DOCSLIB.ORG

Microbial Electroactive Biofilms Dominated by Geoalkalibacter Spp

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Microbial Electroactive Biofilms Dominated by Geoalkalibacter Spp www.nature.com/npjbiofilms ARTICLE OPEN Microbial electroactive biofilms dominated by Geoalkalibacter spp. from a highly saline–alkaline environment ✉ Sukrampal Yadav 1 and Sunil A. Patil 1 Understanding of the extreme microorganisms that possess extracellular electron transfer (EET) capabilities is pivotal to advance electromicrobiology discipline and to develop niche-specific microbial electrochemistry-driven biotechnologies. Here, we report on the microbial electroactive biofilms (EABs) possessing the outward EET capabilities from a haloalkaline environment of the Lonar lake. We used the electrochemical cultivation approach to enrich haloalkaliphilic EABs under 9.5 pH and 20 g/L salinity conditions. The electrodes controlled at 0.2 V vs. Ag/AgCl yielded the best-performing biofilms in terms of maximum bioelectrocatalytic current densities of 548 ± 23 and 437 ± 17 µA/cm2 with acetate and lactate substrates, respectively. Electrochemical characterization of biofilms revealed the presence of two putative redox-active moieties with the mean formal potentials of 0.183 and 0.333 V vs. Ag/ AgCl, which represent the highest values reported to date for the EABs. 16S-rRNA amplicon sequencing of EABs revealed the dominance of unknown Geoalkalibacter sp. at ~80% abundance. Further investigations on the haloalkaliphilic EABs possessing EET components with high formal potentials might offer interesting research prospects in electromicrobiology. npj Biofilms and Microbiomes (2020) 6:38 ; https://doi.org/10.1038/s41522-020-00147-7 1234567890():,; INTRODUCTION electroactivity include harvesting energy (e.g., electricity or Electromicrobiology is a new subdiscipline of (environmental) hydrogen) from waste streams with extreme characteristics, microbiology, which deals with the study of electrochemical developing energy-efficient bioproduction processes, and bior- interactions or extracellular electron transfer (EET) processes emediation of specific pollutants in extreme environments. between microorganisms and the solid-state electron acceptors Researchers have explored mostly normal habitats for the EAMs 4,13 or donors, and their implications in different environments1,2. The so far . The extreme environments remain poorly studied for microorganisms which use EET to achieve their respiratory or such microorganisms, mainly due to difficulties in sampling and metabolic processes are referred to as electroactive microorgan- conducting in situ experiments, as well as lack of appropriate 2,14 isms (EAMs)3,4. These are further subcategorized into exoelectro- enrichment protocols . A few pure culture isolates of the gens and electrotrophs. Exoelectrogens use outward EET to extreme EAMs are known or available4,15,16. Very few studies have reduce the extracellular solid-state electron acceptors, such as reported on the diversity of EAMs from extreme environments. – mineral oxides and electrodes, and achieve their respiration. In These include, for instance, highly saline17 19, extreme acidic20 and contrast, electrotrophs use inward EET to oxidize the solid-state alkaline21, extreme low22 and high temperature19,23, high tem- electron donor sources, in order to maintain their respiratory and perature and pressure24,25, and deep subsurface26 habitats. A metabolic activities. These microorganisms play important roles in combination of some of these extreme conditions also exists in different biogeochemical processes, such as mineral recycling5–7 some environments. Examples include saline-alkaline or haloalka- and interspecies electron transfer8,9, and are used for the line, high temperature–low pH, and extreme saline–high tem- development of various applications ranging from wastewater perature environments that host those microbes, which are treatment and concomitant water reclamation and energy adapted to two different extreme conditions. Exploring such production10,11, bioproduction to bioremediation, and habitats is expected to unravel the unknown microbial diversity biosensing1,12. and metabolic traits that could broaden the understanding of Strengthening of the foundation of electromicrobiology as a different ecological niches for EAMs and may offer opportunities major discipline in microbiology requires a broader and improved for their use under specialized extreme conditions. understanding of EAMs and their EET mechanisms from different The electroactivity of a few microorganisms that can grow environments. In particular, understanding the diversity of under highly saline or alkaline or haloalkaline conditions has been extreme EAMs with different metabolic capabilities holds great studied with the pure culture isolates of Geoalkalibacter ferrihy- potential not only to unravel their ecological significance, but also driticus, Geoalkalibacter subterraneus, and Natrialba magadii to the future development of niche-specific microbial available in the culture repositories13,17,21,27,28. The adaptation electrochemistry-driven biotechnological applications. For and enrichment of the mixed microbial community to develop instance, the use of extreme EAMs is desired to overcome the tolerance to free ammonia under highly saline and alkaline limitations associated with sluggish reaction kinetics and electron conditions has also been reported29. However, the real haloalka- transfer, poor electrolyte conductivity and associated ohmic line habitats have barely been explored for the EAMs. For instance, losses, and low organics removal efficiencies in bioelectrochemical Kumar et al. enriched a mixed microbial community capable of systems operated at normal conditions. Some of the promising producing bioelectrocatalytic current generation from the applications for microorganisms possessing extreme haloalkaline sediments of Texcoco Lake, Mexico, but did not 1Department of Earth and Environmental Sciences, Indian Institute of Science Education and Research Mohali (IISER Mohali), Knowledge City, Sector 81, SAS Nagar, Punjab ✉ 140306, India. email: [email protected] Published in partnership with Nanyang Technological University S. Yadav and S.A. Patil 2 analyze the electroactive community30. To the best of our Electrochemical enrichment or cultivation of the electroactive knowledge, no study has been conducted on a detailed under- microorganisms standing of the diversity of EAMs from the haloalkaline habitat EAMs can grow by linking substrate oxidation reaction to the thus far. reduction of the solid-state electrode in the absence of any other In this study, we present the electrochemical enrichment and electron acceptor. In such cases, microbial substrate oxidation is characterization of the exoelectrogenic microorganisms from the directly related to the bioelectrocatalytic current generation, extreme haloalkaline environment of Lonar Lake. It is the only which can be monitored by the chronoamperometry (CA) haloalkaline hypervelocity impact meteorite Crater Lake formed in technique38. Figure 1 shows the CA profiles, i.e., bioelectrocatalytic basaltic rock in the world (Supplementary Fig. 1). It is known for its current generation by microorganisms at the electrodes polarized high saline (ranging between 5 and 24 g/L) and alkaline at 0.0, 0.2, and 0.4 V. The reactors with working electrodes (9.5–10 pH) environment31,32. The variation in the salinity data in polarized at 0.2 V showed current production within 2 days of the literature is due to variations in the sampling locations and inoculation (Fig. 1c, d), and achieved the maximum current seasons. It has been the hotspot for geochemists, astrobiologists, densities of 548 ± 23 and 437 ± 17 µA/cm2 with acetate and ecologists, and microbiologists due to its unique characteristics. lactate substrates, respectively. In the case of 0 and 0.4 V The lake system has been well explored for the isolation of conditions, the start-up time of noticeable current production was >7 days. Moreover, low current densities of 117 ± 6 and 135 ± different microbial strains and to understand the broad microbial 2 2 diversity33–35, but not for the EAMs. For studying the electro- 12 µA/cm at 0 V (Fig. 1a, b), and 155 ± 31 and 238 ± 26 µA/cm at microbiology of this lake, we used the electrochemical enrichment 0.4 V (Fig. 1e, f) were achieved with acetate and lactate, respectively, by the enriched microorganisms compared to 0.2 V or cultivation approach. It involves the use of polarized electrodes − at different potentials as an analog or proxy to different natural condition. The electrodes polarized at 0.2 V showed no or negligible bioelectrocatalytic current response (Supplementary terminal electron acceptor conditions essential to the microbial Fig. 2). It is most likely due to a very little difference between the respiratory activities. It was followed by the detailed characteriza- reduction potential of the electron donor (i.e., acetate or lactate) tion of the best-performing enriched haloalkaliphilic microbial and the potential that was applied at the electrode, which acted EABs via electrochemical, microscopic, and 16S-rRNA amplicon as the electron acceptor. Similarly, both controls, namely abiotic sequencing techniques. connected and biotic unconnected, exhibited no substrate oxidation and current response (Supplementary Fig. 3). Hence, 1234567890():,; RESULTS the electric current production in all other experimental condi- tions can be attributed to the bioelectrocatalytic activity of the Sediment characteristics enriched haloalkaliphilic microorganisms. The sediment samples obtained during winter and monsoon The low bioelectrocatalytic
Load more

Recommended publications
  • Table 1. Overview of Reactions Examined in This Study. ΔG Values Were Obtained from Thauer Et Al., 1977
    Supplemental Information: Table 1. Overview of reactions examined in this study. ΔG values were obtained from Thauer et al., 1977. No. Equation ∆G°' (kJ/reaction)* Acetogenic reactions – – – + 1 Propionate + 3 H2O → Acetate + HCO3 + 3 H2 + H +76.1 Sulfate-reducing reactions – 2– – – – + 2 Propionate + 0.75 SO4 → Acetate + 0.75 HS + HCO3 + 0.25 H –37.8 2– + – 3 4 H2 + SO4 + H → HS + 4 H2O –151.9 – 2– – – 4 Acetate + SO4 → 2 HCO3 + HS –47.6 Methanogenic reactions – – + 5 4 H2 + HCO3 + H → CH4 + 3 H2O –135.6 – – 6 Acetate + H2O → CH4 + HCO3 –31.0 Syntrophic propionate conversion – – – + 1+5 Propionate + 0.75 H2O → Acetate + 0.75 CH4 + 0.25 HCO3 + 0.25 H –25.6 Complete propionate conversion by SRB – 2– – – + 2+4 Propionate + 1.75 SO4 → 1.75 HS + 3 HCO3 + 0.25 H –85.4 Complete propionate conversion by syntrophs and methanogens 1+5+6 Propionate– + 1.75 H O → 1.75 CH + 1.25 HCO – + 0.25 H+ –56.6 2 4 3 1 Table S2. Overview of all enrichment slurries fed with propionate and the total amounts of the reactants consumed and products formed during the enrichment period. The enrichment slurries consisted of sediment from either the sulfate zone (SZ), sulfate-methane transition zone (SMTZ) or methane zone (MZ) and were incubated at 25°C or 10°C, with 3 mM, 20 mM or without (-) sulfate amendments along the study. The slurries P1/P2, P3/P4, P5/P6, P7/P8 from each sediment zone are biological replicates. Slurries with * are presented in the propionate conversion graphs and used for molecular analysis.
    [Show full text]
  • Design, Analysis and Application of Synthetic Microbial Consortia Xiaoqiang Jia, Chang Liu, Hao Song, Mingzhu Ding, Jin Du, Qian Ma, Yingjin Yuan *
    ARTICLE IN PRESS Synthetic and Systems Biotechnology ■■ (2016) ■■–■■ Contents lists available at ScienceDirect Synthetic and Systems Biotechnology journal homepage: keaipublishing.com/synbio Design, analysis and application of synthetic microbial consortia Xiaoqiang Jia, Chang Liu, Hao Song, Mingzhu Ding, Jin Du, Qian Ma, Yingjin Yuan * Key Laboratory of Systems Bioengineering, Ministry of Education, School of Chemical Engineering and Technology, Collaborative Innovation Centre of Chemical Science and Engineering (Tianjin), Tianjin University, Tianjin 300072, China ARTICLE INFO ABSTRACT Article history: The rapid development of synthetic biology has conferred almost perfect modification on single cells, Received 17 May 2015 and provided methodological support for synthesizing microbial consortia, which have a much wider Received in revised form 28 January 2016 application potential than synthetic single cells. Co-cultivating multiple cell populations with rational Accepted 12 February 2016 strategies based on interacting relationships within natural microbial consortia provides theoretical as Available online well as experimental support for the successful obtaining of synthetic microbial consortia, promoting it into extensive research on both industrial applications in plenty of areas and also better understanding Keywords: of natural microbial consortia. According to their composition complexity, synthetic microbial consor- Synthetic microbial consortium Single/two/multiple species tia are summarized in three aspects in this review and are discussed in principles of design and construction, insights and methods for analysis, and applications in energy, healthcare, etc. © 2016 Authors. Production and hosting by Elsevier B.V. on behalf of KeAi Communications Co., Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by- nc-nd/4.0/).
    [Show full text]
  • Microbial Fe(III) Oxide Reduction Potential in Chocolate Pots Hot Spring, Yellowstone National Park N
    Geobiology (2016), 14, 255–275 DOI: 10.1111/gbi.12173 Microbial Fe(III) oxide reduction potential in Chocolate Pots hot spring, Yellowstone National Park N. W. FORTNEY,1 S. HE,1 B. J. CONVERSE,1 B. L. BEARD,1 C. M. JOHNSON,1 E. S. BOYD2 ANDE.E.RODEN1 1Department of Geoscience, NASA Astrobiology Institute, University of Wisconsin-Madison, Madison, WI, USA 2Department of Microbiology and Immunology, NASA Astrobiology Institute, Montana State University, Bozeman, MT, USA ABSTRACT Chocolate Pots hot springs (CP) is a unique, circumneutral pH, iron-rich, geothermal feature in Yellowstone National Park. Prior research at CP has focused on photosynthetically driven Fe(II) oxidation as a model for mineralization of microbial mats and deposition of Archean banded iron formations. However, geochemical and stable Fe isotopic data have suggested that dissimilatory microbial iron reduction (DIR) may be active within CP deposits. In this study, the potential for microbial reduction of native CP Fe(III) oxides was inves- tigated, using a combination of cultivation dependent and independent approaches, to assess the potential involvement of DIR in Fe redox cycling and associated stable Fe isotope fractionation in the CP hot springs. Endogenous microbial communities were able to reduce native CP Fe(III) oxides, as documented by most probable number enumerations and enrichment culture studies. Enrichment cultures demonstrated sus- tained DIR driven by oxidation of acetate, lactate, and H2. Inhibitor studies and molecular analyses indicate that sulfate reduction did not contribute to observed rates of DIR in the enrichment cultures through abi- otic reaction pathways. Enrichment cultures produced isotopically light Fe(II) during DIR relative to the bulk solid-phase Fe(III) oxides.
    [Show full text]
  • Supplementary Information for Microbial Electrochemical Systems Outperform Fixed-Bed Biofilters for Cleaning-Up Urban Wastewater
    Electronic Supplementary Material (ESI) for Environmental Science: Water Research & Technology. This journal is © The Royal Society of Chemistry 2016 Supplementary information for Microbial Electrochemical Systems outperform fixed-bed biofilters for cleaning-up urban wastewater AUTHORS: Arantxa Aguirre-Sierraa, Tristano Bacchetti De Gregorisb, Antonio Berná, Juan José Salasc, Carlos Aragónc, Abraham Esteve-Núñezab* Fig.1S Total nitrogen (A), ammonia (B) and nitrate (C) influent and effluent average values of the coke and the gravel biofilters. Error bars represent 95% confidence interval. Fig. 2S Influent and effluent COD (A) and BOD5 (B) average values of the hybrid biofilter and the hybrid polarized biofilter. Error bars represent 95% confidence interval. Fig. 3S Redox potential measured in the coke and the gravel biofilters Fig. 4S Rarefaction curves calculated for each sample based on the OTU computations. Fig. 5S Correspondence analysis biplot of classes’ distribution from pyrosequencing analysis. Fig. 6S. Relative abundance of classes of the category ‘other’ at class level. Table 1S Influent pre-treated wastewater and effluents characteristics. Averages ± SD HRT (d) 4.0 3.4 1.7 0.8 0.5 Influent COD (mg L-1) 246 ± 114 330 ± 107 457 ± 92 318 ± 143 393 ± 101 -1 BOD5 (mg L ) 136 ± 86 235 ± 36 268 ± 81 176 ± 127 213 ± 112 TN (mg L-1) 45.0 ± 17.4 60.6 ± 7.5 57.7 ± 3.9 43.7 ± 16.5 54.8 ± 10.1 -1 NH4-N (mg L ) 32.7 ± 18.7 51.6 ± 6.5 49.0 ± 2.3 36.6 ± 15.9 47.0 ± 8.8 -1 NO3-N (mg L ) 2.3 ± 3.6 1.0 ± 1.6 0.8 ± 0.6 1.5 ± 2.0 0.9 ± 0.6 TP (mg
    [Show full text]
  • Effect of Temperature on a Miniaturized Microbial Fuel Cell (MFC) Hao Ren*, Chenming Jiang and Junseok Chae
    Ren et al. Micro and Nano Syst Lett (2017) 5:13 DOI 10.1186/s40486-017-0048-8 LETTER Open Access Effect of temperature on a miniaturized microbial fuel cell (MFC) Hao Ren*, Chenming Jiang and Junseok Chae Abstract A microbial fuel cell (MFC) is a bioinspired energy converter which directly converts biomass into electricity through the catalytic activity of a specific species of bacteria. The effect of temperature on a miniaturized microbial fuel cell with Geobacter sulfurreducens dominated mixed inoculum is investigated in this paper for the first time. The miniatur- ized MFC warrants investigation due to its small thermal mass, and a customized setup is built for the temperature effect characterization. The experiment demonstrates that the optimal temperature for the miniaturized MFC is 322–326 K (49–53 °C). When the temperature is increased from 294 to 322 K, a remarkable current density improve- 2 ment of 282% is observed, from 2.2 to 6.2 Am− . Furthermore, we perform in depth analysis on the effect of tempera- ture on the miniaturized MFC, and found that the activation energy for the current limiting mechanism of the MFC is approximately between 0.132 and 0.146 eV, and the result suggest that the electron transfer between cytochrome c is the limiting process for the miniaturized MFC. Keywords: Microbial fuel cell (MFC), Micro-electro-mechanical systems (MEMS), Temperature effect, Activation energy, Extracellular electron transfer (EET), Cytochrome c, Rate limiting step Background and power density than other types of exoelectrogen. The A microbial fuel cell electrochemically converts bio- effect of temperature on microbial fuel cells with Geo- mass into electricity through the catalytic activity of bacter as exoelectrogen has been investigated by many specific species of bacteria, named exoelectrogen or researchers, and it is reported that the optimal temper- anode-respiring bacteria, which are capable of transfer ature to be 298–303 K (25–30 °C) for macro/mesoscale electrons outside their outer membrane [1–3].
    [Show full text]
  • Microbial Structure and Energy Generation in Microbial Fuel Cells Powered with Waste Anaerobic Digestate
    energies Article Microbial Structure and Energy Generation in Microbial Fuel Cells Powered with Waste Anaerobic Digestate Dawid Nosek * and Agnieszka Cydzik-Kwiatkowska Department of Environmental Biotechnology, University of Warmia and Mazury in Olsztyn, Słoneczna 45 G, 10-709 Olsztyn, Poland; [email protected] * Correspondence: [email protected]; Tel.: +48-89-523-4144; Fax: +48-89-523-4131 Received: 19 July 2020; Accepted: 7 September 2020; Published: 10 September 2020 Abstract: Development of economical and environment-friendly Microbial Fuel Cells (MFCs) technology should be associated with waste management. However, current knowledge regarding microbiological bases of electricity production from complex waste substrates is insufficient. In the following study, microbial composition and electricity generation were investigated in MFCs powered with waste volatile fatty acids (VFAs) from anaerobic digestion of primary sludge. Two anode sizes were tested, resulting in organic loading rates (OLRs) of 69.12 and 36.21 mg chemical oxygen demand (COD)/(g MLSS d) in MFC1 and MFC2, respectively. Time of MFC operation affected the microbial · structure and the use of waste VFAs promoted microbial diversity. High abundance of Deftia sp. and Methanobacterium sp. characterized start-up period in MFCs. During stable operation, higher OLR in MFC1 favored growth of exoelectrogens from Rhodopseudomonas sp. (13.2%) resulting in a higher and more stable electricity production in comparison with MFC2. At a lower OLR in MFC2, the percentage of exoelectrogens in biomass decreased, while the abundance of genera Leucobacter, Frigoribacterium and Phenylobacterium increased. In turn, this efficiently decomposed complex organic substances, favoring high and stable COD removal (over 85%).
    [Show full text]
  • Biofilm Engineering Approaches for Improving the Performance Of
    REVIEW published: 05 July 2018 doi: 10.3389/fenrg.2018.00063 Biofilm Engineering Approaches for Improving the Performance of Microbial Fuel Cells and Bioelectrochemical Systems Maria Joseph Angelaalincy 1, Rathinam Navanietha Krishnaraj 2, Ganeshan Shakambari 1, Balasubramaniem Ashokkumar 3, Shanmugam Kathiresan 4 and Perumal Varalakshmi 1* 1 Department of Molecular Microbiology, School of Biotechnology, Madurai Kamaraj University, Madurai, India, 2 Department of Chemical and Biological Engineering, Composite and Nanocomposite Advanced Manufacturing – Biomaterials Center, Rapid City, SD, United States, 3 Department of Genetic Engineering, School of Biotechnology, Madurai Kamaraj University, Madurai, India, 4 Department of Molecular Biology, School of Biological Sciences, Madurai Kamaraj University, Madurai, India Microbial fuel cells (MFCs) are emerging as a promising future technology for a wide range Edited by: Abudukeremu Kadier, of applications in addition to sustainable electricity generation. Electroactive (EA) biofilms National University of Malaysia, produced by microorganisms are the key players in the bioelectrochemical systems Malaysia involving microorganism mediated electrocatalytic reactions. Therefore, genetically Reviewed by: modifying the organism for increased production of EA biofilms and improving the extra G. Velvizhi, Indian Institute of Chemical electron transfer (EET) mechanisms may attribute to increase in current density of a MFC Technology (CSIR), India and an increased COD removal in wastewater treatment plant coupled MFC systems. Özlem Onay, Anadolu University, Turkey Extracellular polysaccharides (EPS) produced by the organisms attribute to both biofilm *Correspondence: formation and electron transfer. Although cell surface modification, media optimization Perumal Varalakshmi and operation parameters validation are established as enhancement strategies for a fuel [email protected] cell performance, engineering the vital genes involved in electroactive biofilm formation Specialty section: is the future hope.
    [Show full text]
  • Geobacter Strains Expressing Poorly Conductive Pili Reveal
    University of Massachusetts Amherst ScholarWorks@UMass Amherst Microbiology Department Faculty Publication Microbiology Series 2018 Geobacter Strains Expressing Poorly Conductive Pili Reveal Constraints on Direct Interspecies Electron Transfer Mechanisms Toshiyuki Ueki University of Massachusetts Amherst Kelly P. Nevin University of Massachusetts Amherst Amelia-Elena Rotaru University of Southern Denmark Li-Ying Wang University of Massachusetts Amherst Joy E. Ward University of Massachusetts Amherst See next page for additional authors Follow this and additional works at: https://scholarworks.umass.edu/micro_faculty_pubs Recommended Citation Ueki, Toshiyuki; Nevin, Kelly P.; Rotaru, Amelia-Elena; Wang, Li-Ying; Ward, Joy E.; Woodard, Trevor L.; and Lovley, Derek R., "Geobacter Strains Expressing Poorly Conductive Pili Reveal Constraints on Direct Interspecies Electron Transfer Mechanisms" (2018). mBio. 319. http://dx.doi.org/10.1128/mBio.01273-18 This Article is brought to you for free and open access by the Microbiology at ScholarWorks@UMass Amherst. It has been accepted for inclusion in Microbiology Department Faculty Publication Series by an authorized administrator of ScholarWorks@UMass Amherst. For more information, please contact [email protected]. Authors Toshiyuki Ueki, Kelly P. Nevin, Amelia-Elena Rotaru, Li-Ying Wang, Joy E. Ward, Trevor L. Woodard, and Derek R. Lovley This article is available at ScholarWorks@UMass Amherst: https://scholarworks.umass.edu/micro_faculty_pubs/319 RESEARCH ARTICLE crossm Geobacter Strains
    [Show full text]
  • Effect of Electrode Spacing on Electron Transfer and Conductivity of Geobacter Sulfurreducens Biofilms
    Bioelectrochemistry 131 (2020) 107395 Contents lists available at ScienceDirect Bioelectrochemistry journal homepage: www.elsevier.com/locate/bioelechem Effect of electrode spacing on electron transfer and conductivity of Geobacter sulfurreducens biofilms Panpan Liu a,b, Abdelrhman Mohamed b,PengLianga, Haluk Beyenal b,⁎ a State Key Joint Laboratory of Environment Simulation and Pollution Control School of Environment, Tsinghua University, Beijing 100084, PR China b The Gene and Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman, WA 99163, USA article info abstract Article history: To understand electron transport in electrochemically active biofilms, it is necessary to elucidate the heteroge- Received 15 April 2019 neous electron transport across the biofilm/electrode interface and in the interior of G. sulfurreducens biofilms Received in revised form 12 September 2019 bridging gaps of varying widths. The conductivity of Geobacter sulfurreducens biofilm bridging nonconductive Accepted 13 September 2019 gaps with widths of 5 µm, 10 µm, 20 µm and 50 µm is investigated. Results of electrochemical gating measure- Available online 4 October 2019 ment show that biofilm conductivity peaks at the potential of −0.35 V vs. Ag/AgCl. The biofilm conductivity in- creases with gap width (10.4 ± 0.2 µS cm−1 in 5 µm gap, 13.3 ± 0.2 µS cm−1 in 10 µm gap, 16.7 ± 1.4 µS cm−1 in Keywords: −1 Electrochemically active biofilm 20 µm gap and 41.8 ± 2.02 µS cm in 50 µm gap). These results revealed that electron transfer in Exoelectrogens G. sulfurreducens biofilm is a redox-driven. In addition, higher biofilm conductivities and lower charge transfer Biofilm conductivity resistances are observed in all gaps under a turnover condition than in those under a non-turnover condition.
    [Show full text]
  • Carbon Fiber Electrode As an Electron Acceptor for a Microbial Fuel Cell Using Geobacter
    Cantaurus, Vol. 15, 24-26, May 2007 © McPherson College Division of Science and Technology Carbon Fiber Electrode as an Electron Acceptor for a Microbial Fuel Cell Using Geobacter Alicia R Schoen ABSTRACT Microbial fuel cells use bacteria to produce electricity. A dual-chambered microbial fuel cell was used to harness electricity from Geobacter, with carbon fiber as the electrode. The peak current measured was 10.7 mA on the first day, and fell to zero within 5 days. This result is comparable to a similar experiment using the carbon fiber electrode with a different bacteria, but less than typical results from Geobacter when different electrodes were used. Keywords: microbial fuel cell, Geobacter INTRODUCTION Microbial fuel cells (MFCs) are devices that use Scanning electron microscope images show bacteria as the catalysts to oxidize organic and Geobacter growing directly on the surface of a inorganic matter and generate current. Electrons graphite electrode and nearly covering it. This would produced by the bacteria from these substrates are suggest the electrode’s utility as an electron acceptor transferred to the anode (negative terminal) and flow in the bacteria’s metabolic cycle. Other organisms to the cathode (positive terminal) linked by a have shown the ability to transfer electrons, but conductive material containing a resistor, or operated Geobacter has thus far produced the highest current. under a load (i.e., producing electricity that runs a It has recently been discovered that Geobacter is device) (Logan 2006). able to perform this mediator-less transfer with the The proposed uses of MFCs are many. Min and use of nanowires.
    [Show full text]
  • Bacterial Community Structure in a Sympagic Habitat Expanding with Global Warming: Brackish Ice Brine at 85€“90 °N
    The ISME Journal (2019) 13:316–333 https://doi.org/10.1038/s41396-018-0268-9 ARTICLE Bacterial community structure in a sympagic habitat expanding with global warming: brackish ice brine at 85–90 °N 1,11 1,2 3 4 5,8 Beatriz Fernández-Gómez ● Beatriz Díez ● Martin F. Polz ● José Ignacio Arroyo ● Fernando D. Alfaro ● 1 1 2,6 5 4,7 Germán Marchandon ● Cynthia Sanhueza ● Laura Farías ● Nicole Trefault ● Pablo A. Marquet ● 8,9 10 10 Marco A. Molina-Montenegro ● Peter Sylvander ● Pauline Snoeijs-Leijonmalm Received: 12 February 2018 / Revised: 11 June 2018 / Accepted: 24 July 2018 / Published online: 18 September 2018 © International Society for Microbial Ecology 2018 Abstract Larger volumes of sea ice have been thawing in the Central Arctic Ocean (CAO) during the last decades than during the past 800,000 years. Brackish brine (fed by meltwater inside the ice) is an expanding sympagic habitat in summer all over the CAO. We report for the first time the structure of bacterial communities in this brine. They are composed of psychrophilic extremophiles, many of them related to phylotypes known from Arctic and Antarctic regions. Community structure displayed strong habitat segregation between brackish ice brine (IB; salinity 2.4–9.6) and immediate sub-ice seawater (SW; – 1234567890();,: 1234567890();,: salinity 33.3 34.9), expressed at all taxonomic levels (class to genus), by dominant phylotypes as well as by the rare biosphere, and with specialists dominating IB and generalists SW. The dominant phylotypes in IB were related to Candidatus Aquiluna and Flavobacterium, those in SW to Balneatrix and ZD0405, and those shared between the habitats to Halomonas, Polaribacter and Shewanella.
    [Show full text]
  • Electron Transfer Through the Outer Membrane of Geobacter Sulfurreducens a DISSERTATION SUBMITTED to the FACULTY of the UNIVE
    Electron transfer through the outer membrane of Geobacter sulfurreducens A DISSERTATION SUBMITTED TO THE FACULTY OF THE UNIVERSITY OF MINNESOTA BY Fernanda Jiménez Otero IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR IN PHILOSOPHY Dr. Daniel R. Bond May, 2018 Fernanda Jiménez Otero, 2018, © Acknowledgements This dissertation and the degree I have gained with it, would not have been possible without the help and support from an invaluable group of people. The training I received from Chi Ho Chan and Caleb Levar continues to be essential in the way I approach scientific endeavors. The quality of genetic studies and rigor in microbiology techniques they taught me is a standard I hope to meet throughout my career. Daniel Bond has been much more than I ever expected from an advisor. I have not only gained scientific knowledge from him, but I will take with me the example of what a great mentor represents. His enthusiasm for science is only rivaled by his commitment to past and present members of his laboratory. I am extremely honored to be able to count myself in that group, and I will do my best to represent him proudly in future endeavors. Throughout these five years, Jeff Gralnick has given me numerous opportunities to explore all aspects of a scientific career. Not only is Chapter 2 a result of his vision, but I feel less intimidated by a career in science as a result of his mentoring and support. The faculty members in my committee- Carrie Wilmot, Brandy Toner, and Larry Wackett, have made sure I am well prepared for i every step through graduate school.
    [Show full text]