Geobacter spp., regarded as strict anaerobes, have been reported to grow under aerobic conditions. To elucidate the role of fatty acids in aerobiosis of Geobacter spp., we studied the effect of aerobiosis on fatty acid composition and turnover in G. bemidjiensis Bem(T). G. bemidjiensis Bem(T) was grown under the following different culture conditions: anaerobic culture for 4 days (type 1) and type 1 culture followed by 2-day anaerobic (type 2) or aerobic culture (anaerobic-to-aerobic shift; type 3). The mean cell weight of the type 3 culture was approximately 2...
December 8, 2016: Journal of Oleo Science
Akihiro Okamoto, Yoshihide Tokunou, Junki Saito
Outer-membrane c-type cytochrome (OM c-Cyt) complexes in several genera of iron-reducing bacteria, such as Shewanella and Geobacter, are capable of transporting electrons from the cell interior to extracellular solids as a terminal step of anaerobic respiration. The kinetics of this electron transport has implications for controlling the rate of microbial electron transport during bioenergy or biochemical production, iron corrosion, and natural mineral cycling. Herein, we review the findings from in-vivo and in-vitro studies examining electron transport kinetics through single OM c-Cyt complexes in Shewanella oneidensis MR-1...
2016: Biophysics and Physicobiology
Takahiro Yamashita, Natsuki Ookawa, Mitsuyoshi Ishida, Hiroyuki Kanamori, Harumi Sasaki, Yuichi Katayose, Hiroshi Yokoyama
Biochemical oxygen demand (BOD) is a widely used index of water-quality assessment. Since bioelectrochemical BOD biosensors require anaerobic conditions for anodic reactions, they are not directly used in aerobic environments such as aeration tanks. Normally, the BOD biosensors are closed-type, where the anode is packed inside a closed chamber to avoid exposure to oxygen. In this study, a novel bioelectrochemical open-type biosensor was designed for in-situ monitoring of BOD during intermittent aeration. The open-type anode, without any protection against exposure to oxygen, was directly inserted into an intermittently aerated tank filled with livestock wastewater...
December 5, 2016: Scientific Reports
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