key: cord-0261526-7gpyhye9 authors: Katuri, Krishna P.; Kamireddy, Sirisha; Kavanagh, Paul; Mohammad, Ali; Conghaile, Peter Ó; Kumar, Amit; Saikaly, Pascal E.; Leech, Dónal title: Electroactive biofilms on surface functionalized anodes: the anode respiring behavior of a novel electroactive bacterium, Desulfuromonas acetexigens date: 2020-03-05 journal: bioRxiv DOI: 10.1101/2020.03.04.974261 sha: a3dcf4d433ebf28c0f4aaf09d49fa0316c2644f3 doc_id: 261526 cord_uid: 7gpyhye9 Surface chemistry is known to influence the formation, composition and electroactivity of electron-conducting biofilms with however limited information on the variation of microbial composition and electrochemical response during biofilm development to date. Here we present voltammetric, microscopic and microbial community analysis of biofilms formed under fixed applied potential for modified graphite electrodes during early (90 h) and mature (340 h) growth phases. Electrodes modified to introduce hydrophilic groups (−NH2, −COOH and −OH) enhance early-stage biofilm formation compared to unmodified or electrodes modified with hydrophobic groups (−C2H5). In addition, early-stage films formed on hydrophilic electrodes were dominated by the gram-negative sulfur-reducing bacterium Desulfuromonas acetexigens while Geobacter sp. dominated on −C2H5 and unmodified electrodes. As biofilms mature, current generation becomes similar, and D. acetexigens dominates in all biofilms irrespective of surface chemistry. Electrochemistry of pure culture D. acetexigens biofilms reveal that this microbe is capable of forming electroactive biofilms producing considerable current density of > 9 A/m2 in a short period of potential induced growth (~19 h followed by inoculation) using acetate as an electron donor. The inability of D. acetexigens biofilms to use H2 as a sole source electron donor for current generation shows promise for maximizing H2 recovery in single-chambered microbial electrolysis cell systems treating wastewaters. Highlights Anode surface chemistry affects the early stage biofilm formation. Hydrophilic anode surfaces promote rapid start-up of current generation. Certain functionalized anode surfaces enriched the Desulfuromonas acetexigens. D. acetexigens is a novel electroactive bacteria. D. acetexigens biofilms can produce high current density in a short period of potential induced growth D. acetexigens has the ability to maximize the H2 recovery in MEC. TOC – Graphical abstract • Anode surface chemistry affects the early stage biofilm formation. 32 • Hydrophilic anode surfaces promote rapid start-up of current generation. 33 • Certain functionalized anode surfaces enriched the Desulfuromonas acetexigens. 34 • D. acetexigens is a novel electroactive bacteria. 35 • D. acetexigens biofilms can produce high current density in a short period of potential 36 induced growth 37 1. Introduction 81 Microbial electrochemical technologies (METs) are electrochemical devices which utilize 82 microbial biofilms formed at a polarized electrode (anode and/or cathode) to drive 83 electrochemical reaction(s) (Rittmann, 2018 ). An electrochemical potential established at the 84 anode can induce the formation of thick, electron-conducting biofilms composed of special 85 microbial communities known as electroactive bacteria (Schröder et al., 2015) . Such biofilms, 86 predominately composed of anaerobic microbes, respire by utilizing an electrode as a terminal 87 electron acceptor in place of natural oxidants such as iron oxide. Potential electroactive bacteria 88 can be found in diverse environments, ranging from the stratosphere (Zhang et al., 2012) to deep 89 Red Sea brine pools/marine sediments (Shehab et al., 2017) , including sewage (Patil et al., 2010) , 90 sludge, composts, soil, manure, sediments, rumen and agro-industrial wastes ( and G. sulfurreducens) in matured biofilms (53 day aged) developed on a range of functionalized 130 anode surfaces (Guo et al., 2013 terminal groups (Fig. 2B) . There is an increase in the catalytic oxidation current as a function of 304 time after inoculation, despite evidence of uncompensated resistance effect in the CV responses. 305 The sigmoidal shaped CV obtained at 250 h after inoculation (Fig. 2B) , when fit to a simple Ag/AgCl at graphite electrodes. 525 The current generation using formate as electron donor (Fig. 6) 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 Relationship between surface chemistry, biofilm structure, and electron 570 transfer in Shewanella anodes Designing Stable Redox-Active Surfaces: Chemical 572 Attachment of an Osmium Complex to Glassy Carbon Electrodes Prefunctionalized by Electrochemical Reduction of an In Situ-Generated Aryldiazonium Cation Impact of electrode micro-and nano-scale 576 topography on the formation and performance of microbial electrodes Surface Modification for Enhanced Biofilm Formation and Electron 580 Transport in Shewanella Anodes Microbial activity influences electrical conductivity of biofilm anode Electron Transfer from the Living Organism of Shewanella loihica PV-4 Microbial Electrochemical and Fuel Cells Desulfuromonas acetexigens sp. nov., a dissimilatory 590 sulfur-reducing eubacterium from anoxic freshwater sediments On the use of cyclic voltammetry for the study 593 of anodic electron transfer in microbial fuel cells Effects of Surface Charge and Hydrophobicity on Anodic Biofilm Formation Community Composition, and Current Generation in Bioelectrochemical Systems Environmental science & technology 47 Functionally Stable and Phylogenetically Diverse Microbial 601 Enrichments from Microbial Fuel Cells during Wastewater Treatment Microbial population and functional dynamics 605 associated with surface potential and carbon metabolism Charge transport in films of 608 Geobacter sulfurreducens on graphite electrodes as a function of film thickness The role of microbial electrolysis cell in urban 611 wastewater treatment: integration options, challenges, and prospects Dual-Function Electrocatalytic and Macroporous Hollow-Fiber Cathode for Converting 615 Waste Streams to Valuable Resources Using Microbial Electrochemical Systems Geobacter sulfurreducens biofilms 618 developed under different growth conditions on glassy carbon electrodes: insights using 619 cyclic voltammetry Charge Transport 621 through Geobacter sulfurreducens Biofilms Grown on Graphite Rods AnEMBR) with Conductive Hollow-fiber Membrane for Treatment of Low-626 Lowering the applied 628 potential during successive scratching/re-inoculation improves the performance of 629 microbial anodes for microbial fuel cells Sampling location of 631 the inoculum is crucial in designing anodes for microbial fuel cells Is there a Specific Ecological Niche for Electroactive 634 Microorganisms? ChemElectroChem Arylamine 636 functionalization of carbon anodes for improved microbial electrocatalysis Anodes Promote Faster Biofilm Adhesion and Increase Microbial Fuel Cell Performances Improvement of the 642 anodic bioelectrocatalytic activity of mixed culture biofilms by a simple consecutive 643 electrochemical selection procedure Long-term investigation of a novel 645 electrochemical membrane bioreactor for low-strength municipal wastewater treatment Microbial Fuel Cell Membrane Bioreactor with a Conductive Ultrafiltration Membrane 649 Biofilm Voltammetry: Direct Electrochemical Characterization of Catalytic Electrode-653 Enrichment and Analysis of Anode-Respiring Bacteria from Diverse Anaerobic Inocula Anode biofilm transcriptomics reveals outer 659 surface components essential for high density current production in Geobacter 660 sulfurreducens fuel cells Electricity production in biofuel cell 662 using modified graphite electrode with Neutral Red Electroactive mixed culture 665 biofilms in microbial bioelectrochemical systems: The role of temperature for biofilm 666 formation and performance Graphite anode surface 668 modification with controlled reduction of specific aryl diazonium salts for improved 669 microbial fuel cells power output Springer Handbook of Electronic and Photonic Materials Initial development and 673 structure of biofilms on microbial fuel cell anodes Biofilms, active substrata, and me Effect of nitrogen addition on the performance of microbial fuel cell anodes Three-dimensional X-ray microcomputed tomography of 680 carbonates and biofilm on operated cathode in single chamber microbial fuel cell Influence of anode surface chemistry on microbial 684 fuel cell operation Microbial electrochemistry and technology: 686 terminology and classification Application of modified 688 carbon anodes in microbial fuel cells Extracellular electron transfer-dependent 691 anaerobic oxidation of ammonium by anammox bacteria. bioRxiv Enrichment of extremophilic exoelectrogens in microbial electrolysis cells 694 using Red Sea brine pools as inocula Geobacter sp. SD-1 with 696 enhanced electrochemical activity in high-salt concentration solutions Microbial 699 nanowires: an electrifying tale A kinetic perspective on extracellular electron transfer by anode-respiring 702 bacteria Microbial electricity driven anoxic ammonium removal Microfluidic 706 dielectrophoresis illuminates the relationship between microbial cell envelope 707 polarizability and electrochemical activity Endogenous Phenazine Antibiotics Promote 709 Anaerobic Survival of Pseudomonas aeruginosa via Extracellular Electron 710 Enhanced Electricity Production by Use 712 of Reconstituted Artificial Consortia of Estuarine Bacteria Grown as Biofilms Heat map displaying relative abundance of bacterial reads. The genus level (or lowest 194 taxonomic level possible) relative abundance for inoculum and for biofilms sampled from control 195 (unmodified) and functionalized graphite electrodes after early-stage of batch-feed (90 h) and 196 later-stage of continuous feed (340 h) growth conditions. k: kingdom, p: phylum, c: class, o: order 197 and f family Relationship between anode and cell density, and its influence on current 200 production. (B), and correlation between anode surface zeta potential and relative PCA analysis showing 202 relationship between biofilm bacterial communities collected over time (90 h and 340 h) and from 203 different electrode (unmodified and functionalized graphite) surfaces flow feed at a flow rate of 1 L/day, switching to 0.5 L/day at the time indicated by the black 48 arrow. Grey arrow in Figure 1B indicates the time when the biofilms were sampled for SEM and 49 microbial community analysis. Numbers in Figure 1B&C 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 -COOH 22±2 µm A B