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Digel L, Justesen ML, Madsen NS, Fransaert N, Wouters K, Bonné R, Plum-Jensen LE, Marshall IPG, Jensen PB, Nicolas-Asselineau L, Drace T, Bøggild A, Hansen JL, Schramm A, Bøjesen ED, Nielsen LP, Manca JV, Boesen T. Comparison of cable bacteria genera reveals details of their conduction machinery. EMBO Rep 2025; 26:1749-1767. [PMID: 39962228 PMCID: PMC11976967 DOI: 10.1038/s44319-025-00387-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2024] [Revised: 01/29/2025] [Accepted: 01/30/2025] [Indexed: 04/09/2025] Open
Abstract
Cable bacteria are centimeter-long multicellular bacteria conducting electricity through periplasmic conductive fibers (PCFs). Using single-strain enrichments of the genera Electrothrix and Electronema we systematically investigate variations and similarities in morphology and electrical properties across both genera. Electrical conductivity of different PCFs spans three orders of magnitude warranting further investigations of the plasticity of their conduction machinery. Using electron microscopy and elemental analyses, we show that the two cable bacteria genera have similar cell envelopes and cell-cell junction ultrastructures. Iron, sulfur, and nickel signals are co-localized with the PCFs, indicating key functional roles of these elements. The PCFs are organized as stranded rope-like structures composed of multiple strands. Furthermore, we report lamellae-like structures formed at the cell-cell junctions with a core layer connecting to the PCFs, and intriguing vesicle-like inner membrane invaginations below the PCFs. Finally, using bioinformatic tools, we identify a cytochrome family with predicted structural homology to known multi-heme nanowire proteins from other electroactive microorganisms and suggest that these cytochromes can play a role in the extra- or intercellular electron conduction of cable bacteria.
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Affiliation(s)
- Leonid Digel
- Center for Electromicrobiology, Aarhus University, 8000, Aarhus, Denmark
- Department of Biology, Aarhus University, 8000, Aarhus, Denmark
- Department of Molecular Biology and Genetics, Aarhus University, 8000, Aarhus, Denmark
| | - Mads L Justesen
- Center for Electromicrobiology, Aarhus University, 8000, Aarhus, Denmark
- Department of Molecular Biology and Genetics, Aarhus University, 8000, Aarhus, Denmark
| | - Nikoline S Madsen
- Center for Electromicrobiology, Aarhus University, 8000, Aarhus, Denmark
- Department of Molecular Biology and Genetics, Aarhus University, 8000, Aarhus, Denmark
| | | | - Koen Wouters
- Center for Electromicrobiology, Aarhus University, 8000, Aarhus, Denmark
- X-LAB, UHasselt, 3500, Hasselt, Belgium
- Interdisciplinary Nanoscience Center (iNANO), Aarhus University, 8000, Aarhus, Denmark
| | - Robin Bonné
- Center for Electromicrobiology, Aarhus University, 8000, Aarhus, Denmark
- Department of Biology, Aarhus University, 8000, Aarhus, Denmark
| | - Lea E Plum-Jensen
- Center for Electromicrobiology, Aarhus University, 8000, Aarhus, Denmark
- Department of Biology, Aarhus University, 8000, Aarhus, Denmark
| | - Ian P G Marshall
- Center for Electromicrobiology, Aarhus University, 8000, Aarhus, Denmark
- Department of Biology, Aarhus University, 8000, Aarhus, Denmark
| | - Pia B Jensen
- Center for Electromicrobiology, Aarhus University, 8000, Aarhus, Denmark
- Interdisciplinary Nanoscience Center (iNANO), Aarhus University, 8000, Aarhus, Denmark
| | - Louison Nicolas-Asselineau
- Center for Electromicrobiology, Aarhus University, 8000, Aarhus, Denmark
- Max Planck Institute for Marine Microbiology, 28359, Bremen, Germany
| | - Taner Drace
- Department of Molecular Biology and Genetics, Aarhus University, 8000, Aarhus, Denmark
- EMBION - The Danish National Cryo-EM Facility - Aarhus Node, Aarhus University, 8000, Aarhus, Denmark
| | - Andreas Bøggild
- Interdisciplinary Nanoscience Center (iNANO), Aarhus University, 8000, Aarhus, Denmark
- EMBION - The Danish National Cryo-EM Facility - Aarhus Node, Aarhus University, 8000, Aarhus, Denmark
| | - John L Hansen
- Interdisciplinary Nanoscience Center (iNANO), Aarhus University, 8000, Aarhus, Denmark
- Department of Physics and Astronomy, Aarhus University, 8000, Aarhus, Denmark
| | - Andreas Schramm
- Center for Electromicrobiology, Aarhus University, 8000, Aarhus, Denmark
- Department of Biology, Aarhus University, 8000, Aarhus, Denmark
| | - Espen D Bøjesen
- Interdisciplinary Nanoscience Center (iNANO), Aarhus University, 8000, Aarhus, Denmark
- Aarhus University Centre for Integrated Materials Research, Aarhus University, 8000, Aarhus, Denmark
| | - Lars Peter Nielsen
- Center for Electromicrobiology, Aarhus University, 8000, Aarhus, Denmark
- Department of Biology, Aarhus University, 8000, Aarhus, Denmark
| | | | - Thomas Boesen
- Center for Electromicrobiology, Aarhus University, 8000, Aarhus, Denmark.
- Department of Molecular Biology and Genetics, Aarhus University, 8000, Aarhus, Denmark.
- Interdisciplinary Nanoscience Center (iNANO), Aarhus University, 8000, Aarhus, Denmark.
- EMBION - The Danish National Cryo-EM Facility - Aarhus Node, Aarhus University, 8000, Aarhus, Denmark.
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Elbon CE, Stewart FJ, Glass JB. Novel Alphaproteobacteria transcribe genes for nitric oxide transformation at high levels in a marine oxygen-deficient zone. Appl Environ Microbiol 2024; 90:e0209923. [PMID: 38445905 PMCID: PMC11022542 DOI: 10.1128/aem.02099-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2023] [Accepted: 02/09/2024] [Indexed: 03/07/2024] Open
Abstract
Marine oxygen-deficient zones (ODZs) are portions of the ocean where intense nitrogen loss occurs primarily via denitrification and anammox. Despite many decades of study, the identity of the microbes that catalyze nitrogen loss in ODZs is still being elucidated. Intriguingly, high transcription of genes in the same family as the nitric oxide dismutase (nod) gene from Methylomirabilota has been reported in the anoxic core of ODZs. Here, we show that the most abundantly transcribed nod genes in the Eastern Tropical North Pacific ODZ belong to a new order (UBA11136) of Alphaproteobacteria, rather than Methylomirabilota as previously assumed. Gammaproteobacteria and Planctomycetia also transcribe nod, but at lower relative abundance than UBA11136 in the upper ODZ. The nod-transcribing Alphaproteobacteria likely use formaldehyde and formate as a source of electrons for aerobic respiration, with additional electrons possibly from sulfide oxidation. They also transcribe multiheme cytochrome (here named ptd) genes for a putative porin-cytochrome protein complex of unknown function, potentially involved in extracellular electron transfer. Molecular oxygen for aerobic respiration may originate from nitric oxide dismutation via cryptic oxygen cycling. Our results implicate Alphaproteobacteria order UBA11136 as a significant player in marine nitrogen loss and highlight their potential in one-carbon, nitrogen, and sulfur metabolism in ODZs.IMPORTANCEIn marine oxygen-deficient zones (ODZs), microbes transform bioavailable nitrogen to gaseous nitrogen, with nitric oxide as a key intermediate. The Eastern Tropical North Pacific contains the world's largest ODZ, but the identity of the microbes transforming nitric oxide remains unknown. Here, we show that highly transcribed nitric oxide dismutase (nod) genes belong to Alphaproteobacteria of the novel order UBA11136, which lacks cultivated isolates. These Alphaproteobacteria show evidence for aerobic respiration, using oxygen potentially sourced from nitric oxide dismutase, and possess a novel porin-cytochrome protein complex with unknown function. Gammaproteobacteria and Planctomycetia transcribe nod at lower levels. Our results pinpoint the microbes mediating a key step in marine nitrogen loss and reveal an unexpected predicted metabolism for marine Alphaproteobacteria.
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Affiliation(s)
- Claire E. Elbon
- School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - Frank J. Stewart
- Department of Microbiology & Cell Biology, Montana State University, Bozeman, Montana, USA
| | - Jennifer B. Glass
- School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia, USA
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Baquero DP, Cvirkaite-Krupovic V, Hu SS, Fields JL, Liu X, Rensing C, Egelman EH, Krupovic M, Wang F. Extracellular cytochrome nanowires appear to be ubiquitous in prokaryotes. Cell 2023; 186:2853-2864.e8. [PMID: 37290436 PMCID: PMC10330847 DOI: 10.1016/j.cell.2023.05.012] [Citation(s) in RCA: 29] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2023] [Revised: 03/04/2023] [Accepted: 05/10/2023] [Indexed: 06/10/2023]
Abstract
Electrically conductive appendages from the anaerobic bacterium Geobacter sulfurreducens, recently identified as extracellular cytochrome nanowires (ECNs), have received wide attention due to numerous potential applications. However, whether other organisms employ similar ECNs for electron transfer remains unknown. Here, using cryoelectron microscopy, we describe the atomic structures of two ECNs from two major orders of hyperthermophilic archaea present in deep-sea hydrothermal vents and terrestrial hot springs. Homologs of Archaeoglobus veneficus ECN are widespread among mesophilic methane-oxidizing Methanoperedenaceae, alkane-degrading Syntrophoarchaeales archaea, and in the recently described megaplasmids called Borgs. The ECN protein subunits lack similarities in their folds; however, they share a common heme arrangement, suggesting an evolutionarily optimized heme packing for efficient electron transfer. The detection of ECNs in archaea suggests that filaments containing closely stacked hemes may be a common and widespread mechanism for long-range electron transfer in both prokaryotic domains of life.
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Affiliation(s)
- Diana P Baquero
- Institut Pasteur, Université Paris Cité, CNRS UMR6047, Archaeal Virology Unit, Paris 75015, France
| | | | - Shengen Shawn Hu
- Department of Biochemistry and Molecular Genetics, University of Virginia School of Medicine, Charlottesville, VA 22903, USA
| | - Jessie Lynda Fields
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, AL 35233, USA
| | - Xing Liu
- Fujian Provincial Key Laboratory of Soil Environmental Health and Regulation, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou 350002, Fujian, China
| | - Christopher Rensing
- Fujian Provincial Key Laboratory of Soil Environmental Health and Regulation, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou 350002, Fujian, China
| | - Edward H Egelman
- Department of Biochemistry and Molecular Genetics, University of Virginia School of Medicine, Charlottesville, VA 22903, USA.
| | - Mart Krupovic
- Institut Pasteur, Université Paris Cité, CNRS UMR6047, Archaeal Virology Unit, Paris 75015, France.
| | - Fengbin Wang
- Department of Biochemistry and Molecular Genetics, University of Virginia School of Medicine, Charlottesville, VA 22903, USA; Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, AL 35233, USA; O'Neal Comprehensive Cancer Center, University of Alabama at Birmingham, Birmingham, AL 35233, USA.
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Sattley WM, Swingley WD, Burchell BM, Dewey ED, Hayward MK, Renbarger TL, Shaffer KN, Stokes LM, Gurbani SA, Kujawa CM, Nuccio DA, Schladweiler J, Touchman JW, Wang-Otomo ZY, Blankenship RE, Madigan MT. Complete genome of the thermophilic purple sulfur Bacterium Thermochromatium tepidum compared to Allochromatium vinosum and other Chromatiaceae. PHOTOSYNTHESIS RESEARCH 2022; 151:125-142. [PMID: 34669148 DOI: 10.1007/s11120-021-00870-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Accepted: 08/07/2021] [Indexed: 06/13/2023]
Abstract
The complete genome sequence of the thermophilic purple sulfur bacterium Thermochromatium tepidum strain MCT (DSM 3771T) is described and contrasted with that of its mesophilic relative Allochromatium vinosum strain D (DSM 180T) and other Chromatiaceae. The Tch. tepidum genome is a single circular chromosome of 2,958,290 base pairs with no plasmids and is substantially smaller than the genome of Alc. vinosum. The Tch. tepidum genome encodes two forms of RuBisCO and contains nifHDK and several other genes encoding a molybdenum nitrogenase but lacks a gene encoding a protein that assembles the Fe-S cluster required to form a functional nitrogenase molybdenum-iron cofactor, leaving the phototroph phenotypically Nif-. Tch. tepidum contains genes necessary for oxidizing sulfide to sulfate as photosynthetic electron donor but is genetically unequipped to either oxidize thiosulfate as an electron donor or carry out assimilative sulfate reduction, both of which are physiological hallmarks of Alc. vinosum. Also unlike Alc. vinosum, Tch. tepidum is obligately phototrophic and unable to grow chemotrophically in darkness by respiration. Several genes present in the Alc. vinosum genome that are absent from the genome of Tch. tepidum likely contribute to the major physiological differences observed between these related purple sulfur bacteria that inhabit distinct ecological niches.
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Affiliation(s)
- W Matthew Sattley
- Division of Natural Sciences, Indiana Wesleyan University, Marion, IN, 46953, USA.
| | - Wesley D Swingley
- Department of Biological Sciences, Northern Illinois University, Dekalb, IL, 60115, USA
| | - Brad M Burchell
- Division of Natural Sciences, Indiana Wesleyan University, Marion, IN, 46953, USA
| | - Emma D Dewey
- Division of Natural Sciences, Indiana Wesleyan University, Marion, IN, 46953, USA
| | - Mackenzie K Hayward
- Division of Natural Sciences, Indiana Wesleyan University, Marion, IN, 46953, USA
| | - Tara L Renbarger
- Division of Natural Sciences, Indiana Wesleyan University, Marion, IN, 46953, USA
| | - Kathryn N Shaffer
- Division of Natural Sciences, Indiana Wesleyan University, Marion, IN, 46953, USA
| | - Lynn M Stokes
- Division of Natural Sciences, Indiana Wesleyan University, Marion, IN, 46953, USA
| | - Sonja A Gurbani
- Department of Biological Sciences, Northern Illinois University, Dekalb, IL, 60115, USA
| | - Catrina M Kujawa
- Department of Biological Sciences, Northern Illinois University, Dekalb, IL, 60115, USA
| | - D Adam Nuccio
- Department of Biological Sciences, Northern Illinois University, Dekalb, IL, 60115, USA
| | - Jacob Schladweiler
- Department of Biological Sciences, Northern Illinois University, Dekalb, IL, 60115, USA
| | - Jeffrey W Touchman
- School of Life Sciences, Arizona State University, Tempe, AR, 85287, USA
| | | | - Robert E Blankenship
- Departments of Chemistry and Biology, Washington University, St. Louis, MO, 63130, USA
| | - Michael T Madigan
- Department of Microbiology, School of Biological Sciences, Southern Illinois University, Carbondale, IL, 62901, USA
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