51
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Meysman FJR, Cornelissen R, Trashin S, Bonné R, Martinez SH, van der Veen J, Blom CJ, Karman C, Hou JL, Eachambadi RT, Geelhoed JS, Wael KD, Beaumont HJE, Cleuren B, Valcke R, van der Zant HSJ, Boschker HTS, Manca JV. A highly conductive fibre network enables centimetre-scale electron transport in multicellular cable bacteria. Nat Commun 2019; 10:4120. [PMID: 31511526 PMCID: PMC6739318 DOI: 10.1038/s41467-019-12115-7] [Citation(s) in RCA: 65] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2019] [Accepted: 08/19/2019] [Indexed: 11/25/2022] Open
Abstract
Biological electron transport is classically thought to occur over nanometre distances, yet recent studies suggest that electrical currents can run along centimetre-long cable bacteria. The phenomenon remains elusive, however, as currents have not been directly measured, nor have the conductive structures been identified. Here we demonstrate that cable bacteria conduct electrons over centimetre distances via highly conductive fibres embedded in the cell envelope. Direct electrode measurements reveal nanoampere currents in intact filaments up to 10.1 mm long (>2000 adjacent cells). A network of parallel periplasmic fibres displays a high conductivity (up to 79 S cm−1), explaining currents measured through intact filaments. Conductance rapidly declines upon exposure to air, but remains stable under vacuum, demonstrating that charge transfer is electronic rather than ionic. Our finding of a biological structure that efficiently guides electrical currents over long distances greatly expands the paradigm of biological charge transport and could enable new bio-electronic applications. Cable bacteria’ form long multicellular filaments that can transfer electrical currents over centimetre-long distances. Here, Meysman et al. show that the electrical currents run along highly conductive fibres embedded in the cell envelope, and charge transfer is electronic rather than ionic.
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Affiliation(s)
- Filip J R Meysman
- Department of Biology, University of Antwerp, Universiteitsplein 1, B-2610, Wilrijk, Belgium. .,Department of Biotechnology, Delft University of Technology, Van der Maasweg 9, 2629HZ, Delft, The Netherlands.
| | - Rob Cornelissen
- X-LAB, Hasselt University, Agoralaan D, B-3590, Diepenbeek, Belgium
| | - Stanislav Trashin
- AXES Research group, Department of Chemistry, University of Antwerp, Groenenborgerlaan 171, B-2020, Antwerpen, Belgium
| | - Robin Bonné
- X-LAB, Hasselt University, Agoralaan D, B-3590, Diepenbeek, Belgium
| | - Silvia Hidalgo Martinez
- Department of Biology, University of Antwerp, Universiteitsplein 1, B-2610, Wilrijk, Belgium
| | - Jasper van der Veen
- Department of Quantum Nanoscience, Kavli Institute of Nanoscience, Technical University Delft, Lorentzweg 1, 2628 CJ, Delft, The Netherlands
| | - Carsten J Blom
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, van der Maasweg 9, 2629 HZ, Delft, The Netherlands
| | - Cheryl Karman
- Department of Biology, University of Antwerp, Universiteitsplein 1, B-2610, Wilrijk, Belgium.,AXES Research group, Department of Chemistry, University of Antwerp, Groenenborgerlaan 171, B-2020, Antwerpen, Belgium
| | - Ji-Ling Hou
- X-LAB, Hasselt University, Agoralaan D, B-3590, Diepenbeek, Belgium
| | | | - Jeanine S Geelhoed
- Department of Biology, University of Antwerp, Universiteitsplein 1, B-2610, Wilrijk, Belgium
| | - Karolien De Wael
- AXES Research group, Department of Chemistry, University of Antwerp, Groenenborgerlaan 171, B-2020, Antwerpen, Belgium
| | - Hubertus J E Beaumont
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, van der Maasweg 9, 2629 HZ, Delft, The Netherlands
| | - Bart Cleuren
- Theoretical Physics, Hasselt University, Agoralaan D, B-3590, Diepenbeek, Belgium
| | - Roland Valcke
- Molecular and Physical Plant Physiology, Hasselt University, Agoralaan D, B-3590, Diepenbeek, Belgium
| | - Herre S J van der Zant
- Department of Quantum Nanoscience, Kavli Institute of Nanoscience, Technical University Delft, Lorentzweg 1, 2628 CJ, Delft, The Netherlands
| | - Henricus T S Boschker
- Department of Biology, University of Antwerp, Universiteitsplein 1, B-2610, Wilrijk, Belgium.,Department of Biotechnology, Delft University of Technology, Van der Maasweg 9, 2629HZ, Delft, The Netherlands
| | - Jean V Manca
- X-LAB, Hasselt University, Agoralaan D, B-3590, Diepenbeek, Belgium
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52
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Abstract
Cable bacteria of the family Desulfobulbaceae form centimeter-long filaments comprising thousands of cells. They occur worldwide in the surface of aquatic sediments, where they connect sulfide oxidation with oxygen or nitrate reduction via long-distance electron transport. In the absence of pure cultures, we used single-filament genomics and metagenomics to retrieve draft genomes of 3 marine Candidatus Electrothrix and 1 freshwater Ca. Electronema species. These genomes contain >50% unknown genes but still share their core genomic makeup with sulfate-reducing and sulfur-disproportionating Desulfobulbaceae, with few core genes lost and 212 unique genes (from 197 gene families) conserved among cable bacteria. Last common ancestor analysis indicates gene divergence and lateral gene transfer as equally important origins of these unique genes. With support from metaproteomics of a Ca. Electronema enrichment, the genomes suggest that cable bacteria oxidize sulfide by reversing the canonical sulfate reduction pathway and fix CO2 using the Wood-Ljungdahl pathway. Cable bacteria show limited organotrophic potential, may assimilate smaller organic acids and alcohols, fix N2, and synthesize polyphosphates and polyglucose as storage compounds; several of these traits were confirmed by cell-level experimental analyses. We propose a model for electron flow from sulfide to oxygen that involves periplasmic cytochromes, yet-unidentified conductive periplasmic fibers, and periplasmic oxygen reduction. This model proposes that an active cable bacterium gains energy in the anodic, sulfide-oxidizing cells, whereas cells in the oxic zone flare off electrons through intense cathodic oxygen respiration without energy conservation; this peculiar form of multicellularity seems unparalleled in the microbial world.
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53
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Zhao J, Wang L, Tang L, Ren R, You W, Farooq R, Wang Z, Zhang Y. Changes in bacterial community structure and humic acid composition in response to enhanced extracellular electron transfer process in coastal sediment. Arch Microbiol 2019; 201:897-906. [DOI: 10.1007/s00203-019-01659-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2018] [Revised: 02/25/2019] [Accepted: 04/10/2019] [Indexed: 12/24/2022]
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54
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Kirmizakis P, Doherty R, Mendonça CA, Costeira R, Allen CCR, Ofterdinger US, Kulakov L. Enhancement of gasworks groundwater remediation by coupling a bio-electrochemical and activated carbon system. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2019; 26:9981-9991. [PMID: 30739291 PMCID: PMC6469603 DOI: 10.1007/s11356-019-04297-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/18/2018] [Accepted: 01/18/2019] [Indexed: 05/03/2023]
Abstract
Here, we show the electrical response, bacterial community, and remediation of hydrocarbon-contaminated groundwater from a gasworks site using a graphite-chambered bio-electrochemical system (BES) that utilizes granular activated carbon (GAC) as both sorption agent and high surface area anode. Our innovative concept is the design of a graphite electrode chamber system rather than a classic non-conductive BES chamber coupled with GAC as part of the BES. The GAC BES is a good candidate as a sustainable remediation technology that provides improved degradation over GAC, and near real-time observation of associated electrical output. The BES chambers were effectively colonized by the bacterial communities from the contaminated groundwater. Principal coordinate analysis (PCoA) of UniFrac Observed Taxonomic Units shows distinct grouping of microbial types that are associated with the presence of GAC, and grouping of microbial types associated with electroactivity. Bacterial community analysis showed that β-proteobacteria (particularly the PAH-degrading Pseudomonadaceae) dominate all the samples. Rhodocyclaceae- and Comamonadaceae-related OTU were observed to increase in BES cells. The GAC BES (99% removal) outperformed the control graphite GAC chamber, as well as a graphite BES and a control chamber both filled with glass beads.
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Affiliation(s)
- Panagiotis Kirmizakis
- School of the Natural and Built Environment, Queen's University Belfast, Stranmillis Road, Belfast, BT9 5AG, UK
| | - Rory Doherty
- School of the Natural and Built Environment, Queen's University Belfast, Stranmillis Road, Belfast, BT9 5AG, UK.
| | - Carlos A Mendonça
- Department of Geophysics, University of São Paulo, Rua do Matão, São Paulo, 1226, Brazil
| | - Ricardo Costeira
- School of Biological Sciences, Queen's University Belfast, Lisburn Road, Belfast, BT9 7BL, UK
| | - Chris C R Allen
- School of Biological Sciences, Queen's University Belfast, Lisburn Road, Belfast, BT9 7BL, UK
- Institute for Global Food Security, Queen's University Belfast, Lisburn Road, Belfast, BT9 7BL, UK
| | - Ulrich S Ofterdinger
- School of the Natural and Built Environment, Queen's University Belfast, Stranmillis Road, Belfast, BT9 5AG, UK
| | - Leonid Kulakov
- School of Biological Sciences, Queen's University Belfast, Lisburn Road, Belfast, BT9 7BL, UK
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55
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Costeira R, Doherty R, Allen CCR, Larkin MJ, Kulakov LA. Analysis of viral and bacterial communities in groundwater associated with contaminated land. THE SCIENCE OF THE TOTAL ENVIRONMENT 2019; 656:1413-1426. [PMID: 30625669 DOI: 10.1016/j.scitotenv.2018.11.429] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2018] [Revised: 11/24/2018] [Accepted: 11/28/2018] [Indexed: 06/09/2023]
Abstract
This work aimed at the comprehensive analysis of total microbial communities inhabiting a typical hydrocarbon-polluted site, where chemical characteristics of the groundwater were readily available. To achieve this, a joint metagenomic characterization of bacteria and viruses surrounding a contaminant plume was performed over a one-year period. The results presented demonstrated that both potential hydrocarbon degraders and their bacteriophages were dominant around the plume, and that the viral and bacterial diversities found at the site were probably influenced by the pH of the groundwater. Niche-specific and dispersed associations between phages and bacteria were identified. The niche phage-host associations were found at the edge of the site and at the core of the plume where pH was the highest (9.52). The identified host populations included several classes of bacteria (e.g. Clostridia and Proteobacteria). Thirty-six viral generalists were also discovered, with BGW-G9 having the broadest host range across 23 taxa, including Pseudomonas, Polycyclovorans, Methylocaldum and Candidatus Magnetobacterium species. The phages with broad host ranges are presumed to have significant effects on prokaryotic production and horizontal gene transfer, and therefore impact the biodegradation processes conducted by various bacteria of the environment studied. This study for the first time characterized the phages and their bacterial hosts associated with a contaminant plume.
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Affiliation(s)
| | - Rory Doherty
- School of the Natural and Built Environment, Queen's University Belfast, UK
| | - Christopher C R Allen
- School of Biological Sciences, Queen's University Belfast, UK; Institute for Global Food Security, Queen's University Belfast, UK
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56
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Ni G, Harnawan P, Seidel L, Ter Heijne A, Sleutels T, Buisman CJN, Dopson M. Haloalkaliphilic microorganisms assist sulfide removal in a microbial electrolysis cell. JOURNAL OF HAZARDOUS MATERIALS 2019; 363:197-204. [PMID: 30308358 DOI: 10.1016/j.jhazmat.2018.09.049] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2018] [Revised: 09/17/2018] [Accepted: 09/19/2018] [Indexed: 06/08/2023]
Abstract
Several industrial processes produce toxic sulfide containing streams that are often scrubbed using caustic solutions. An alternative, cost effective sulfide treatment method is bioelectrochemical sulfide removal. For the first time, a haloalkaliphilic sulfide-oxidizing microbial consortium was introduced to the anodic chamber of a microbial electrolysis cell operated at alkaline pH and with 1.0 M sodium ions. Under anode potential control, the highest sulfide removal rate was 2.16 mM/day and chemical analysis supported that the electrical current generation was from the sulfide oxidation. Biotic operation produced a maximum current density of 3625 mA/m2 compared to 210 mA/m2 while under abiotic operation. Furthermore, biotic electrical production was maintained for a longer period than for abiotic operation, potentially due to the passivation of the electrode by elemental sulfur during abiotic operation. The use of microorganisms reduced the energy input in this study compared to published electrochemical sulfide removal technologies. Sulfide-oxidizing populations dominated both the planktonic and electrode-attached communities with 16S rRNA gene sequences aligning within the genera Thioalkalivibrio, Thioalkalimicrobium, and Desulfurivibrio. The dominance of the Desulfurivibrio-like population on the anode surface offered evidence for the first haloalkaliphilic bacterium able to couple electrons from sulfide oxidation to extracellular electron transfer to the anode.
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Affiliation(s)
- Gaofeng Ni
- Wetsus, European Centre of Excellence for Sustainable Water Technology, Oostergoweg 9, P.O. Box 1113, Leeuwarden, 8911 MA, the Netherlands; Centre for Ecology and Evolution in Microbial Model Systems (EEMiS), Linnaeus University, Kalmar, Sweden.
| | - Pebrianto Harnawan
- Wetsus, European Centre of Excellence for Sustainable Water Technology, Oostergoweg 9, P.O. Box 1113, Leeuwarden, 8911 MA, the Netherlands
| | - Laura Seidel
- Centre for Ecology and Evolution in Microbial Model Systems (EEMiS), Linnaeus University, Kalmar, Sweden
| | - Annemiek Ter Heijne
- Sub-Department of Environmental Technology, Wageningen University, Bornse Weilanden 9, P.O. Box 17, 6700 AA, Wageningen, the Netherlands
| | - Tom Sleutels
- Wetsus, European Centre of Excellence for Sustainable Water Technology, Oostergoweg 9, P.O. Box 1113, Leeuwarden, 8911 MA, the Netherlands
| | - Cees J N Buisman
- Wetsus, European Centre of Excellence for Sustainable Water Technology, Oostergoweg 9, P.O. Box 1113, Leeuwarden, 8911 MA, the Netherlands; Sub-Department of Environmental Technology, Wageningen University, Bornse Weilanden 9, P.O. Box 17, 6700 AA, Wageningen, the Netherlands
| | - Mark Dopson
- Centre for Ecology and Evolution in Microbial Model Systems (EEMiS), Linnaeus University, Kalmar, Sweden
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57
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Fernandez PM, Binley A, Bloem E, French HK. Laboratory spectral induced polarisation signatures associated with iron and manganese oxide dissolution because of anaerobic degradation. JOURNAL OF CONTAMINANT HYDROLOGY 2019; 221:1-10. [PMID: 30600103 DOI: 10.1016/j.jconhyd.2018.12.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/15/2018] [Revised: 12/05/2018] [Accepted: 12/15/2018] [Indexed: 06/09/2023]
Abstract
Degradation of organic chemicals in natural soils depends on oxidation-reduction conditions. To protect our groundwater resources we need to understand the degradation processes under anaerobic conditions. Available iron and manganese oxides are used as electron acceptors for anaerobic degradation and are reduced to the dissolved form of metallic cations in pore water. To monitor this process is a challenge, because anaerobic conditions are difficult to sample directly without introducing oxygen. A few studies have shown an impact of iron reduction on spectral induced polarisation (SIP) signature, often associated with bacterial growth. Our objective is to study the impact of iron and manganese oxide dissolution, caused by degradation of an organic compound, with spectral induced polarisation signatures. Twenty-six vertical columns (30 cm high, inner diameter 4.6 cm) were filled with a sand rich in oxides (manganese and iron) with a static water table in the middle. In half of the columns, a 2 cm high contaminated layer was installed just above the water table. As the contaminant degrades, the initial oxygen is consumed and anaerobic conditions form Every three days over a period of one month, spectral induced polarisation (twenty frequencies between 5mHz and 10 kHz) data were collected on six columns: three contaminated replicates and three control replicates. Chemical analysis was done on twenty columns assigned for destructive water sampling, ten contaminated columns and ten control. The results show an increase of the real conductivity associated with the degradation processes, independent of frequency. Compared with the pore water electrical conductivity in the saturated zone, the real conductivity measurement revealed the formation of surface conductivity before iron was released in the pore water. In parallel, we also observed an evolution of the imaginary conductivity in both saturated and unsaturated zones at frequencies below 1 Hz. Overall, the anaerobic reduction of iron and manganese oxide during the organic degradation increased both the conductive and polarisation component of the complex conductivity.
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Affiliation(s)
- Perrine M Fernandez
- Norwegian University of Life Sciences (NMBU), Universitetstunet 3, 1430 Ås, Norway.
| | - Andrew Binley
- Lancaster Environment Centre, Lancaster University, Lancaster LA1 4YQ, United Kingdom.
| | - Esther Bloem
- Norwegian Institute of Bioeconomy Research (NIBIO), Høgskoleveien 7, 1430 Ås, Norway.
| | - Helen K French
- Norwegian University of Life Sciences (NMBU), Universitetstunet 3, 1430 Ås, Norway; Norwegian Institute of Bioeconomy Research (NIBIO), Høgskoleveien 7, 1430 Ås, Norway.
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58
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Cornelissen R, Bøggild A, Thiruvallur Eachambadi R, Koning RI, Kremer A, Hidalgo-Martinez S, Zetsche EM, Damgaard LR, Bonné R, Drijkoningen J, Geelhoed JS, Boesen T, Boschker HTS, Valcke R, Nielsen LP, D'Haen J, Manca JV, Meysman FJR. The Cell Envelope Structure of Cable Bacteria. Front Microbiol 2018; 9:3044. [PMID: 30619135 PMCID: PMC6307468 DOI: 10.3389/fmicb.2018.03044] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2018] [Accepted: 11/26/2018] [Indexed: 11/16/2022] Open
Abstract
Cable bacteria are long, multicellular micro-organisms that are capable of transporting electrons from cell to cell along the longitudinal axis of their centimeter-long filaments. The conductive structures that mediate this long-distance electron transport are thought to be located in the cell envelope. Therefore, this study examines in detail the architecture of the cell envelope of cable bacterium filaments by combining different sample preparation methods (chemical fixation, resin-embedding, and cryo-fixation) with a portfolio of imaging techniques (scanning electron microscopy, transmission electron microscopy and tomography, focused ion beam scanning electron microscopy, and atomic force microscopy). We systematically imaged intact filaments with varying diameters. In addition, we investigated the periplasmic fiber sheath that remains after the cytoplasm and membranes were removed by chemical extraction. Based on these investigations, we present a quantitative structural model of a cable bacterium. Cable bacteria build their cell envelope by a parallel concatenation of ridge compartments that have a standard size. Larger diameter filaments simply incorporate more parallel ridge compartments. Each ridge compartment contains a ~50 nm diameter fiber in the periplasmic space. These fibers are continuous across cell-to-cell junctions, which display a conspicuous cartwheel structure that is likely made by invaginations of the outer cell membrane around the periplasmic fibers. The continuity of the periplasmic fibers across cells makes them a prime candidate for the sought-after electron conducting structure in cable bacteria.
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Affiliation(s)
| | - Andreas Bøggild
- Center for Electromicrobiology, Department of Bioscience Aarhus University, Aarhus, Denmark.,Interdisciplinary Nanoscience Center and Department of Molecular Biology and Genetics, Structural Biology Aarhus University, Aarhus, Denmark
| | | | - Roman I Koning
- Department of Cell and Chemical Biology, Leiden University Medical Center, Leiden, Netherlands
| | - Anna Kremer
- Bio-imaging Core, Flemish Institute of Biotechnology (VIB), Gent, Belgium
| | | | - Eva-Maria Zetsche
- Department of Marine Sciences, University of Gothenburg, Gothenburg, Sweden
| | - Lars R Damgaard
- Center for Electromicrobiology, Department of Bioscience Aarhus University, Aarhus, Denmark
| | | | | | | | - Thomas Boesen
- Center for Electromicrobiology, Department of Bioscience Aarhus University, Aarhus, Denmark.,Interdisciplinary Nanoscience Center and Department of Molecular Biology and Genetics, Structural Biology Aarhus University, Aarhus, Denmark
| | - Henricus T S Boschker
- Department of Biology, University of Antwerp, Antwerpen, Belgium.,Department of Biotechnology, Delft University of Technology, Delft, Netherlands
| | - Roland Valcke
- Molecular and Physical Plant Physiology, Hasselt University, Hasselt, Belgium
| | - Lars Peter Nielsen
- Center for Electromicrobiology, Department of Bioscience Aarhus University, Aarhus, Denmark
| | - Jan D'Haen
- Institute for Materials Research (IMO), Hasselt University, Hasselt, Belgium
| | | | - Filip J R Meysman
- Department of Biology, University of Antwerp, Antwerpen, Belgium.,Department of Biotechnology, Delft University of Technology, Delft, Netherlands
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59
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In vitro single-cell dissection revealing the interior structure of cable bacteria. Proc Natl Acad Sci U S A 2018; 115:8517-8522. [PMID: 30082405 DOI: 10.1073/pnas.1807562115] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Filamentous Desulfobulbaceae bacteria were recently discovered as long-range transporters of electrons from sulfide to oxygen in marine sediments. The long-range electron transfer through these cable bacteria has created considerable interests, but it has also raised many questions, such as what structural basis will be required to enable micrometer-sized cells to build into centimeter-long continuous filaments? Here we dissected cable bacteria cells in vitro by atomic force microscopy and further explored the interior, which is normally hidden behind the outer membrane. Using nanoscale topographical and mechanical maps, different types of bacterial cell-cell junctions and strings along the cable length were identified. More important, these strings were found to be continuous along the bacterial cells passing through the cell-cell junctions. This indicates that the strings serve an important function in maintaining integrity of individual cable bacteria cells as a united filament. Furthermore, ridges in the outer membrane are found to envelop the individual strings at cell-cell junctions, and they are proposed to strengthen the junctions. Finally, we propose a model for the division and growth of the cable bacteria, which illustrate the possible structural requirements for the formation of centimeter-length filaments in the recently discovered cable bacteria.
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60
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Microbial electrocatalysis: Redox mediators responsible for extracellular electron transfer. Biotechnol Adv 2018; 36:1815-1827. [PMID: 30196813 DOI: 10.1016/j.biotechadv.2018.07.001] [Citation(s) in RCA: 103] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2018] [Revised: 07/03/2018] [Accepted: 07/05/2018] [Indexed: 11/21/2022]
Abstract
Redox mediator plays an important role in extracellular electron transfer (EET) in many environments wherein microbial electrocatalysis occurs actively. Because of the block of cell envelope and the low difference of redox potential between the intracellular and extracellular surroundings, the proceeding of EET depends mainly on the help of a variety of mediators that function as an electron carrier or bridge. In this Review, we will summarize a wide range of redox mediators and further discuss their functional mechanisms in EET that drives a series of microbial electrocatalytic reactions. Studying these mediators adds to our knowledge of how charge transport and electrochemical reactions occur at the microorganism-electrode interface. This understanding would promote the widespread applications of microbial electrocatalysis in microbial fuel cells, bioremediation, bioelectrosynthesis, biomining, nanomaterial productions, etc. These improved applications will greatly benefit the sustainable development of the environmental-friendly biochemical industries.
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61
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Cable Bacteria Take a New Breath Using Long-Distance Electricity. Trends Microbiol 2018; 26:411-422. [DOI: 10.1016/j.tim.2017.10.011] [Citation(s) in RCA: 49] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2017] [Revised: 10/29/2017] [Accepted: 10/31/2017] [Indexed: 11/18/2022]
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62
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Daghio M, Espinoza Tofalos A, Leoni B, Cristiani P, Papacchini M, Jalilnejad E, Bestetti G, Franzetti A. Bioelectrochemical BTEX removal at different voltages: assessment of the degradation and characterization of the microbial communities. JOURNAL OF HAZARDOUS MATERIALS 2018; 341:120-127. [PMID: 28772251 DOI: 10.1016/j.jhazmat.2017.07.054] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/12/2017] [Revised: 06/23/2017] [Accepted: 07/22/2017] [Indexed: 05/20/2023]
Abstract
BTEX compounds (Benzene, Toluene, Ethylbenzene and Xylenes) are toxic hydrocarbons that can be found in groundwater due to accidental spills. Bioelectrochemical systems (BES) are an innovative technology to stimulate the anaerobic degradation of hydrocarbons. In this work, single chamber BESs were used to assess the degradation of a BTEX mixture at different applied voltages (0.8V, 1.0V, 1.2V) between the electrodes. Hydrocarbon degradation was linked to current production and to sulfate reduction, at all the tested potentials. The highest current densities (about 200mA/m2 with a maximum peak at 480mA/m2) were observed when 0.8V were applied. The application of an external voltage increased the removal of toluene, m-xylene and p-xylene. The highest removal rate constants at 0.8V were: 0.4±0.1days-1, 0.34±0.09days-1 and 0.16±0.02days-1, respectively. At the end of the experiment, the microbial communities were characterized by high throughput sequencing of the 16S rRNA gene. Microorganisms belonging to the families Desulfobulbaceae, Desulfuromonadaceae and Geobacteraceae were enriched on the anodes suggesting that both direct electron transfer and sulfur cycling occurred. The cathodic communities were dominated by the family Desulfomicrobiaceae that may be involved in hydrogen production.
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Affiliation(s)
- Matteo Daghio
- Department of Earth and Environmental Sciences - University of Milano-Bicocca, Piazza della Scienza 1, 20126, Milano, Italy
| | - Anna Espinoza Tofalos
- Department of Earth and Environmental Sciences - University of Milano-Bicocca, Piazza della Scienza 1, 20126, Milano, Italy; Department of Chemistry, Universidad Técnica Federico Santa María, Av. España 1680, Valparaíso, Chile
| | - Barbara Leoni
- Department of Earth and Environmental Sciences - University of Milano-Bicocca, Piazza della Scienza 1, 20126, Milano, Italy
| | - Pierangela Cristiani
- Ricerca sul Sistema Energetico - RSE Spa, Department of Sustainable Development and Energy Sources, Via Rubattino, 54, 20134 Milan, Italy
| | - Maddalena Papacchini
- INAIL Settore Ricerca, Certificazione e Verifica, Dipartimento di Innovazione Tecnologica (DIT) Laboratorio di Biotecnologie, Rome, Italy
| | - Elham Jalilnejad
- Department of Earth and Environmental Sciences - University of Milano-Bicocca, Piazza della Scienza 1, 20126, Milano, Italy; Faculty of Chemical Engineering, Urmia University of Technology, Urmia, Iran
| | - Giuseppina Bestetti
- Department of Earth and Environmental Sciences - University of Milano-Bicocca, Piazza della Scienza 1, 20126, Milano, Italy
| | - Andrea Franzetti
- Department of Earth and Environmental Sciences - University of Milano-Bicocca, Piazza della Scienza 1, 20126, Milano, Italy.
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63
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Anaerobic degradation of 1-methylnaphthalene by a member of the Thermoanaerobacteraceae contained in an iron-reducing enrichment culture. Biodegradation 2017; 29:23-39. [PMID: 29177812 PMCID: PMC5773621 DOI: 10.1007/s10532-017-9811-z] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2017] [Accepted: 11/02/2017] [Indexed: 11/13/2022]
Abstract
An anaerobic culture (1MN) was enriched with 1-methylnaphthalene as sole source of carbon and electrons and Fe(OH)3 as electron acceptor. 1-Naphthoic acid was produced as a metabolite during growth with 1-methylnaphthalene while 2-naphthoic acid was detected with naphthalene and 2-methylnaphthalene. This indicates that the degradation pathway of 1-methylnaphthalene might differ from naphthalene and 2-methylnaphthalene degradation in sulfate reducers. Terminal restriction fragment length polymorphism and pyrosequencing revealed that the culture is mainly composed of two bacteria related to uncultured Gram-positive Thermoanaerobacteraceae and uncultured gram-negative Desulfobulbaceae. Stable isotope probing showed that a 13C-carbon label from 13C10-naphthalene as growth substrate was mostly incorporated by the Thermoanaerobacteraceae. The presence of putative genes involved in naphthalene degradation in the genome of this organism was confirmed via assembly-based metagenomics and supports that it is the naphthalene-degrading bacterium in the culture. Thermoanaerobacteraceae have previously been detected in oil sludge under thermophilic conditions, but have not been shown to degrade hydrocarbons so far. The second member of the community belongs to the Desulfobulbaceae and has high sequence similarity to uncultured bacteria from contaminated sites including recently proposed groundwater cable bacteria. We suggest that the gram-positive Thermoanaerobacteraceae degrade polycyclic aromatic hydrocarbons while the Desulfobacterales are mainly responsible for Fe(III) reduction.
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64
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Electrically conductive pili from pilin genes of phylogenetically diverse microorganisms. ISME JOURNAL 2017; 12:48-58. [PMID: 28872631 DOI: 10.1038/ismej.2017.141] [Citation(s) in RCA: 107] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/17/2017] [Revised: 06/17/2017] [Accepted: 07/25/2017] [Indexed: 11/08/2022]
Abstract
The possibility that bacteria other than Geobacter species might contain genes for electrically conductive pili (e-pili) was investigated by heterologously expressing pilin genes of interest in Geobacter sulfurreducens. Strains of G. sulfurreducens producing high current densities, which are only possible with e-pili, were obtained with pilin genes from Flexistipes sinusarabici, Calditerrivibrio nitroreducens and Desulfurivibrio alkaliphilus. The conductance of pili from these strains was comparable to native G. sulfurreducens e-pili. The e-pili derived from C. nitroreducens, and D. alkaliphilus pilin genes are the first examples of relatively long (>100 amino acids) pilin monomers assembling into e-pili. The pilin gene from Candidatus Desulfofervidus auxilii did not yield e-pili, suggesting that the hypothesis that this sulfate reducer wires itself with e-pili to methane-oxidizing archaea to enable anaerobic methane oxidation should be reevaluated. A high density of aromatic amino acids and a lack of substantial aromatic-free gaps along the length of long pilins may be important characteristics leading to e-pili. This study demonstrates a simple method to screen pilin genes from difficult-to-culture microorganisms for their potential to yield e-pili; reveals new sources for biologically based electronic materials; and suggests that a wide phylogenetic diversity of microorganisms may use e-pili for extracellular electron exchange.
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65
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Li C, Lesnik KL, Liu H. Stay connected: Electrical conductivity of microbial aggregates. Biotechnol Adv 2017; 35:669-680. [PMID: 28768145 DOI: 10.1016/j.biotechadv.2017.07.010] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2017] [Revised: 07/25/2017] [Accepted: 07/27/2017] [Indexed: 01/01/2023]
Abstract
The discovery of direct extracellular electron transfer offers an alternative to the traditional understanding of diffusional electron exchange via small molecules. The establishment of electronic connections between electron donors and acceptors in microbial communities is critical to electron transfer via electrical currents. These connections are facilitated through conductivity associated with various microbial aggregates. However, examination of conductivity in microbial samples is still in its relative infancy and conceptual models in terms of conductive mechanisms are still being developed and debated. The present review summarizes the fundamental understanding of electrical conductivity in microbial aggregates (e.g. biofilms, granules, consortia, and multicellular filaments) highlighting recent findings and key discoveries. A greater understanding of electrical conductivity in microbial aggregates could facilitate the survey for additional microbial communities that rely on direct extracellular electron transfer for survival, inform rational design towards the aggregates-based production of bioenergy/bioproducts, and inspire the construction of new synthetic conductive polymers.
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Affiliation(s)
- Cheng Li
- Biological and Ecological Engineering, Oregon State University, Corvallis, OR 97333, USA
| | - Keaton Larson Lesnik
- Biological and Ecological Engineering, Oregon State University, Corvallis, OR 97333, USA
| | - Hong Liu
- Biological and Ecological Engineering, Oregon State University, Corvallis, OR 97333, USA.
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66
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Schmidt I, Pieper A, Wichmann H, Bunk B, Huber K, Overmann J, Walla PJ, Schröder U. In Situ Autofluorescence Spectroelectrochemistry for the Study of Microbial Extracellular Electron Transfer. ChemElectroChem 2017. [DOI: 10.1002/celc.201700675] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Igor Schmidt
- Institute of Environmental and Sustainable Chemistry; Technische Universität Braunschweig; 38106 Braunschweig Germany
| | - Alexander Pieper
- Department of Biophysical Chemistry, Institute for Physical and Theoretical Chemistry; Technische Universität Braunschweig; 38106 Braunschweig, Germany
| | - Hilke Wichmann
- Institute of Environmental and Sustainable Chemistry; Technische Universität Braunschweig; 38106 Braunschweig Germany
| | - Boyke Bunk
- Department Microbial Ecology and Diversity Research; Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures; 38124 Braunschweig Germany
| | - Katharina Huber
- Department Microbial Ecology and Diversity Research; Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures; 38124 Braunschweig Germany
| | - Jörg Overmann
- Department Microbial Ecology and Diversity Research; Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures; 38124 Braunschweig Germany
| | - Peter Jomo Walla
- Department of Biophysical Chemistry, Institute for Physical and Theoretical Chemistry; Technische Universität Braunschweig; 38106 Braunschweig, Germany
| | - Uwe Schröder
- Institute of Environmental and Sustainable Chemistry; Technische Universität Braunschweig; 38106 Braunschweig Germany
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67
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Taran O. Electron Transfer between Electrically Conductive Minerals and Quinones. Front Chem 2017; 5:49. [PMID: 28752088 PMCID: PMC5508016 DOI: 10.3389/fchem.2017.00049] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2016] [Accepted: 06/21/2017] [Indexed: 01/04/2023] Open
Abstract
Long-distance electron transfer in marine environments couples physically separated redox half-reactions, impacting biogeochemical cycles of iron, sulfur and carbon. Bacterial bio-electrochemical systems that facilitate electron transfer via conductive filaments or across man-made electrodes are well-known, but the impact of abiotic currents across naturally occurring conductive and semiconductive minerals is poorly understood. In this paper I use cyclic voltammetry to explore electron transfer between electrodes made of common iron minerals (magnetite, hematite, pyrite, pyrrhotite, mackinawite, and greigite), and hydroquinones—a class of organic molecules found in carbon-rich sediments. Of all tested minerals, only pyrite and magnetite showed an increase in electric current in the presence of organic molecules, with pyrite showing excellent electrocatalytic performance. Pyrite electrodes performed better than commercially available glassy carbon electrodes and showed higher peak currents, lower overpotential values and a smaller separation between oxidation and reduction peaks for each tested quinone. Hydroquinone oxidation on pyrite surfaces was reversible, diffusion controlled, and stable over a large number of potential cycles. Given the ubiquity of both pyrite and quinones, abiotic electron transfer between minerals and organic molecules is likely widespread in Nature and may contribute to several different phenomena, including anaerobic respiration of a wide variety of microorganisms in temporally anoxic zones or in the proximity of hydrothermal vent chimneys, as well as quinone cycling and the propagation of anoxic zones in organic rich waters. Finally, interactions between pyrite and quinones make use of electrochemical gradients that have been suggested as an important source of energy for the origins of life on Earth. Ubiquinones and iron sulfide clusters are common redox cofactors found in electron transport chains across all domains of life and interactions between quinones and pyrite might have been an early analog of these ubiquitous systems.
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Affiliation(s)
- Olga Taran
- Department of Chemistry, Emory UniversityAtlanta, GA, United States
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68
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Rudrashetti AP, Jadeja NB, Gandhi D, Juwarkar AA, Sharma A, Kapley A, Pandey RA. Microbial population shift caused by sulfamethoxazole in engineered-Soil Aquifer Treatment (e-SAT) system. World J Microbiol Biotechnol 2017; 33:121. [PMID: 28523623 DOI: 10.1007/s11274-017-2284-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2017] [Accepted: 05/11/2017] [Indexed: 12/01/2022]
Abstract
The engineered-Soil Aquifer Treatment (e-SAT) system was exploited for the biological degradation of Sulfamethoxazole (SMX) which is known to bio-accumulate in the environment. The fate of SMX in soil column was studied through laboratory simulation for a period of 90 days. About 20 ppm SMX concentration could be removed in four consecutive cycles in e-SAT. To understand the microbial community change and biological degradation of SMX in e-SAT system, metagenomic analysis was performed for the soil samples before (A-EBD) and after SMX exposure (B-EBD) in the e-SAT. Four bacterial phyla were found to be present in both the samples, with sample B-EBD showing increased abundance for Actinobacteria, Bacteroidetes, Firmicutes and decreased Proteobacterial abundance compared to A-EBD. The unclassified bacteria were found to be abundant in B-EBD compared to A-EBD. At class level, classes such as Bacilli, Negativicutes, Deltaproteobacteria, and Bacteroidia emerged in sample B-EBD owing to SMX treatment, while Burkholderiales and Nitrosomonadales appeared to be dominant at order level after SMX treatment. Furthermore, in response to SMX treatment, the family Nitrosomonadaceae appeared to be dominant. Pseudomonas was the most dominating bacterial genus in A-EBD whereas Cupriavidus dominated in sample B-EBD. Additionally, the sulfur oxidizing bacteria were enriched in the B-EBD sample, signifying efficient electron transfer and hence organic molecule degradation in the e-SAT system. Results of this study offer new insights into understanding of microbial community shift during the biodegradation of SMX.
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Affiliation(s)
| | - Niti B Jadeja
- CSIR-National Environmental Engineering Research Institute (NEERI), Nagpur, India
| | - Deepa Gandhi
- CSIR-National Environmental Engineering Research Institute (NEERI), Nagpur, India
| | - Asha A Juwarkar
- CSIR-National Environmental Engineering Research Institute (NEERI), Nagpur, India
| | - Abhinav Sharma
- CSIR-National Environmental Engineering Research Institute (NEERI), Nagpur, India
| | - Atya Kapley
- CSIR-National Environmental Engineering Research Institute (NEERI), Nagpur, India
| | - R A Pandey
- CSIR-National Environmental Engineering Research Institute (NEERI), Nagpur, India.
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69
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Zhu B, Bradford L, Huang S, Szalay A, Leix C, Weissbach M, Táncsics A, Drewes JE, Lueders T. Unexpected Diversity and High Abundance of Putative Nitric Oxide Dismutase (Nod) Genes in Contaminated Aquifers and Wastewater Treatment Systems. Appl Environ Microbiol 2017; 83:e02750-16. [PMID: 27986721 PMCID: PMC5288823 DOI: 10.1128/aem.02750-16] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2016] [Accepted: 12/02/2016] [Indexed: 11/20/2022] Open
Abstract
It has recently been suggested that oxygenic dismutation of NO into N2 and O2 may occur in the anaerobic methanotrophic "Candidatus Methylomirabilis oxyfera" and the alkane-oxidizing gammaproteobacterium HdN1. It may represent a new pathway in microbial nitrogen cycling catalyzed by a putative NO dismutase (Nod). The formed O2 enables microbes to employ aerobic catabolic pathways in anoxic habitats, suggesting an ecophysiological niche space of substantial appeal for bioremediation and water treatment. However, it is still unknown whether this physiology is limited to "Ca Methylomirabilis oxyfera" and HdN1 and whether it can be coupled to the oxidation of electron donors other than alkanes. Here, we report insights into an unexpected diversity and remarkable abundance of nod genes in natural and engineered water systems. Phylogenetically diverse nod genes were recovered from a range of contaminated aquifers and N-removing wastewater treatment systems. Together with nod genes from "Ca Methylomirabilis oxyfera" and HdN1, the novel environmental nod sequences formed no fewer than 6 well-supported phylogenetic clusters, clearly distinct from canonical NO reductase (quinol-dependent NO reductase [qNor] and cytochrome c-dependent NO reductase [cNor]) genes. The abundance of nod genes in the investigated samples ranged from 1.6 × 107 to 5.2 × 1010 copies · g-1 (wet weight) of sediment or sludge biomass, accounting for up to 10% of total bacterial 16S rRNA gene counts. In essence, NO dismutation could be a much more widespread physiology than currently perceived. Understanding the controls of this emergent microbial capacity could offer new routes for nitrogen elimination or pollutant remediation in natural and engineered water systems. IMPORTANCE NO dismutation into N2 and O2 is a novel process catalyzed by putative NO dismutase (Nod). To date, only two bacteria, the anaerobic methane-oxidizing bacterium "Ca Methylomirabilis oxyfera" and the alkane-oxidizing gammaproteobacterium HdN1, are known to harbor nod genes. In this study, we report efficient molecular tools that can detect and quantify a wide diversity of nod genes in environmental samples. A surprisingly high diversity and abundance of nod genes were found in contaminated aquifers as well as wastewater treatment systems. This evidence indicates that NO dismutation may be a much more widespread physiology in natural and man-made environments than currently perceived. The molecular tools presented here will facilitate further studies on these enigmatic microbes in the future.
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Affiliation(s)
- Baoli Zhu
- Institute of Groundwater Ecology, Helmholtz-Zentrum München, Neuherberg, Germany
| | - Lauren Bradford
- Institute of Groundwater Ecology, Helmholtz-Zentrum München, Neuherberg, Germany
| | - Sichao Huang
- Institute of Groundwater Ecology, Helmholtz-Zentrum München, Neuherberg, Germany
| | - Anna Szalay
- Institute of Groundwater Ecology, Helmholtz-Zentrum München, Neuherberg, Germany
| | - Carmen Leix
- Chair of Urban Water Systems Engineering, Technical University of Munich, Munich, Germany
| | - Max Weissbach
- Chair of Urban Water Systems Engineering, Technical University of Munich, Munich, Germany
| | | | - Jörg E Drewes
- Chair of Urban Water Systems Engineering, Technical University of Munich, Munich, Germany
| | - Tillmann Lueders
- Institute of Groundwater Ecology, Helmholtz-Zentrum München, Neuherberg, Germany
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70
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Stolz JF. Gaia and her microbiome. FEMS Microbiol Ecol 2016; 93:fiw247. [DOI: 10.1093/femsec/fiw247] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Revised: 10/03/2016] [Accepted: 12/07/2016] [Indexed: 01/09/2023] Open
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71
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Wang K, Ye X, Zhang H, Chen H, Zhang D, Liu L. Regional variations in the diversity and predicted metabolic potential of benthic prokaryotes in coastal northern Zhejiang, East China Sea. Sci Rep 2016; 6:38709. [PMID: 27917954 PMCID: PMC5137025 DOI: 10.1038/srep38709] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2016] [Accepted: 11/11/2016] [Indexed: 12/21/2022] Open
Abstract
Knowledge about the drivers of benthic prokaryotic diversity and metabolic potential in interconnected coastal sediments at regional scales is limited. We collected surface sediments across six zones covering ~200 km in coastal northern Zhejiang, East China Sea and combined 16 S rRNA gene sequencing, community-level metabolic prediction, and sediment physicochemical measurements to investigate variations in prokaryotic diversity and metabolic gene composition with geographic distance and under local environmental conditions. Geographic distance was the most influential factor in prokaryotic β-diversity compared with major environmental drivers, including temperature, sediment texture, acid-volatile sulfide, and water depth, but a large unexplained variation in community composition suggested the potential effects of unmeasured abiotic/biotic factors and stochastic processes. Moreover, prokaryotic assemblages showed a biogeographic provincialism across the zones. The predicted metabolic gene composition similarly shifted as taxonomic composition did. Acid-volatile sulfide was strongly correlated with variation in metabolic gene composition. The enrichments in the relative abundance of sulfate-reducing bacteria and genes relevant with dissimilatory sulfate reduction were observed and predicted, respectively, in the Yushan area. These results provide insights into the relative importance of geographic distance and environmental condition in driving benthic prokaryotic diversity in coastal areas and predict specific biogeochemically-relevant genes for future studies.
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Affiliation(s)
- Kai Wang
- School of Marine Sciences, Ningbo University, Ningbo, 315211, China.,Collaborative Innovation Center for Zhejiang Marine High-efficiency and Healthy Aquaculture, Ningbo, 315211, China
| | - Xiansen Ye
- Marine Environmental Monitoring Center of Ningbo, SOA, Ningbo, 315012, China
| | - Huajun Zhang
- School of Marine Sciences, Ningbo University, Ningbo, 315211, China
| | - Heping Chen
- School of Marine Sciences, Ningbo University, Ningbo, 315211, China.,Faculty of Architectural, Civil Engineering and Environment, Ningbo University, Ningbo, 315211, China
| | - Demin Zhang
- School of Marine Sciences, Ningbo University, Ningbo, 315211, China.,Collaborative Innovation Center for Zhejiang Marine High-efficiency and Healthy Aquaculture, Ningbo, 315211, China
| | - Lian Liu
- Marine Environmental Monitoring Center of Ningbo, SOA, Ningbo, 315012, China
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72
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Lueders T. The ecology of anaerobic degraders of BTEX hydrocarbons in aquifers. FEMS Microbiol Ecol 2016; 93:fiw220. [PMID: 27810873 PMCID: PMC5400083 DOI: 10.1093/femsec/fiw220] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Revised: 06/10/2016] [Indexed: 12/24/2022] Open
Abstract
The degradation of benzene, toluene, ethylbenzene and xylene (BTEX) contaminants in groundwater relies largely on anaerobic processes. While the physiology and biochemistry of selected relevant microbes have been intensively studied, research has now started to take the generated knowledge back to the field, in order to trace the populations truly responsible for the anaerobic degradation of BTEX hydrocarbons in situ and to unravel their ecology in contaminated aquifers. Here, recent advances in our knowledge of the identity, diversity and ecology of microbes involved in these important ecosystem services are discussed. At several sites, distinct lineages within the Desulfobulbaceae, the Rhodocyclaceae and the Gram-positive Peptococcaceae have been shown to dominate the degradation of different BTEX hydrocarbons. Especially for the functional guild of anaerobic toluene degraders, specific molecular detection systems have been developed, allowing researchers to trace their diversity and distribution in contaminated aquifers. Their populations appear enriched in hot spots of biodegradation in situ. 13C-labelling experiments have revealed unexpected pathways of carbon sharing and obligate syntrophic interactions to be relevant in degradation. Together with feedback mechanisms between abiotic and biotic habitat components, this promotes an enhanced ecological perspective of the anaerobic degradation of BTEX hydrocarbons, as well as its incorporation into updated concepts for site monitoring and bioremediation.
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Affiliation(s)
- Tillmann Lueders
- Institute of Groundwater Ecology, Helmholtz Zentrum München-German Research Center for Environmental Health, 85764 Neuherberg, Germany
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