Xin Wang, Yujie Feng, Elle Wang et al.

Journal of Biotechnology • 2008

Ruud A. Timmers, David P.B.T.B. Strik, Hubertus V.M. Hamelers et al.

Biomass and Bioenergy • 2013

Guodong Zhang, Qingliang Zhao, Yan Jiao et al.

Water Research • 2011

Microbial fuel cells (MFCs) with abiotic cathodes require expensive catalyst (such as Pt) or catholyte (such as hexacynoferrate) to facilitate oxidation reactions. This study incorporated biocathodes into a three-chamber MFC to yield electricity from sewage sludge at maximum power output of 13.2 ± 1.7 W/m(3) during polarization, much higher than those previously reported. After 15 d operation, the total chemical oxygen demand (TCOD) removal and coulombic efficiency (CE) of cell reached 40.8 ± 9.0% and 19.4 ± 4.3%, respectively. The anolyte comprised principally acetate and propionate (minor) as metabolites. The use of biocathodes produced an internal resistance of 36-46 Ω, lower than those reported in literature works, hence yielding higher maximum power density from MFC. The massively parallel sequencing technology, 454 pyrosequencing technique, was adopted to probe microbial community on anode biofilm, with dominant phyla belonging to Proteobacteria (45% of total bacteria), Bacteroidetes (19%), Uncultured bacteria (9%), Actinobacteria (7%), Firmicutes (7%), Chloroflex (7%). At genera level, Rhodoferax, Ferruginibacter, Propionibacterium, Rhodopseudomonas, Ferribacterium, Clostridium, Chlorobaculum, Rhodobacter, Bradyrhizobium were the abundant taxa (relative abundances>2.0%).

Abhilasha Singh Mathuriya

Environmental Technology • 2013

Experiments were designed to evaluate the influence of various anaerobic inoculums to enhance microbial fuel cell (MFC) performance utilizing tannery wastewater as substrate. Three bacterial electrogenic strains, tolerant to tannery environment, were isolated from soil contaminated with tannery waste and tannery wastewater was inoculated with these monotypes and mixed consortia of three bacterial strains in different MFCs. Comparative analysis was made by treating the tannery wastewater with foreign microbial consortia (activated sludge inoculum) and with only natural habitat microbes already present in plain wastewater. It was observed that inoculum contributes great effect on the MFC performance. Among the studied inoculation strategies, mixed electrogenic strain inocula enabled higher current yield along with concurrent substrate removal efficiency. On the contrary, plain wastewater resulted in relatively low efficiency.

Yujie Feng, He Lee, Xin Wang et al.

Bioresource Technology • 2009

A baffled air-cathode microbial fuel cell (BAFMFC) was designed and operated under continuous flow. With glucose fed as substrate, an average voltage of 652 mV was obtained under the external resistance of 1000 Omega (30 degrees C). The maximum power density was 15.2 W/m(3) with the chemical oxygen demand (COD) removal rate of 88.0%. The overall resistance was 13.7 Omega while ohmic internal resistance was 10.8 Omega. Average COD removal rate was 69.7-88.0%, when COD loading varied from 4.11 kg COD/(m(3)NACd) to 16.0 kg COD/(m(3)NACd). The liquid from corn stover steam explosion process (COD=7160+/-50mg/L) was treated by BAFMFC, and the maximum power density was 10.7 W/m(3) with the average COD removal rate was 89.1%. The present study indicated BAFMFC can be comparable to the traditional anaerobic baffled reactor in COD removal rate for high-concentration wastewater and have an advantage in energy harvest from wastewater.

Stefano Freguia, Masaki Masuda, Seiya Tsujimura et al.

Bioelectrochemistry • 2009

Lactococcus lactis is a gram-positive, normally homolactic fermenter that is known to produce several kinds of membrane associated quinones, which are able to mediate electron transfer to extracellular electron acceptors such as Fe(3+), Cu(2+) and hexacyanoferrate. Here we show that this bacterium is also capable of performing extracellular electron transfer to anodes by utilizing at least two soluble redox mediators, as suggested by the two-step catalytic current developed. One of these two mediators was herein suggested to be 2-amino-3-dicarboxy-1,4-naphthoquinone (ACNQ), via evaluation of standard redox potential, ability of the bacterium to exploit the quinone when exogenously provided, as well as by high performance liquid chromatography coupled with UV spectrum analysis. During electricity generation, L. lactis slightly deviated from its normal homolactic metabolism by excreting acetate and pyruvate in stoichiometric amounts with respect to the electrical current. In this metabolism, the anode takes on the role of electron sink for acetogenic fermentation. The finding that L. lactis self-catalyses anodic electron transfer by excretion of redox mediators is remarkable as the mechanisms of extracellular electron transfer by pure cultures of gram-positive bacteria had previously never been elucidated.

P. Mehta, A. Hussain, B. Tartakovsky et al.

Enzyme and Microbial Technology • 2010

Electricity production from carbon monoxide (CO) is demonstrated in a single chamber microbial fuel cell (MFC) with a CoTMPP-based air cathode. The MFC was inoculated with anaerobic sludge and continuously sparged with CO as a sole carbon source. Volumetric power output was maximized at a CO flow rate of 4.8LLR(-1)d(-1) reaching 6.4mWLR(-1). Several soluble and gaseous degradation products including hydrogen, methane, and acetate were detected, resulting in a relatively low apparent Coulombic efficiency of 8.7%. Tests also demonstrated electricity production from hydrogen and acetate with the highest and fastest increase in voltage exhibited after acetate injection. It is hypothesized that electricity generation in a CO-fed MFC is accomplished by a consortium of carboxydotrophic and carbon monoxide - tolerant anodophilic microorganisms.

Weiqing Li, Shaohui Zhang, Gang Chen et al.

Applied Energy • 2014

A double-chamber denitrifying microbial fuel cell (MFC), using boric acid-borate buffer solution as an alternative to phosphate buffer solution, was set up to investigate the influence of buffer solution concentration, temperature and external resistance on electricity generation and pollutant removal efficiency. The result revealed that the denitrifying MFC with boric acid-borate buffer solution was successfully started up in 51 days, with a stable cell voltage of 205.1 ± 1.96 mV at an external resistance of 50 Ω. Higher concentration of buffer solution favored nitrogen removal and electricity generation. The maximum power density of 8.27 W/m(3) net cathodic chamber was obtained at a buffer solution concentration of 100 mmol/L. An increase in temperature benefitted electricity generation and nitrogen removal. A suitable temperature for this denitrifying MFC was suggested to be 25 °C. Decreasing the external resistance favored nitrogen removal and organic matter consumption by exoelectrogens.

A. Hamzah, N. H. Ridzuan, S. Radiman

3rd Annual International Conference on Advances in Biotechnology (BioTech 2013) • 2013

Yong Luo, Renduo Zhang, Guangli Liu et al.

Journal of Hazardous Materials • 2010

Indole is a typical refractory and inhibitory compound present in coking wastewater. The aim of this study was to investigate possible electricity generation with indole degradation in the microbial fuel cell (MFC). Experiments were conducted in two types of the MFC: a continuous-fed MFC (C-MFC) and a batch-fed MFC (B-MFC). In the C-MFC, the maximum power densities reached 45.4, 51.2, and 2.1 W/m(3), respectively, from using 1000 mg/L glucose, a mixture of 1000 mg/L glucose and 250 mg/L indole, and 250 mg/L indole as the fuel. When using 250 mg/L indole as the fuel, the removal efficiency of indole was up to 88% within 3 h. Increasing indole concentrations from 250 to 1500 mg/L resulted in decrease of the maximum power densities from 2.1 to 0.8 W/m(3), and average degradation rates from 41.7 to 8.9 mg/(Lh). Compared with the C-MFC, the B-MFC increased the maximum power densities from 2.1 to 3.3 W/m(3) and the coulombic efficiencies from 0.7% to 81.5%. Microbial community analyses showed that the addition of indole obviously changes the microbial community of the anode electrode, including the changes of relative abundance and emergence of new species. The results should be useful for treatment of wastewater containing indole.

Seung Won Lee, Bo Young Jeon, Doo Hyun Park

Biotechnology Letters • 2010

A single-compartmented microbial fuel cell composed of a graphite felt anode modified with Neutral Red (NR-anode) and a porous Fe(II)-carbon cathode (FeC-cathode) were compared for electricity generation from Microbacterium sp. and Pseudomonas sp. under identical conditions. Pseudomonas sp. was more than four times the size of Microbacterium sp. based on SEM images. In cyclic voltammetry, the redox reaction between Microbacterium sp and electrode was three times the rate observed between Pseudomonas sp. and the electrode based on the Y-axis (current) variation of cyclic voltammogram. The electric power generated by Microbacterium sp. was approx 3-4 times higher than that with Pseudomonas sp. during incubation for more than 150 days in the fuel cell.

M. Behera, M. M. Ghangrekar

Water Science and Technology • 2011

Performance of four microbial fuel cells (MFC-1, MFC-2, MFC-3 and MFC-4) made up of earthen pots with wall thicknesses of 3, 5, 7 and 8.5 mm, respectively, was evaluated. The MFCs were operated in fed batch mode with synthetic wastewater having sucrose as the carbon source. The power generation decreased with increase in the thickness of the earthen pot which was used to make the anode chamber. MFC-1 generated highest sustainable power density of 24.32 mW/m2 and volumetric power of 1.04 W/m3 (1.91 mA, 0.191 V) at 100 Ω external resistance. The maximum Coulombic efficiencies obtained in MFC-1, MFC-2, MFC-3 and MFC-4 were 7.7, 7.1, 6.8 and 6.1%, respectively. The oxygen mass transfer and oxygen diffusion coefficients measured for earthen plate of 3 mm thickness were 1.79 × 10−5 and 5.38 × 10−6 cm2/s, respectively, which implies that earthen plate is permeable to oxygen as other polymeric membranes. The internal resistance increased with increase in thickness of the earthen pot MFCs. The thickness of the earthen material affected the overall performance of MFCs.

Mi-Sun Kim

Journal of Microbiology and Biotechnology • 2012

In this study, we investigated various cultural and operational factors to enhance electricity generation in a microbial fuel cell (MFC) using Geobacter sulfurreducens. The pure culture of G. sulfurreducens was cultivated using various substrates including acetate, malate, succinate, and butyrate, with fumarate as an electron acceptor. Cell growth was observed only in acetate-fed medium, when the cell concentrations increased 4-fold for 3 days. A high acetate concentration suppressed electricity generation. As the acetate concentration was increased from 5 to 20 mM, the power density dropped from 16 to 13 mW/m2, whereas the coulombic efficiency (CE) declined by about half. The immobilization of G. sulfurreducens on the anode considerably reduced the enrichment period from 15 to 7 days. Using argon gas to create an anaerobic condition in the anode chamber led to increased pH, and electricity generation subsequently dropped. When the plain carbon paper cathode was replaced by Pt-coated carbon paper (0.5 mg Pt/cm2), the CE increased greatly from 39% to 83%.

Jeongdong Choi, Youngho Ahn

Journal of Environmental Management • 2013

This study examined the continuous performance of air cathode MFC stacks for domestic wastewater treatments at two different temperatures (23 ± 3 °C and 30 ± 1 °C) and organic loading rates to determine the effects of the electrode connection and hydraulic flow mode on the stack performance. The power density and process stability were affected significantly by the electrode connection type, flow mode, and operating parameters. The parallel electrode connection system (in series flow mode) had benefits of COD removal, Coulombic efficiency and maximal power density due to the higher stability of the ORP in overall cells. The highest power density of 420 mW/m(2) (12.8 W/m(3)) was achieved in series flow and parallel connection mode at an organic loading rate of 25.6 g COD/L-d (HRT of 0.33 h) under mesophilic conditions, achieving a COD removal of 44%. The results highlight the importance of prefermentation process in the application of a stacked MFC for an actual wastewater treatment.

Jaecheul Yu, Jiyun Seon, Younghyun Park et al.

Bioresource Technology • 2012

A submerged type microbial fuel cell (MFC) system, which consisted of six readily exchangeable air-cathode MFCs, was evaluated for continuous treatment of low-strength domestic wastewater. When supplied with synthetic wastewater (COD 100 mg/L), the system showed increasing maximum power densities from 191 to 754 mW/m2 as COD loading rates increased (0.20-0.40 kg/m3/day). COD removal efficiencies decreased with increased COD loading rates but the effluent COD concentrations met the relevant effluent quality standard (CODMn 20 mg/L) at all conditions. The system was then operated with domestic wastewater (c.a. 100 mg COD/L) at 0.32 and 0.43 kg/m3/day. The system showed much lower power densities (116-149 mW/m2) at both loading rates, compared to synthetic wastewater. Anodic microbial communities were completely different when the wastewater type was changed. These results suggest that the newly developed MFC system could be applied to treat low-strength domestic wastewater without requiring any additional organic removal stage.

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Journal of Biochemical Technology • 2012

Kangping Cui, Ye Wang, Shiqun Sun

2010 Asia-Pacific Power and Energy Engineering Conference • 2010

Paniz Izadi, Mostafa Rahimnejad

Biofuel Research Journal • 2014

Guangyi Zhang, Hanmin Zhang, Yanjie Ma et al.

Enzyme and Microbial Technology • 2014

Conductive materials with attached biofilms, were used as membrane filtration biocathodes to filter the effluent and supply electrons for denitrification. Stainless steel mesh and carbon felt were employed to fabricate membrane modules, and the two MFC systems were termed as M1 and M2, respectively. High effluent quality was obtained with M1 and M2 in terms of turbidity, COD and ammonium. In M1, no bioelectrochemical denitrification took place, while nitrate decreased from 35.88±4.15 to 27.33±5.32mg-N/L through the membrane in M2, causing a removal efficiency of 23.3±6.5% with respect to cathodic nitrate. The denitrification ceased without electricity. The maximum power densities of M1 and M2 were 121 and 1253mW/m(3), respectively. Micrococcus bacteria and rod-shaped bacteria covered the surface of carbon felt and fewer bacteria were found on stainless steel mesh. According to fluorescence in situ hybridization, the putative bacteria affiliated with Paracoccus genus and Pseudomonas spp. dominated in the interior biofilm on carbon felt for denitrification. Results demonstrate that the carbon felt system can perform bioelectrochemical denitrification to polish the effluent.

Zhiqiang Hu

Journal of Power Sources • 2008

Seyed Kamran Foad Marashi, Hamid-Reza Kariminia

2012 Second Iranian Conference on Renewable Energy and Distributed Generation • 2012

Wen-Wei Li, Guo-Ping Sheng, Han-Qing Yu

Food Industry Wastes • 2013

Yifeng Zhang, Booki Min, Liping Huang et al.

Bioresource Technology • 2010

The effect of substrate changes on the performance and microbial community of two-chamber microbial fuel cells (MFCs) was investigated in this study. The MFCs enriched with a single substrate (e.g., acetate, glucose, or butyrate) had different acclimatization capability to substrate changes. The MFC enriched with glucose showed rapid and higher power generation, when glucose was switched with acetate or butyrate. However, the MFC enriched with acetate needed a longer adaptation time for utilizing glucose. Microbial community was also changed when the substrate was changed. Clostridium and Bacilli of phylum Firmicutes were detected in acetate-enriched MFCs after switching to glucose. By contrast, Firmicutes completely disappeared and Geobacter-like species were specifically enriched in glucose-enriched MFCs after feeding acetate to the reactor. This study further suggests that the type of substrate fed to MFC is a very important parameter for reactor performance and microbial community, and significantly affects power generation in MFCs.

Wenguo Wu, Fei Yang, Xing Liu et al.

Microbial Cell Factories • 2014

The substrate, serving as carbon and energy source, is one of the major factors affecting the performance of microbial fuel cells (MFCs). We utilized BIOLOG system to rapidly screen substrates for electricigens, and further evaluated influence of these substrates on electricity generation of Shewanella loihica PV-4 in MFCs.

Harry J. Dudley, Zhiyong Jason Ren, David M. Bortz

ARXIV • 2019

Microbial electrolysis cells (MECs) employ electroactive bacteria to perform extracellular electron transfer, enabling hydrogen generation from biodegradable substrates. In previous work, we developed and analyzed a differential-algebraic equation (DAE) model for MECs. The model resembles a chemostat with ordinary differential equations (ODEs) for concentrations of substrate, microorganisms, and an extracellular mediator involved in electron transfer. There is also an algebraic constraint for electric current and hydrogen production. Our goal is to determine the outcome of competition between methanogenic archaea and electroactive bacteria, because only the latter contribute to electric current and resulting hydrogen production. We investigate asymptotic stability in two industrially relevant versions of the model. An important aspect of chemostats models is the principle of competitive exclusion -- only microbes which grow at the lowest substrate concentration will survive as $t\to\infty$. We show that if methanogens grow at the lowest substrate concentration, then the equilibrium corresponding to competitive exclusion by methanogens is globally asymptotically stable. The analogous result for electroactive bacteria is not necessarily true. We show that local asymptotic stability of exclusion by electroactive bacteria is not guaranteed, even in a simplified version of the model. In this case, even if electroactive bacteria can grow at the lowest substrate concentration, a few additional conditions are required to guarantee local asymptotic stability. We also provide numerical simulations supporting these arguments. Our results suggest operating conditions that are most conducive to success of electroactive bacteria and the resulting current and hydrogen production in MECs. This will help identify when methane production or electricity and hydrogen production are favored.

Sota Ihara, Satoshi Wakai, Tomoko Maehara et al.

Microorganisms • 2022

Ultramicrobacteria (UMB) that can pass through a 0.22 µm filter are attractive because of their novelty and diversity. However, isolating UMB has been difficult because of their symbiotic or parasitic lifestyles in the environment. Some UMB have extracellular electron transfer (EET)-related genes, suggesting that these symbionts may grow on an electrode surface independently. Here, we attempted to culture from soil samples bacteria that passed through a 0.22 µm filter poised with +0.2 V vs. Ag/AgCl and isolated Cellulomonas sp. strain NTE-D12 from the electrochemical reactor. A phylogenetic analysis of the 16S rRNA showed 97.9% similarity to the closest related species, Cellulomonas algicola, indicating that the strain NTE-D12 is a novel species. Electrochemical and genomic analyses showed that the strain NTE-D12 generated the highest current density compared to that in the three related species, indicating the presence of a unique electron transfer system in the strain. Therefore, the present study provides a new isolation scheme for cultivating and isolating novel UMB potentially with a symbiotic relationship associated with interspecies electron transfer.

Li Xie, Naoko Yoshida, Shun’ichi Ishii et al.

Microorganisms • 2021

In this study, a novel electrogenic bacterium denoted as strain NIT-T3 of the genus Desulfuromonas was isolated from a graphene-oxide-reducing enrichment culture that was originally obtained from a mixture of seawater and coastal sand. Strain NIT-T3 utilized hydrogen and various organic acids as electron donors and exhibited respiration using electrodes, ferric iron, nitrate, and elemental sulfur. The strain contained C16:1ω7c, C16:0, and C15:0 as major fatty acids and MK-8, 9, and 7 as the major respiratory quinones. Strain NIT-T3 contained four 16S rRNA genes and showed 95.7% similarity to Desulfuromonasmichiganensis BB1T, the closest relative. The genome was 4.7 Mbp in size and encoded 76 putative c-type cytochromes, which included 6 unique c-type cytochromes (<40% identity) compared to those in the database. Based on the physiological and genetic uniqueness, and wide metabolic capability, strain NIT-T3 is proposed as a type strain of ‘Desulfuromonas versatilis’ sp. nov.

György Schneider, Dorina Pásztor, Péter Szabó et al.

Microorganisms • 2023

To develop efficient microbial fuel cell systems for green energy production using different waste products, establishing characterised bacterial consortia is necessary. In this study, bacteria with electrogenic potentials were isolated from mud samples and examined to determine biofilm-formation capacities and macromolecule degradation. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry identifications have revealed that isolates represented 18 known and 4 unknown genuses. They all had the capacities to reduce the Reactive Black 5 stain in the agar medium, and 48 of them were positive in the wolfram nanorod reduction assay. The isolates formed biofilm to different extents on the surfaces of both adhesive and non-adhesive 96-well polystyrene plates and glass. Scanning electron microscopy images revealed the different adhesion potentials of isolates to the surface of carbon tissue fibres. Eight of them (15%) were able to form massive amounts of biofilm in three days at 23 °C. A total of 70% of the isolates produced proteases, while lipase and amylase production was lower, at 38% and 27% respectively. All of the macromolecule-degrading enzymes were produced by 11 isolates, and two isolates of them had the capacity to form a strong biofilm on the carbon tissue one of the most used anodic materials in MFC systems. This study discusses the potential of the isolates for future MFC development applications.

Orcan Demircan, Abdul Razaque Memon

Turkish Journal of Agriculture - Food Science and Technology • 2022

Heavy metal pollution generally occurs due to socio-economic, industrial, and anthropogenic activities, which may cause an environmentally hazardous and serious severe threat to the survival of the organisms (genotoxic, carcinogenic, and clastogenic effects on it). Many physical and chemical remediation approaches have been proposed to deal with this pollution, but these are very time-consuming and costly. While bioremediation stands out as an inexpensive and efficient approach, the use of bacteria is thought to be a potential and productive organism to prevent this pollution. This review has evaluated the bacterial potential to clean up heavy metals from the environment and elucidated the mechanisms responsible for bioremediation.

Marta A. Silva, Pilar C. Portela, Carlos A. Salgueiro

Biochemical Journal • 2021

The redox potential values of cytochromes can be modulated by the protonation/deprotonation of neighbor groups (redox-Bohr effect), a mechanism that permits the proteins to couple electron/proton transfer. In the respiratory chains, this effect is particularly relevant if observed in the physiological pH range, as it may contribute to the electrochemical gradient for ATP synthesis. A constitutively produced family of five triheme cytochromes (PpcA−E) from the bacterium Geobacter sulfurreducens plays a crucial role in extracellular electron transfer, a hallmark that permits this bacterium to be explored for several biotechnological applications. Two members of this family (PpcA and PpcD) couple electron/proton transfer in the physiological pH range, a feature not shared with PpcB and PpcE. That ability is crucial for G. sulfurreducens’ growth in Fe(III)-reducing habitats since extra contributors to the electrochemical gradient are needed. It was postulated that the redox-Bohr effect is determined by the nature of residue 6, a leucine in PpcA/PpcD and a phenylalanine in PpcB/PpcE. To confirm this hypothesis, Phe6 was replaced by leucine in PpcB and PpcE. The functional properties of these mutants were investigated by NMR and UV–visible spectroscopy to assess their capability to couple electron/proton transfer in the physiological pH range. The results obtained showed that the mutants have an increased redox-Bohr effect and are now capable of coupling electron/proton transfer. This confirms the determinant role of the nature of residue 6 in the modulation of the redox-Bohr effect in this family of cytochromes, opening routes to engineer Geobacter cells with improved biomass production.

Yue Zhu

Highlights in Science, Engineering and Technology • 2022

The use of bacteria to degrade heavy soil metal concentrations and boost plant tolerance to elevated metal levels has significant ecological and financial benefits. Soil contaminated with heavy metals may cause a variety of problems. First, the soil respiration is affected by the heavy metal content because of the way it affects the respiration, metabolism (the metabolic entropy response), and activity of soil microbes. There is less organic carbon converted to bio-carbon and higher microbial metabolic entropy in metal-contaminated soil. Last but not least, heavy metals may be absorbed by seeds, leading to physiological dysfunction and malnutrition in the developing plant. Having an excess of metals in the body might be dangerous. Therefore, the use of bacterial which use various mechanism to degrade heavy metals is the best approach of this paper in getting reed of the heavy metals in soil.

Makwin Danladi Makut, Toyosi Michelle Adebayo, Jibril Egwu Owuna

BIOMED Natural and Applied Science • 2022

Background: The presence of spent hydrocarbon in soil is a serious problem to the environment hence study on bioremediation of soil polluted with auto-mechanic oil in Abuja Metropolis was carried out. Methods: A total of twenty (20) soil samples were collected, bacteria were isolated from the contaminated soil and identified using standard microbiological methods. The spent hydrocarbon utilization was determined using Atomic Adsorption UV Spectrometer. Results: The total viable count of the bacteria was 1.07 x 106 from Apo Mechanic village, 1.10 x 106 from Utako Mechanic workshops, 0.40 x 106 from Gwarinpa Mechanic workshops and 2.04 x 106 from Area one Mechanic workshops. The percentage occurrence of bacteria from Apo Mechanic village was Enterobacter species 40.0%, Pseudomonas synxantha 60.0%, Bacillus zanthoxyli 40.0% and Proteus vulgaris 20.0%. Utako Mechanic workshops were Enterobacter kobei 20.0%, Pseudomonas synxantha 40.0%, Bacillus zanthoxyli 20.0% and Proteus vulgaris 40.0%. Gwarinpa Mechanic workshops were Pseudomonas synxantha 20.0% and Bacillus zanthoxyli 20.0%. Area one Mechanic workshops were Enterobacter kobei 40.0% and Pseudomonas synxantha 40.0%. The effect of days on utilization of spent hydrocarbon showed that Pseudomonas synxantha had highest utilized of spent hydrocarbon 19.55mg/ml after 21 days. The effect of pH on utilization of spent hydrocarbon show that at pH 7.5, Enterobacter kobei, Bacillus zanthoxyli and Proteus vulgaris species had the highest utilization of spent hydrocarbon ranging from 5 9.33mg/ml-12.70mg/ml. Effect of temperature on utilization of spent hydrocarbon showed that at 28OC Enterobacter kobei, Pseudomonas synxantha, Bacillus zanthxyli and Proteus vulgaris had the highest utilization of spent hydrocarbon ranging from 5.51mg/ml- 11.11mg/ml. the bacteria isolated from the contaminated soil have the ability to utilized the hydrocarbon if the soil is amended with some mineral element as shown in this study. Conclusion: In conclusion bacteria isolates effectively bioremediated the automechanic oil polluted soil with a reduction of hydrocarbon pollutants.

Gian Luigi Garbini, Anna Barra Caracciolo, Paola Grenni

Microorganisms • 2023

Electroactive bacteria (EAB) are natural microorganisms (mainly Bacteria and Archaea) living in various habitats (e.g., water, soil, sediment), including extreme ones, which can interact electrically each other and/or with their extracellular environments. There has been an increased interest in recent years in EAB because they can generate an electrical current in microbial fuel cells (MFCs). MFCs rely on microorganisms able to oxidize organic matter and transfer electrons to an anode. The latter electrons flow, through an external circuit, to a cathode where they react with protons and oxygen. Any source of biodegradable organic matter can be used by EAB for power generation. The plasticity of electroactive bacteria in exploiting different carbon sources makes MFCs a green technology for renewable bioelectricity generation from wastewater rich in organic carbon. This paper reports the most recent applications of this promising technology for water, wastewater, soil, and sediment recovery. The performance of MFCs in terms of electrical measurements (e.g., electric power), the extracellular electron transfer mechanisms by EAB, and MFC studies aimed at heavy metal and organic contaminant bioremediationF are all described and discussed.

Dewu Ding, Xiao Sun

Genes • 2018

Shewanella oneidensis MR-1 can transfer electrons from the intracellular environment to the extracellular space of the cells to reduce the extracellular insoluble electron acceptors (Extracellular Electron Transfer, EET). Benefiting from this EET capability, Shewanella has been widely used in different areas, such as energy production, wastewater treatment, and bioremediation. Genome-wide proteomics data was used to determine the active proteins involved in activating the EET process. We identified 1012 proteins with decreased expression and 811 proteins with increased expression when the EET process changed from inactivation to activation. We then networked these proteins to construct the active protein networks, and identified the top 20 key active proteins by network centralization analysis, including metabolism- and energy-related proteins, signal and transcriptional regulatory proteins, translation-related proteins, and the EET-related proteins. We also constructed the integrated protein interaction and transcriptional regulatory networks for the active proteins, then found three exclusive active network motifs involved in activating the EET process—Bi-feedforward Loop, Regulatory Cascade with a Feedback, and Feedback with a Protein–Protein Interaction (PPI)—and identified the active proteins involved in these motifs. Both enrichment analysis and comparative analysis to the whole-genome data implicated the multiheme c-type cytochromes and multiple signal processing proteins involved in the process. Furthermore, the interactions of these motif-guided active proteins and the involved functional modules were discussed. Collectively, by using network-based methods, this work reported a proteome-wide search for the key active proteins that potentially activate the EET process.

Peilu Xie, Yuanyou Xu, Jiaxin Tang et al.

Communications Biology • 2024

AbstractSiderophore-dependent iron uptake is a mechanism by which microorganisms scavenge and utilize iron for their survival, growth, and many specialized activities, such as pathogenicity. The siderophore biosynthetic system PubABC in Shewanella can synthesize a series of distinct siderophores, yet how it is regulated in response to iron availability remains largely unexplored. Here, by whole genome screening we identify TCS components histidine kinase (HK) BarA and response regulator (RR) SsoR as positive regulators of siderophore biosynthesis. While BarA partners with UvrY to mediate expression of pubABC post-transcriptionally via the Csr regulatory cascade, SsoR is an atypical orphan RR of the OmpR/PhoB subfamily that activates transcription in a phosphorylation-independent manner. By combining structural analysis and molecular dynamics simulations, we observe conformational changes in OmpR/PhoB-like RRs that illustrate the impact of phosphorylation on dynamic properties, and that SsoR is locked in the ‘phosphorylated’ state found in phosphorylation-dependent counterparts of the same subfamily. Furthermore, we show that iron homeostasis global regulator Fur, in addition to mediating transcription of its own regulon, acts as the sensor of iron starvation to increase SsoR production when needed. Overall, this study delineates an intricate, multi-tiered transcriptional and post-transcriptional regulatory network that governs siderophore biosynthesis.

Aisha Awad Alshahrani

ECS Meeting Abstracts • 2018

The goal of this study is understanding phenomena which may help design electrode modifications enhancing efficiency of microbial fuel cells. Our hypothesis is that the rate of deposition is proportional to both composition of the outer cell membrane and the bulk concentration. We also suggest that ionic strength and ion identity can affect the efficiency of sticking after initial encounter. Shown here are electrochemical studies on effect of salt concentration on S. oneidensis MR-1 attachment and growth at ITO electrodes. Initial surface coverage of bacteria can be measured with respect to four metric. One metric is the observed lag time before currents increase during bacterial loading at the ITO surface. A second one is the current associated with that lag time. The third is the maximum anodic current that occurs after the lag period. Finally a cyclic voltammetric experiment following loading has a metric associated with the cathodic peak current. The peak current is very large for NaCl compare to CsCl. The final coverage (as measured by cathodic peak current in cyclic voltammetry, ipc) increases with increasing ionic strength (IS). We suggest that the behavior of cathodic peak current is very sensitive to the salt concentrations and bacteria harvest time. Our results clearly show a major difference in attachment and behavior of S. oneidensis MR-1 for NaCl compared to CsCl. CsCl inhibits all four metrics associated with loading at +0.2 vs Ag/AgCl (lag time, lag current, maximum loading current and cyclic voltammetric peak current).

Kenneth L. Brockman, Sheetal Shirodkar, Trevor J. Croft et al.

Scientific Reports • 2020

AbstractShewanella oneidensis, a metal reducer and facultative anaerobe, expresses a large number of c-type cytochromes, many of which function as anaerobic reductases. All of these proteins contain the typical heme-binding motif CXXCH and require the Ccm proteins for maturation. Two c-type cytochrome reductases also possess atypical heme-binding sites, the NrfA nitrite reductase (CXXCK) and the SirA sulfite reductase (CX12NKGCH). S. oneidensis MR-1 encodes two cytochrome c synthetases (CcmF and SirE) and two apocytochrome c chaperones (CcmI and SirG). SirE located in the sir gene cluster is required for the maturation of SirA, but not NrfA. Here we show that maturation of SirA requires the combined function of the two apocytochrome c chaperones CcmI and SirG. Loss of either protein resulted in decreased sulfite reductase. Furthermore, SirA was not detected in a mutant that lacked both chaperones, perhaps due to misfolding or instability. These results suggest that CcmI interacts with SirEFG during SirA maturation, and with CcmF during maturation of NrfA. Additionally, we show that CRP regulates expression of sirA via the newly identified transcriptional regulatory protein, SirR.

A. A. Samkov, Yu. A. Chugunova, M. N. Kruglova et al.

Прикладная биохимия и микробиология • 2023

The effect of the polarity of the electrical stimulation of the external circuit of the bioelectrochemical systems, as well as the immobilization of Shewanella oneidensis MR-1 cells containing the DyP peroxidase gene on the rate of discoloration of dyes of different types was found. For the crystal violet triphenylmethane dye, the maximum decolorization rate by suspended S. oneidensis MR-1 cells 2.05 ± 0.07 μM/h was noted in the case of connecting a 1.2 V direct polarity DC voltage source. One of the minimum rates was observed in the case of reverse polarity of the connection. In the case of cells immobilized on the anode, the rate was higher, reaching 2.91 ± 0.09 μM/h and did not decrease with increasing substrate concentration. The lowest values were also noted for the reverse connection of the voltage source. In case of the azo dye congo red, the maximum rate was found for a source with direct connection and an open circuit (0.26 ± 0.01 and 0.29 ± ± 0.02 μM/h, respectively), the minimum value is 0.11 ± 0.02 μM/h for reverse connection. For the crystal violet decolorization products, a significant decrease in the intensity of the main absorption peak at 590 nm band was found, with no notable hypsochromic shift. The qualitative changes in the decolorization products composition are indicated by the appearance, in case of a direct polarity of the ionistor connection, of a new absorption maximum in the region of 360 nm. The results may be of interest for the development of new methods of bioelectrochemical cleaning.

Reem Alshehri, Alanah Fitch

ECS Meeting Abstracts • 2020

The role of structural iron in clays to enhance the electron transfer of Shewanella Oneidensis MR-1 was investigated. Three types of clays containing different amounts of iron situated in the octahedral sites have been used to modify the ITO electrodes: nontronite NAu-1, montmorillonite (Wyoming) SWy-1, and synthetic montmorillonite SYn-1. The interaction between bacterial cells and the clay, which modified the ITO electrodes were studied by potential step, cyclic voltammetry, confocal microscope, and scanning electron microscope SEM. Experimental results showed that the current density generated using iron containing clays NAu-1 and SWy-1 to modify the ITO electrode was 19 and 3 times higher than that produced using the bare ITO electrode. Mechanism of electrochemical production deviated for the iron containing clay NAu-1 Keywords Shewanella Oneidensis MR-1, Clay, Modified ITO electrode, MFC

Shuai Xu, Mohamed El-Naggar

ECS Meeting Abstracts • 2018

Shewanella oneidensis MR-1 can gain energy by performing extracellular electron transport (EET) to external insoluble electron acceptors ranging from natural minerals to synthetic electrode surfaces when poised at proper potentials. Outer membrane c-type multi-heme cytochromes play a critical role in mediating this electron transport. The abundance of these cytochromes on the cell surface has also been hypothesized to facilitate long-distance electron transport along multicellular biofilms, in a manner similar to redox active polymers containing discrete redox moieties. Here we report measurements of electron transport in living S. oneidensis biofilms that bridged interdigitated array (IDA) microelectrodes. Electrochemical gating reveals a peak in the conduction current at the expected formal potential of the cytochrome conduits, consistent with redox conductivity where transport is driven by a multistep electron hopping mechanism through the heme network. The temperature dependency of the biofilm conduction is also consistent with such a thermally activated process, where conductivity increases with increasing temperature. In addition, the measured activation energy (0.315 eV) is consistent with the computationally-determined activation energy of the S. oneidensis Mtr decaheme cytochromes.