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Qi YL, Chen YT, Xie YG, Li YX, Rao YZ, Li MM, Xie QJ, Cao XR, Chen L, Qu YN, Yuan ZX, Xiao ZC, Lu L, Jiao JY, Shu WS, Li WJ, Hedlund BP, Hua ZS. Analysis of nearly 3000 archaeal genomes from terrestrial geothermal springs sheds light on interconnected biogeochemical processes. Nat Commun 2024; 15:4066. [PMID: 38744885 PMCID: PMC11094006 DOI: 10.1038/s41467-024-48498-5] [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: 09/07/2023] [Accepted: 05/02/2024] [Indexed: 05/16/2024] Open
Abstract
Terrestrial geothermal springs are physicochemically diverse and host abundant populations of Archaea. However, the diversity, functionality, and geological influences of these Archaea are not well understood. Here we explore the genomic diversity of Archaea in 152 metagenomes from 48 geothermal springs in Tengchong, China, collected from 2016 to 2021. Our dataset is comprised of 2949 archaeal metagenome-assembled genomes spanning 12 phyla and 392 newly identified species, which increases the known species diversity of Archaea by ~48.6%. The structures and potential functions of the archaeal communities are strongly influenced by temperature and pH, with high-temperature acidic and alkaline springs favoring archaeal abundance over Bacteria. Genome-resolved metagenomics and metatranscriptomics provide insights into the potential ecological niches of these Archaea and their potential roles in carbon, sulfur, nitrogen, and hydrogen metabolism. Furthermore, our findings illustrate the interplay of competition and cooperation among Archaea in biogeochemical cycles, possibly arising from overlapping functional niches and metabolic handoffs. Taken together, our study expands the genomic diversity of Archaea inhabiting geothermal springs and provides a foundation for more incisive study of biogeochemical processes mediated by Archaea in geothermal ecosystems.
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Affiliation(s)
- Yan-Ling Qi
- Chinese Academy of Sciences Key Laboratory of Urban Pollutant Conversion, Department of Environmental Science and Engineering, University of Science and Technology of China, Hefei, 230026, China
| | - Ya-Ting Chen
- Institute for Disaster Management and Reconstruction, Sichuan University-Hong Kong Polytechnic University, Chengdu, 610207, China
| | - Yuan-Guo Xie
- Chinese Academy of Sciences Key Laboratory of Urban Pollutant Conversion, Department of Environmental Science and Engineering, University of Science and Technology of China, Hefei, 230026, China
| | - Yu-Xian Li
- Chinese Academy of Sciences Key Laboratory of Urban Pollutant Conversion, Department of Environmental Science and Engineering, University of Science and Technology of China, Hefei, 230026, China
| | - Yang-Zhi Rao
- Chinese Academy of Sciences Key Laboratory of Urban Pollutant Conversion, Department of Environmental Science and Engineering, University of Science and Technology of China, Hefei, 230026, China
| | - Meng-Meng Li
- State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-Sen University, Guangzhou, 510275, PR China
| | - Qi-Jun Xie
- Chinese Academy of Sciences Key Laboratory of Urban Pollutant Conversion, Department of Environmental Science and Engineering, University of Science and Technology of China, Hefei, 230026, China
| | - Xing-Ru Cao
- Chinese Academy of Sciences Key Laboratory of Urban Pollutant Conversion, Department of Environmental Science and Engineering, University of Science and Technology of China, Hefei, 230026, China
| | - Lei Chen
- Chinese Academy of Sciences Key Laboratory of Urban Pollutant Conversion, Department of Environmental Science and Engineering, University of Science and Technology of China, Hefei, 230026, China
| | - Yan-Ni Qu
- Chinese Academy of Sciences Key Laboratory of Urban Pollutant Conversion, Department of Environmental Science and Engineering, University of Science and Technology of China, Hefei, 230026, China
| | - Zhen-Xuan Yuan
- Chinese Academy of Sciences Key Laboratory of Urban Pollutant Conversion, Department of Environmental Science and Engineering, University of Science and Technology of China, Hefei, 230026, China
| | - Zhi-Chao Xiao
- Chinese Academy of Sciences Key Laboratory of Urban Pollutant Conversion, Department of Environmental Science and Engineering, University of Science and Technology of China, Hefei, 230026, China
| | - Lu Lu
- College of Environmental Science and Engineering, China West Normal University, Nanchong, 637009, China
| | - Jian-Yu Jiao
- State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-Sen University, Guangzhou, 510275, PR China
| | - Wen-Sheng Shu
- School of Life Sciences, South China Normal University, Guangzhou, PR China
| | - Wen-Jun Li
- State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-Sen University, Guangzhou, 510275, PR China.
| | - Brian P Hedlund
- School of Life Sciences, University of Nevada Las Vegas, Las Vegas, NV, 89154, USA.
- Nevada Institute of Personalized Medicine, University of Nevada Las Vegas, Las Vegas, NV, 89154, USA.
| | - Zheng-Shuang Hua
- Chinese Academy of Sciences Key Laboratory of Urban Pollutant Conversion, Department of Environmental Science and Engineering, University of Science and Technology of China, Hefei, 230026, China.
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Liu C, Schmitz RA, Pol A, Hogendoorn C, Verhagen D, Peeters SH, van Alen TA, Cremers G, Mesman RA, Op den Camp HJM. Active coexistence of the novel gammaproteobacterial methanotroph 'Ca. Methylocalor cossyra' CH1 and verrucomicrobial methanotrophs in acidic, hot geothermal soil. Environ Microbiol 2024; 26:e16602. [PMID: 38454738 DOI: 10.1111/1462-2920.16602] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2023] [Accepted: 02/16/2024] [Indexed: 03/09/2024]
Abstract
Terrestrial geothermal ecosystems are hostile habitats, characterized by large emissions of environmentally relevant gases such as CO2 , CH4 , H2 S and H2 . These conditions provide a niche for chemolithoautotrophic microorganisms. Methanotrophs of the phylum Verrucomicrobia, which inhabit these ecosystems, can utilize these gases and grow at pH levels below 1 and temperatures up to 65°C. In contrast, methanotrophs of the phylum Proteobacteria are primarily found in various moderate environments. Previously, novel verrucomicrobial methanotrophs were detected and isolated from the geothermal soil of the Favara Grande on the island of Pantelleria, Italy. The detection of pmoA genes, specific for verrucomicrobial and proteobacterial methanotrophs in this environment, and the partially overlapping pH and temperature growth ranges of these isolates suggest that these distinct phylogenetic groups could coexist in the environment. In this report, we present the isolation and characterization of a thermophilic and acid-tolerant gammaproteobacterial methanotroph (family Methylococcaceae) from the Favara Grande. This isolate grows at pH values ranging from 3.5 to 7.0 and temperatures from 35°C to 55°C, and diazotrophic growth was demonstrated. Its genome contains genes encoding particulate and soluble methane monooxygenases, XoxF- and MxaFI-type methanol dehydrogenases, and all enzymes of the Calvin cycle. For this novel genus and species, we propose the name 'Candidatus Methylocalor cossyra' CH1.
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Affiliation(s)
- Changqing Liu
- Department of Microbiology, Faculty of Science, Radboud Institute for Biological and Environmental Sciences, Radboud University Nijmegen, Nijmegen, the Netherlands
| | - Rob A Schmitz
- Department of Microbiology, Faculty of Science, Radboud Institute for Biological and Environmental Sciences, Radboud University Nijmegen, Nijmegen, the Netherlands
| | - Arjan Pol
- Department of Microbiology, Faculty of Science, Radboud Institute for Biological and Environmental Sciences, Radboud University Nijmegen, Nijmegen, the Netherlands
| | - Carmen Hogendoorn
- Department of Microbiology, Faculty of Science, Radboud Institute for Biological and Environmental Sciences, Radboud University Nijmegen, Nijmegen, the Netherlands
| | - Daniël Verhagen
- Department of Microbiology, Faculty of Science, Radboud Institute for Biological and Environmental Sciences, Radboud University Nijmegen, Nijmegen, the Netherlands
| | - Stijn H Peeters
- Department of Microbiology, Faculty of Science, Radboud Institute for Biological and Environmental Sciences, Radboud University Nijmegen, Nijmegen, the Netherlands
| | - Theo A van Alen
- Department of Microbiology, Faculty of Science, Radboud Institute for Biological and Environmental Sciences, Radboud University Nijmegen, Nijmegen, the Netherlands
| | - Geert Cremers
- Department of Microbiology, Faculty of Science, Radboud Institute for Biological and Environmental Sciences, Radboud University Nijmegen, Nijmegen, the Netherlands
| | - Rob A Mesman
- Department of Microbiology, Faculty of Science, Radboud Institute for Biological and Environmental Sciences, Radboud University Nijmegen, Nijmegen, the Netherlands
| | - Huub J M Op den Camp
- Department of Microbiology, Faculty of Science, Radboud Institute for Biological and Environmental Sciences, Radboud University Nijmegen, Nijmegen, the Netherlands
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3
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Kop LFM, Koch H, Jetten MSM, Daims H, Lücker S. Metabolic and phylogenetic diversity in the phylum Nitrospinota revealed by comparative genome analyses. ISME COMMUNICATIONS 2024; 4:ycad017. [PMID: 38317822 PMCID: PMC10839748 DOI: 10.1093/ismeco/ycad017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/07/2023] [Revised: 12/22/2023] [Accepted: 12/22/2023] [Indexed: 02/07/2024]
Abstract
The most abundant known nitrite-oxidizing bacteria in the marine water column belong to the phylum Nitrospinota. Despite their importance in marine nitrogen cycling and primary production, there are only few cultured representatives that all belong to the class Nitrospinia. Moreover, although Nitrospinota were traditionally thought to be restricted to marine environments, metagenome-assembled genomes have also been recovered from groundwater. Over the recent years, metagenomic sequencing has led to the discovery of several novel classes of Nitrospinota (UBA9942, UBA7883, 2-12-FULL-45-22, JACRGO01, JADGAW01), which remain uncultivated and have not been analyzed in detail. Here, we analyzed a nonredundant set of 98 Nitrospinota genomes with focus on these understudied Nitrospinota classes and compared their metabolic profiles to get insights into their potential role in biogeochemical element cycling. Based on phylogenomic analysis and average amino acid identities, the highly diverse phylum Nitrospinota could be divided into at least 33 different genera, partly with quite distinct metabolic capacities. Our analysis shows that not all Nitrospinota are nitrite oxidizers and that members of this phylum have the genomic potential to use sulfide and hydrogen for energy conservation. This study expands our knowledge of the phylogeny and potential ecophysiology of the phylum Nitrospinota and offers new avenues for the isolation and cultivation of these elusive bacteria.
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Affiliation(s)
- Linnea F M Kop
- Department of Microbiology, Radboud Institute for Biological and Environmental Sciences, Radboud University, Heyendaalseweg 135, Nijmegen 6525 AJ, The Netherlands
- Division of Microbial Ecology, Centre for Microbiology and Environmental Systems Science, University of Vienna, Djerassiplatz 1, Vienna 1030, Austria
| | - Hanna Koch
- Department of Microbiology, Radboud Institute for Biological and Environmental Sciences, Radboud University, Heyendaalseweg 135, Nijmegen 6525 AJ, The Netherlands
- Bioresources Unit, Center for Health & Bioresources, AIT Austrian Institute of Technology GmbH, Konrad-Lorenz-Straße 24, Tulln an der Donau 3430, Austria
| | - Mike S M Jetten
- Department of Microbiology, Radboud Institute for Biological and Environmental Sciences, Radboud University, Heyendaalseweg 135, Nijmegen 6525 AJ, The Netherlands
| | - Holger Daims
- Division of Microbial Ecology, Centre for Microbiology and Environmental Systems Science, University of Vienna, Djerassiplatz 1, Vienna 1030, Austria
| | - Sebastian Lücker
- Department of Microbiology, Radboud Institute for Biological and Environmental Sciences, Radboud University, Heyendaalseweg 135, Nijmegen 6525 AJ, The Netherlands
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Leone L, Sgueglia G, La Gatta S, Chino M, Nastri F, Lombardi A. Enzymatic and Bioinspired Systems for Hydrogen Production. Int J Mol Sci 2023; 24:ijms24108605. [PMID: 37239950 DOI: 10.3390/ijms24108605] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2023] [Revised: 04/30/2023] [Accepted: 05/08/2023] [Indexed: 05/28/2023] Open
Abstract
The extraordinary potential of hydrogen as a clean and sustainable fuel has sparked the interest of the scientific community to find environmentally friendly methods for its production. Biological catalysts are the most attractive solution, as they usually operate under mild conditions and do not produce carbon-containing byproducts. Hydrogenases promote reversible proton reduction to hydrogen in a variety of anoxic bacteria and algae, displaying unparallel catalytic performances. Attempts to use these sophisticated enzymes in scalable hydrogen production have been hampered by limitations associated with their production and stability. Inspired by nature, significant efforts have been made in the development of artificial systems able to promote the hydrogen evolution reaction, via either electrochemical or light-driven catalysis. Starting from small-molecule coordination compounds, peptide- and protein-based architectures have been constructed around the catalytic center with the aim of reproducing hydrogenase function into robust, efficient, and cost-effective catalysts. In this review, we first provide an overview of the structural and functional properties of hydrogenases, along with their integration in devices for hydrogen and energy production. Then, we describe the most recent advances in the development of homogeneous hydrogen evolution catalysts envisioned to mimic hydrogenases.
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Affiliation(s)
- Linda Leone
- Department of Chemical Sciences, University of Naples Federico II, 80126 Naples, Italy
| | - Gianmattia Sgueglia
- Department of Chemical Sciences, University of Naples Federico II, 80126 Naples, Italy
| | - Salvatore La Gatta
- Department of Chemical Sciences, University of Naples Federico II, 80126 Naples, Italy
| | - Marco Chino
- Department of Chemical Sciences, University of Naples Federico II, 80126 Naples, Italy
| | - Flavia Nastri
- Department of Chemical Sciences, University of Naples Federico II, 80126 Naples, Italy
| | - Angela Lombardi
- Department of Chemical Sciences, University of Naples Federico II, 80126 Naples, Italy
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5
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Ortiz-Medina JF, Poole MR, Grunden AM, Call DF. Nitrogen Fixation and Ammonium Assimilation Pathway Expression of Geobacter sulfurreducens Changes in Response to the Anode Potential in Microbial Electrochemical Cells. Appl Environ Microbiol 2023; 89:e0207322. [PMID: 36975810 PMCID: PMC10132095 DOI: 10.1128/aem.02073-22] [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: 12/07/2022] [Accepted: 03/07/2023] [Indexed: 03/29/2023] Open
Abstract
Nitrogen gas (N2) fixation in the anode-respiring bacterium Geobacter sulfurreducens occurs through complex, multistep processes. Optimizing ammonium (NH4+) production from this bacterium in microbial electrochemical technologies (METs) requires an understanding of how those processes are regulated in response to electrical driving forces. In this study, we quantified gene expression levels (via RNA sequencing) of G. sulfurreducens growing on anodes fixed at two different potentials (-0.15 V and +0.15 V versus standard hydrogen electrode). The anode potential had a significant impact on the expression levels of N2 fixation genes. At -0.15 V, the expression of nitrogenase genes, such as nifH, nifD, and nifK, significantly increased relative to that at +0.15 V, as well as genes associated with NH4+ uptake and transformation, such as glutamine and glutamate synthetases. Metabolite analysis confirmed that both of these organic compounds were present in significantly higher intracellular concentrations at -0.15 V. N2 fixation rates (estimated using the acetylene reduction assay and normalized to total protein) were significantly larger at -0.15 V. Genes expressing flavin-based electron bifurcation complexes, such as electron-transferring flavoproteins (EtfAB) and the NADH-dependent ferredoxin:NADP reductase (NfnAB), were also significantly upregulated at -0.15 V, suggesting that these mechanisms may be involved in N2 fixation at that potential. Our results show that in energy-constrained situations (i.e., low anode potential), the cells increase per-cell respiration and N2 fixation rates. We hypothesize that at -0.15 V, they increase N2 fixation activity to help maintain redox homeostasis, and they leverage electron bifurcation as a strategy to optimize energy generation and use. IMPORTANCE Biological nitrogen fixation coupled with ammonium recovery provides a sustainable alternative to the carbon-, water-, and energy-intensive Haber-Bosch process. Aerobic biological nitrogen fixation technologies are hindered by oxygen gas inhibition of the nitrogenase enzyme. Electrically driving biological nitrogen fixation in anaerobic microbial electrochemical technologies overcomes this challenge. Using Geobacter sulfurreducens as a model exoelectrogenic diazotroph, we show that the anode potential in microbial electrochemical technologies has a significant impact on nitrogen gas fixation rates, ammonium assimilation pathways, and expression of genes associated with nitrogen gas fixation. These findings have important implications for understanding regulatory pathways of nitrogen gas fixation and will help identify target genes and operational strategies to enhance ammonium production in microbial electrochemical technologies.
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Affiliation(s)
- Juan F. Ortiz-Medina
- Department of Civil, Construction, and Environmental Engineering, North Carolina State University, Raleigh, North Carolina, USA
| | - Mark R. Poole
- Department of Civil, Construction, and Environmental Engineering, North Carolina State University, Raleigh, North Carolina, USA
| | - Amy M. Grunden
- Department of Plant and Microbial Biology, North Carolina State University, Raleigh, North Carolina, USA
| | - Douglas F. Call
- Department of Civil, Construction, and Environmental Engineering, North Carolina State University, Raleigh, North Carolina, USA
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Garg S, Mishra V, Vega LF, Sharma RS, Dumée LF. Hydrogen Biosensing: Prospects, Parallels, and Challenges. Ind Eng Chem Res 2023. [DOI: 10.1021/acs.iecr.2c03965] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Affiliation(s)
- Shafali Garg
- Department of Environmental Studies, Bioresources and Environmental Biotechnology Laboratory, University of Delhi, Delhi110007, India
| | - Vandana Mishra
- Department of Environmental Studies, Bioresources and Environmental Biotechnology Laboratory, University of Delhi, Delhi110007, India
- Centre for Inter-disciplinary Studies of Mountain & Hill Environment (CISMHE), University of Delhi, Delhi110007, India
- Delhi School of Climate Change and Sustainability, Institute of Eminence, University of Delhi, Delhi110007, India
| | - Lourdes F. Vega
- Khalifa University, Department of Chemical Engineering, Abu Dhabi127788, United Arab Emirates
- Khalifa University, Research, and Innovation Center on CO2 and Hydrogen, Abu Dhabi127788, United Arab Emirates
| | - Radhey Shyam Sharma
- Department of Environmental Studies, Bioresources and Environmental Biotechnology Laboratory, University of Delhi, Delhi110007, India
- Centre for Inter-disciplinary Studies of Mountain & Hill Environment (CISMHE), University of Delhi, Delhi110007, India
- Delhi School of Climate Change and Sustainability, Institute of Eminence, University of Delhi, Delhi110007, India
| | - Ludovic F. Dumée
- Khalifa University, Department of Chemical Engineering, Abu Dhabi127788, United Arab Emirates
- Khalifa University, Research, and Innovation Center on CO2 and Hydrogen, Abu Dhabi127788, United Arab Emirates
- Khalifa University, Center for Membrane and Advanced Water Technology, Abu Dhabi127788, United Arab Emirates
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Slobodkina G, Ratnikova N, Merkel A, Kevbrin V, Kuchierskaya A, Slobodkin A. Lithoautotrophic lifestyle of the widespread genus Roseovarius revealed by physiological and genomic characterization of Roseovarius autotrophicus sp. nov. FEMS Microbiol Ecol 2022; 98:6724241. [PMID: 36166357 DOI: 10.1093/femsec/fiac113] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2022] [Revised: 07/13/2022] [Accepted: 09/23/2022] [Indexed: 12/14/2022] Open
Abstract
The genus Roseovarius, a member of the ecologically important Roseobacter-clade, is widespread throughout the world. A facultatively anaerobic lithoautotrophic bacterium (strain SHN287T), belonging to the genus Roseovarius, was isolated with molecular hydrogen as an electron donor and nitrate as an electron acceptor from a terrestrial mud volcano. Strain SHN287T possessed metabolic features not reported for Roseovarius such as chemolithoautotrophic growth with oxidation of molecular hydrogen or sulfur compounds, anaerobic growth and denitrification. Based on the phenotypic and phylogenetic characteristics, the new isolate is considered to represent a novel species of the genus Roseovarius, for which the name Roseovarius autotrophicus sp. nov. is proposed. The type strain is SHN287T (= KCTC 15916T = VKM B-3404T). An amended description of the genus Roseovarius is provided. Comparison of 46 Roseovarius genomes revealed that (i) a full set of genes for the Calvin-Benson cycle is present only in two strains: SHN287T and Roseovarius salinarum; (ii) respiratory H2-uptake [NiFe] hydrogenases are specific for a phylogenetically distinct group, including SHN287T-related strains; (iii) the Sox enzymatic complex is encoded in most of the studied genomes; and (iv) denitrification genes are widespread and randomly distributed among the genus. The metabolic characteristics found in R. autotrophicus sp. nov. expand the ecological role of the genus Roseovarius.
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Affiliation(s)
- Galina Slobodkina
- Winogradsky Institute of Microbiology, FRC Biotechnology Russian Academy of Sciences, Leninskiy Prospect, 33, bld. 2, 119071, Moscow, Russia
| | - Nataliya Ratnikova
- Winogradsky Institute of Microbiology, FRC Biotechnology Russian Academy of Sciences, Leninskiy Prospect, 33, bld. 2, 119071, Moscow, Russia
| | - Alexander Merkel
- Winogradsky Institute of Microbiology, FRC Biotechnology Russian Academy of Sciences, Leninskiy Prospect, 33, bld. 2, 119071, Moscow, Russia
| | - Vadim Kevbrin
- Winogradsky Institute of Microbiology, FRC Biotechnology Russian Academy of Sciences, Leninskiy Prospect, 33, bld. 2, 119071, Moscow, Russia
| | | | - Alexander Slobodkin
- Winogradsky Institute of Microbiology, FRC Biotechnology Russian Academy of Sciences, Leninskiy Prospect, 33, bld. 2, 119071, Moscow, Russia
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8
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Candidatus Eremiobacterota, a metabolically and phylogenetically diverse terrestrial phylum with acid-tolerant adaptations. THE ISME JOURNAL 2021; 15:2692-2707. [PMID: 33753881 PMCID: PMC8397712 DOI: 10.1038/s41396-021-00944-8] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/20/2020] [Revised: 02/11/2021] [Accepted: 02/18/2021] [Indexed: 02/01/2023]
Abstract
Candidatus phylum Eremiobacterota (formerly WPS-2) is an as-yet-uncultured bacterial clade that takes its name from Ca. Eremiobacter, an Antarctic soil aerobe proposed to be capable of a novel form of chemolithoautotrophy termed atmospheric chemosynthesis, that uses the energy derived from atmospheric H2-oxidation to fix CO2 through the Calvin-Benson-Bassham (CBB) cycle via type 1E RuBisCO. To elucidate the phylogenetic affiliation and metabolic capacities of Ca. Eremiobacterota, we analysed 63 public metagenome-assembled genomes (MAGs) and nine new MAGs generated from Antarctic soil metagenomes. These MAGs represent both recognized classes within Ca. Eremiobacterota, namely Ca. Eremiobacteria and UBP9. Ca. Eremiobacteria are inferred to be facultatively acidophilic with a preference for peptides and amino acids as nutrient sources. Epifluorescence microscopy revealed Ca. Eremiobacteria cells from Antarctica desert soil to be coccoid in shape. Two orders are recognized within class Ca. Eremiobacteria: Ca. Eremiobacterales and Ca. Baltobacterales. The latter are metabolically versatile, with individual members having genes required for trace gas driven autotrophy, anoxygenic photosynthesis, CO oxidation, and anaerobic respiration. UBP9, here renamed Ca. Xenobia class. nov., are inferred to be obligate heterotrophs with acidophilic adaptations, but individual members having highly divergent metabolic capacities compared to Ca. Eremiobacteria, especially with regard to respiration and central carbon metabolism. We conclude Ca. Eremiobacterota to be an ecologically versatile phylum with the potential to thrive under an array of "extreme" environmental conditions.
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9
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Montgomery K, Williams TJ, Brettle M, Berengut JF, Zhang E, Zaugg J, Hugenholtz P, Ferrari BC. Persistence and resistance: survival mechanisms of Candidatus Dormibacterota from nutrient-poor Antarctic soils. Environ Microbiol 2021; 23:4276-4294. [PMID: 34029441 DOI: 10.1111/1462-2920.15610] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2021] [Revised: 05/18/2021] [Accepted: 05/19/2021] [Indexed: 11/28/2022]
Abstract
Candidatus Dormibacterota is an uncultured bacterial phylum found predominantly in soil that is present in high abundances within cold desert soils. Here, we interrogate nine metagenome-assembled genomes (MAGs), including six new MAGs derived from soil metagenomes obtained from two eastern Antarctic sites. Phylogenomic and taxonomic analyses revealed these MAGs represent four genera and five species, representing two order-level clades within Ca. Dormibacterota. Metabolic reconstructions of these MAGs revealed the potential for aerobic metabolism, and versatile adaptations enabling persistence in the 'extreme' Antarctic environment. Primary amongst these adaptations were abilities to scavenge atmospheric H2 and CO as energy sources, as well as using the energy derived from H2 oxidation to fix atmospheric CO2 via the Calvin-Bassham-Benson cycle, using a RuBisCO type IE. We propose that these allow Ca. Dormibacterota to persist using H2 oxidation and grow using atmospheric chemosynthesis in terrestrial Antarctica. Fluorescence in situ hybridization revealed Ca. Dormibacterota to be coccoid cells, 0.3-1.4 μm in diameter, with some cells exhibiting the potential for a symbiotic or syntrophic lifestyle.
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Affiliation(s)
- Kate Montgomery
- School of Biotechnology and Biomolecular Sciences, UNSW Sydney, Randwick, NSW, 2052, Australia
| | - Timothy J Williams
- School of Biotechnology and Biomolecular Sciences, UNSW Sydney, Randwick, NSW, 2052, Australia
| | - Merryn Brettle
- Biomedical Imaging Facility, Mark Wainwright Analytical Centre, UNSW Sydney, Randwick, NSW, 2052, Australia
| | - Jonathan F Berengut
- EMBL Australia Node for Single Molecule Science, School of Medical Sciences, UNSW Sydney, Kensington, NSW, 2052, Australia
| | - Eden Zhang
- School of Biotechnology and Biomolecular Sciences, UNSW Sydney, Randwick, NSW, 2052, Australia
| | - Julian Zaugg
- Australian Centre for Ecogenomics, School of Chemistry and Molecular Biosciences, The University of Queensland, St Lucia, Qld, 4072, Australia
| | - Philip Hugenholtz
- Australian Centre for Ecogenomics, School of Chemistry and Molecular Biosciences, The University of Queensland, St Lucia, Qld, 4072, Australia
| | - Belinda C Ferrari
- School of Biotechnology and Biomolecular Sciences, UNSW Sydney, Randwick, NSW, 2052, Australia
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Li Z, Gu J, Ding J, Ren N, Xing D. Molecular mechanism of ethanol-H 2 co-production fermentation in anaerobic acidogenesis: Challenges and perspectives. Biotechnol Adv 2020; 46:107679. [PMID: 33316366 DOI: 10.1016/j.biotechadv.2020.107679] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2020] [Revised: 12/04/2020] [Accepted: 12/07/2020] [Indexed: 12/29/2022]
Abstract
Ethanol-type fermentation (ETF) is one of three fermentation types during the acidogenesis of the anaerobic biological treatment. Ethanoligenens, a representative genus of ETF, displays acidophilic, autoaggregative, and ethanol-H2 co-producing characteristics and facilitates subsequent methanogenesis. Here, the latest advances in the molecular mechanisms of the metabolic regulation of ethanol-H2 co-producing bacteria based on multi-omics studies were comprehensively reviewed. Comparative genomics demonstrated a low genetic similarity between Ethanoligenens and other hydrogen-producing genera. FeFe‑hydrogenases (FeFe-H2ases) and pyruvate ferredoxin oxidoreductase (PFOR) played critical roles in the ethanol-H2 co-metabolic pathway of Ethanoligenens. Global transcriptome analysis revealed that highly expressed [FeFe]-H2ases and ferredoxins drove hydrogen production by Ethanoligenens at low pH conditions (4.0-4.5). Quantitative proteomic analysis also proved that this genus resists acetic acid-induced intracellular acidification through the up-regulated expression of pyrimidine metabolism related proteins. The autoaggregation of Ethanoligenen facilitated its granulation with acetate-oxidizing bacteria in co-culture systems and mitigated a fast pH drop, providing a new approach for solving a pH imbalance and improving hydrogen production. In-depth studies of the regulatory mechanism underlying ethanol-H2 co-production metabolism and the syntrophic interactions of ethanol-H2 co-producing Ethanoligenens with other microorganisms will provide insights into the improvement of bioenergy recovery in anaerobic biotechnology. The coupling of ETF with other biotechnologies, which based on the regulation of electron flow direction, syntrophic interaction, and metabolic flux, can be potential strategies to enhance the cascade recovery of energy and resources.
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Affiliation(s)
- Zhen Li
- State Key Laboratory of Urban Water Resource and Environment, School of Environment, Harbin Institute of Technology, Harbin 150090, China
| | - Jiayu Gu
- State Key Laboratory of Urban Water Resource and Environment, School of Environment, Harbin Institute of Technology, Harbin 150090, China
| | - Jie Ding
- State Key Laboratory of Urban Water Resource and Environment, School of Environment, Harbin Institute of Technology, Harbin 150090, China
| | - Nanqi Ren
- State Key Laboratory of Urban Water Resource and Environment, School of Environment, Harbin Institute of Technology, Harbin 150090, China
| | - Defeng Xing
- State Key Laboratory of Urban Water Resource and Environment, School of Environment, Harbin Institute of Technology, Harbin 150090, China.
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11
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Abstract
Volcanic and geothermal environments are characterized by low pH, high temperatures, and gas emissions consisting of mainly CO2 and varied CH4, H2S, and H2 contents which allow the formation of chemolithoautotrophic microbial communities. To determine the link between the emitted gases and the microbial community composition, geochemical and metagenomic analysis were performed. Soil samples of the geothermic region Favara Grande (Pantelleria, Italy) were taken at various depths (1 to 50 cm). Analysis of the gas composition revealed that CH4 and H2 have the potential to serve as the driving forces for the microbial community. Our metagenomic analysis revealed a high relative abundance of Bacteria in the top layer (1 to 10 cm), but the relative abundance of Archaea increased with depth from 32% to 70%. In particular, a putative hydrogenotrophic methanogenic archaeon, related to Methanocella conradii, appeared to have a high relative abundance (63%) in deeper layers. A variety of [NiFe]-hydrogenase genes were detected, showing that H2 was an important electron donor for microaerobic microorganisms in the upper layers. Furthermore, the bacterial population included verrucomicrobial and proteobacterial methanotrophs, the former showing an up to 7.8 times higher relative abundance. Analysis of the metabolic potential of this microbial community showed a clear capacity to oxidize CH4 aerobically, as several genes for distinct particulate methane monooxygenases and lanthanide-dependent methanol dehydrogenases (XoxF-type) were retrieved. Analysis of the CO2 fixation pathways showed the presence of the Calvin-Benson-Bassham cycle, the Wood-Ljungdahl pathway, and the (reverse) tricarboxylic acid (TCA) cycle, the latter being the most represented carbon fixation pathway. This study indicates that the methane emissions in the Favara Grande might be a combination of geothermal activity and biological processes and further provides insights into the diversity of the microbial population thriving on CH4 and H2 IMPORTANCE The Favara Grande nature reserve on the volcanic island of Pantelleria (Italy) is known for its geothermal gas emissions and high soil temperatures. These volcanic soil ecosystems represent "hot spots" of greenhouse gas emissions. The unique community might be shaped by the hostile conditions in the ecosystem, and it is involved in the cycling of elements such as carbon, hydrogen, sulfur, and nitrogen. Our metagenome study revealed that most of the microorganisms in this extreme environment are only distantly related to cultivated bacteria. The results obtained profoundly increased the understanding of these natural hot spots of greenhouse gas production/degradation and will help to enrich and isolate the microbial key players. After isolation, it will become possible to unravel the molecular mechanisms by which they adapt to extreme (thermo/acidophilic) conditions, and this may lead to new green enzymatic catalysts and technologies for industry.
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Hakobyan A, Zhu J, Glatter T, Paczia N, Liesack W. Hydrogen utilization by Methylocystis sp. strain SC2 expands the known metabolic versatility of type IIa methanotrophs. Metab Eng 2020; 61:181-196. [PMID: 32479801 DOI: 10.1016/j.ymben.2020.05.003] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2019] [Revised: 03/20/2020] [Accepted: 05/01/2020] [Indexed: 12/19/2022]
Abstract
Methane, a non-expensive natural substrate, is used by Methylocystis spp. as a sole source of carbon and energy. Here, we assessed whether Methylocystis sp. strain SC2 is able to also utilize hydrogen as an energy source. The addition of 2% H2 to the culture headspace had the most significant positive effect on the growth yield under CH4 (6%) and O2 (3%) limited conditions. The SC2 biomass yield doubled from 6.41 (±0.52) to 13.82 (±0.69) mg cell dry weight per mmol CH4, while CH4 consumption was significantly reduced. Regardless of H2 addition, CH4 utilization was increasingly redirected from respiration to fermentation-based pathways with decreasing O2/CH4 mixing ratios. Theoretical thermodynamic calculations confirmed that hydrogen utilization under oxygen-limited conditions doubles the maximum biomass yield compared to fully aerobic conditions without H2 addition. Hydrogen utilization was linked to significant changes in the SC2 proteome. In addition to hydrogenase accessory proteins, the production of Group 1d and Group 2b hydrogenases was significantly increased in both short- and long-term incubations. Both long-term incubation with H2 (37 d) and treatments with chemical inhibitors revealed that SC2 growth under hydrogen-utilizing conditions does not require the activity of complex I. Apparently, strain SC2 has the metabolic capacity to channel hydrogen-derived electrons into the quinone pool, which provides a link between hydrogen oxidation and energy production. In summary, H2 may be a promising alternative energy source in biotechnologically oriented methanotroph projects that aim to maximize biomass yield from CH4, such as the production of high-quality feed protein.
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Affiliation(s)
- Anna Hakobyan
- Research Group "Methanotrophic Bacteria and Environmental Genomics/Transcriptomics", Max Planck Institute for Terrestrial Microbiology, Marburg, Germany
| | - Jing Zhu
- Research Group "Methanotrophic Bacteria and Environmental Genomics/Transcriptomics", Max Planck Institute for Terrestrial Microbiology, Marburg, Germany; Institute of Environmental Science and Technology, Zhejiang University, Hangzhou, China
| | - Timo Glatter
- Core Facility for Mass Spectrometry and Proteomics, Max Planck Institute for Terrestrial Microbiology, Marburg, Germany
| | - Nicole Paczia
- Core Facility for Metabolomics and Small Molecule Mass Spectrometry, Max Planck Institute for Terrestrial Microbiology, Marburg, Germany
| | - Werner Liesack
- Research Group "Methanotrophic Bacteria and Environmental Genomics/Transcriptomics", Max Planck Institute for Terrestrial Microbiology, Marburg, Germany; Center for Synthetic Microbiology (SYNMIKRO), Philipps-Universität Marburg, Marburg, Germany.
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13
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Benoit SL, Maier RJ, Sawers RG, Greening C. Molecular Hydrogen Metabolism: a Widespread Trait of Pathogenic Bacteria and Protists. Microbiol Mol Biol Rev 2020; 84:e00092-19. [PMID: 31996394 PMCID: PMC7167206 DOI: 10.1128/mmbr.00092-19] [Citation(s) in RCA: 51] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Pathogenic microorganisms use various mechanisms to conserve energy in host tissues and environmental reservoirs. One widespread but often overlooked means of energy conservation is through the consumption or production of molecular hydrogen (H2). Here, we comprehensively review the distribution, biochemistry, and physiology of H2 metabolism in pathogens. Over 200 pathogens and pathobionts carry genes for hydrogenases, the enzymes responsible for H2 oxidation and/or production. Furthermore, at least 46 of these species have been experimentally shown to consume or produce H2 Several major human pathogens use the large amounts of H2 produced by colonic microbiota as an energy source for aerobic or anaerobic respiration. This process has been shown to be critical for growth and virulence of the gastrointestinal bacteria Salmonella enterica serovar Typhimurium, Campylobacter jejuni, Campylobacter concisus, and Helicobacter pylori (including carcinogenic strains). H2 oxidation is generally a facultative trait controlled by central regulators in response to energy and oxidant availability. Other bacterial and protist pathogens produce H2 as a diffusible end product of fermentation processes. These include facultative anaerobes such as Escherichia coli, S Typhimurium, and Giardia intestinalis, which persist by fermentation when limited for respiratory electron acceptors, as well as obligate anaerobes, such as Clostridium perfringens, Clostridioides difficile, and Trichomonas vaginalis, that produce large amounts of H2 during growth. Overall, there is a rich literature on hydrogenases in growth, survival, and virulence in some pathogens. However, we lack a detailed understanding of H2 metabolism in most pathogens, especially obligately anaerobic bacteria, as well as a holistic understanding of gastrointestinal H2 transactions overall. Based on these findings, we also evaluate H2 metabolism as a possible target for drug development or other therapies.
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Affiliation(s)
- Stéphane L Benoit
- Department of Microbiology, University of Georgia, Athens, Georgia, USA
| | - Robert J Maier
- Department of Microbiology, University of Georgia, Athens, Georgia, USA
| | - R Gary Sawers
- Institute of Microbiology, Martin Luther University Halle-Wittenberg, Halle, Germany
| | - Chris Greening
- School of Biological Sciences, Monash University, Clayton, VIC, Australia
- Department of Microbiology, Monash Biomedicine Discovery Institute, Clayton, VIC, Australia
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14
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Schmitz RA, Pol A, Mohammadi SS, Hogendoorn C, van Gelder AH, Jetten MSM, Daumann LJ, Op den Camp HJM. The thermoacidophilic methanotroph Methylacidiphilum fumariolicum SolV oxidizes subatmospheric H 2 with a high-affinity, membrane-associated [NiFe] hydrogenase. ISME JOURNAL 2020; 14:1223-1232. [PMID: 32042101 PMCID: PMC7174314 DOI: 10.1038/s41396-020-0609-3] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/19/2019] [Revised: 01/28/2020] [Accepted: 01/30/2020] [Indexed: 12/23/2022]
Abstract
The trace amounts (0.53 ppmv) of atmospheric hydrogen gas (H2) can be utilized by microorganisms to persist during dormancy. This process is catalyzed by certain Actinobacteria, Acidobacteria, and Chloroflexi, and is estimated to convert 75 × 1012 g H2 annually, which is half of the total atmospheric H2. This rapid atmospheric H2 turnover is hypothesized to be catalyzed by high-affinity [NiFe] hydrogenases. However, apparent high-affinity H2 oxidation has only been shown in whole cells, rather than for the purified enzyme. Here, we show that the membrane-associated hydrogenase from the thermoacidophilic methanotroph Methylacidiphilum fumariolicum SolV possesses a high apparent affinity (Km(app) = 140 nM) for H2 and that methanotrophs can oxidize subatmospheric H2. Our findings add to the evidence that the group 1h [NiFe] hydrogenase is accountable for atmospheric H2 oxidation and that it therefore could be a strong controlling factor in the global H2 cycle. We show that the isolated enzyme possesses a lower affinity (Km = 300 nM) for H2 than the membrane-associated enzyme. Hence, the membrane association seems essential for a high affinity for H2. The enzyme is extremely thermostable and remains folded up to 95 °C. Strain SolV is the only known organism in which the group 1h [NiFe] hydrogenase is responsible for rapid growth on H2 as sole energy source as well as oxidation of subatmospheric H2. The ability to conserve energy from H2 could increase fitness of verrucomicrobial methanotrophs in geothermal ecosystems with varying CH4 fluxes. We propose that H2 oxidation can enhance growth of methanotrophs in aerated methane-driven ecosystems. Group 1h [NiFe] hydrogenases could therefore contribute to mitigation of global warming, since CH4 is an important and extremely potent greenhouse gas.
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Affiliation(s)
- Rob A Schmitz
- Department of Microbiology, Radboud University, Heyendaalseweg 135, NL-6525 AJ, Nijmegen, The Netherlands
| | - Arjan Pol
- Department of Microbiology, Radboud University, Heyendaalseweg 135, NL-6525 AJ, Nijmegen, The Netherlands
| | - Sepehr S Mohammadi
- Department of Microbiology, Radboud University, Heyendaalseweg 135, NL-6525 AJ, Nijmegen, The Netherlands
| | - Carmen Hogendoorn
- Department of Microbiology, Radboud University, Heyendaalseweg 135, NL-6525 AJ, Nijmegen, The Netherlands
| | - Antonie H van Gelder
- Laboratory of Microbiology, Wageningen University and Research, Stippeneng 4, 6708 WE, Wageningen, The Netherlands
| | - Mike S M Jetten
- Department of Microbiology, Radboud University, Heyendaalseweg 135, NL-6525 AJ, Nijmegen, The Netherlands
| | - Lena J Daumann
- Department Chemie, Ludwig-Maximilians-Universität München, Butenandtstraβe 5-13, D-81377, München, Germany
| | - Huub J M Op den Camp
- Department of Microbiology, Radboud University, Heyendaalseweg 135, NL-6525 AJ, Nijmegen, The Netherlands.
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15
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Greening C, Boyd E. Editorial: Microbial Hydrogen Metabolism. Front Microbiol 2020; 11:56. [PMID: 32082284 PMCID: PMC7002543 DOI: 10.3389/fmicb.2020.00056] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2019] [Accepted: 01/13/2020] [Indexed: 11/14/2022] Open
Affiliation(s)
- Chris Greening
- School of Biological Sciences, Monash University, Clayton, VIC, Australia
| | - Eric Boyd
- Department of Microbiology and Immunology, Montana State University, Bozeman, MT, United States
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16
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Salina EG, Grigorov A, Skvortsova Y, Majorov K, Bychenko O, Ostrik A, Logunova N, Ignatov D, Kaprelyants A, Apt A, Azhikina T. MTS1338, A Small Mycobacterium tuberculosis RNA, Regulates Transcriptional Shifts Consistent With Bacterial Adaptation for Entering Into Dormancy and Survival Within Host Macrophages. Front Cell Infect Microbiol 2019; 9:405. [PMID: 31850238 PMCID: PMC6901956 DOI: 10.3389/fcimb.2019.00405] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2019] [Accepted: 11/12/2019] [Indexed: 11/13/2022] Open
Abstract
Small non-coding RNAs play a significant role in bacterial adaptation to changing environmental conditions. We investigated the dynamics of expression of MTS1338, a small non-coding RNA of Mycobacterium tuberculosis, in the mouse model in vivo, regulation of its expression in the infected macrophages, and the consequences of its overexpression in bacterial cultures. Here we demonstrate that MTS1338 significantly contributes to host-pathogen interactions. Activation of the host immune system triggered NO-inducible up-regulation of MTS1338 in macrophage-engulfed mycobacteria. Constitutive overexpression of MTS1338 in cultured mycobacteria improved their survival in vitro under low pH conditions. MTS1338 up-regulation launched a spectrum of shifts in the transcriptome profile similar to those reported for M. tuberculosis adaptation to hostile intra-macrophage environment. Using the RNA-seq approach, we demonstrate that gene expression changes accompanying MTS1338 overexpression indicate reduction in translational activity and bacterial growth. These changes indicate mycobacteria entering the dormant state. Taken together, our results suggest a direct involvement of this sRNA in the interplay between mycobacteria and the host immune system during infectious process.
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Affiliation(s)
- Elena G. Salina
- Laboratory of Biochemistry of Stresses in Microorganisms, Bach Institute of Biochemistry, Research Center of Biotechnology, Moscow, Russia
| | - Artem Grigorov
- Laboratory of Regulatory Transcriptomics, Department of Genomics and Postgenomic Technologies, Shemyakin and Ovchinnikov Institute of Bioorganic Chemistry, Moscow, Russia
| | - Yulia Skvortsova
- Laboratory of Regulatory Transcriptomics, Department of Genomics and Postgenomic Technologies, Shemyakin and Ovchinnikov Institute of Bioorganic Chemistry, Moscow, Russia
| | - Konstantin Majorov
- Laboratory for Immunogenetics, Department of Immunology, Central Institute for Tuberculosis, Moscow, Russia
| | - Oksana Bychenko
- Laboratory of Regulatory Transcriptomics, Department of Genomics and Postgenomic Technologies, Shemyakin and Ovchinnikov Institute of Bioorganic Chemistry, Moscow, Russia
| | - Albina Ostrik
- Laboratory of Biochemistry of Stresses in Microorganisms, Bach Institute of Biochemistry, Research Center of Biotechnology, Moscow, Russia
| | - Nadezhda Logunova
- Laboratory for Immunogenetics, Department of Immunology, Central Institute for Tuberculosis, Moscow, Russia
| | - Dmitriy Ignatov
- Laboratory of Regulatory Transcriptomics, Department of Genomics and Postgenomic Technologies, Shemyakin and Ovchinnikov Institute of Bioorganic Chemistry, Moscow, Russia
| | - Arseny Kaprelyants
- Laboratory of Biochemistry of Stresses in Microorganisms, Bach Institute of Biochemistry, Research Center of Biotechnology, Moscow, Russia
| | - Alexander Apt
- Laboratory for Immunogenetics, Department of Immunology, Central Institute for Tuberculosis, Moscow, Russia
| | - Tatyana Azhikina
- Laboratory of Regulatory Transcriptomics, Department of Genomics and Postgenomic Technologies, Shemyakin and Ovchinnikov Institute of Bioorganic Chemistry, Moscow, Russia
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17
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Islam ZF, Cordero PRF, Greening C. Putative Iron-Sulfur Proteins Are Required for Hydrogen Consumption and Enhance Survival of Mycobacteria. Front Microbiol 2019; 10:2749. [PMID: 31824474 PMCID: PMC6883350 DOI: 10.3389/fmicb.2019.02749] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2019] [Accepted: 11/12/2019] [Indexed: 01/01/2023] Open
Abstract
Aerobic soil bacteria persist by scavenging molecular hydrogen (H2) from the atmosphere. This key process is the primary sink in the biogeochemical hydrogen cycle and supports the productivity of oligotrophic ecosystems. In Mycobacterium smegmatis, atmospheric H2 oxidation is catalyzed by two phylogenetically distinct [NiFe]-hydrogenases, Huc (group 2a) and Hhy (group 1h). However, it is currently unresolved how these enzymes transfer electrons derived from H2 oxidation into the aerobic respiratory chain. In this work, we used genetic approaches to confirm that two putative iron-sulfur cluster proteins encoded on the hydrogenase structural operons, HucE and HhyE, are required for H2 consumption in M. smegmatis. Sequence analysis show that these proteins, while homologous, fall into distinct phylogenetic clades and have distinct metal-binding motifs. H2 oxidation was reduced when the genes encoding these proteins were deleted individually and was eliminated when they were deleted in combination. In turn, the growth yield and long-term survival of these deletion strains was modestly but significantly reduced compared to the parent strain. In both biochemical and phenotypic assays, the mutant strains lacking the putative iron-sulfur proteins phenocopied those of hydrogenase structural subunit mutants. We hypothesize that these proteins mediate electron transfer between the catalytic subunits of the hydrogenases and the menaquinone pool of the M. smegmatis respiratory chain; however, other roles (e.g., in maturation) are also plausible and further work is required to resolve their role. The conserved nature of these proteins within most Hhy- or Huc-encoding organisms suggests that these proteins are important determinants of atmospheric H2 oxidation.
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Affiliation(s)
| | | | - Chris Greening
- School of Biological Sciences, Monash University, Clayton, VIC, Australia
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18
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Greening C, Geier R, Wang C, Woods LC, Morales SE, McDonald MJ, Rushton-Green R, Morgan XC, Koike S, Leahy SC, Kelly WJ, Cann I, Attwood GT, Cook GM, Mackie RI. Diverse hydrogen production and consumption pathways influence methane production in ruminants. ISME JOURNAL 2019; 13:2617-2632. [PMID: 31243332 PMCID: PMC6776011 DOI: 10.1038/s41396-019-0464-2] [Citation(s) in RCA: 96] [Impact Index Per Article: 19.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/07/2018] [Revised: 06/03/2019] [Accepted: 06/07/2019] [Indexed: 01/17/2023]
Abstract
Farmed ruminants are the largest source of anthropogenic methane emissions globally. The methanogenic archaea responsible for these emissions use molecular hydrogen (H2), produced during bacterial and eukaryotic carbohydrate fermentation, as their primary energy source. In this work, we used comparative genomic, metatranscriptomic and co-culture-based approaches to gain a system-wide understanding of the organisms and pathways responsible for ruminal H2 metabolism. Two-thirds of sequenced rumen bacterial and archaeal genomes encode enzymes that catalyse H2 production or consumption, including 26 distinct hydrogenase subgroups. Metatranscriptomic analysis confirmed that these hydrogenases are differentially expressed in sheep rumen. Electron-bifurcating [FeFe]-hydrogenases from carbohydrate-fermenting Clostridia (e.g., Ruminococcus) accounted for half of all hydrogenase transcripts. Various H2 uptake pathways were also expressed, including methanogenesis (Methanobrevibacter), fumarate and nitrite reduction (Selenomonas), and acetogenesis (Blautia). Whereas methanogenesis-related transcripts predominated in high methane yield sheep, alternative uptake pathways were significantly upregulated in low methane yield sheep. Complementing these findings, we observed significant differential expression and activity of the hydrogenases of the hydrogenogenic cellulose fermenter Ruminococcus albus and the hydrogenotrophic fumarate reducer Wolinella succinogenes in co-culture compared with pure culture. We conclude that H2 metabolism is a more complex and widespread trait among rumen microorganisms than previously recognised. There is evidence that alternative hydrogenotrophs, including acetogenic and respiratory bacteria, can prosper in the rumen and effectively compete with methanogens for H2. These findings may help to inform ongoing strategies to mitigate methane emissions by increasing flux through alternative H2 uptake pathways, including through animal selection, dietary supplementation and methanogenesis inhibitors.
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Affiliation(s)
- Chris Greening
- School of Biological Sciences, Monash University, Clayton, VIC, 3800, Australia.
| | - Renae Geier
- Department of Animal Sciences and Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
| | - Cecilia Wang
- Department of Microbiology and Immunology, University of Otago, Dunedin, 9016, New Zealand
| | - Laura C Woods
- School of Biological Sciences, Monash University, Clayton, VIC, 3800, Australia
| | - Sergio E Morales
- Department of Microbiology and Immunology, University of Otago, Dunedin, 9016, New Zealand
| | - Michael J McDonald
- School of Biological Sciences, Monash University, Clayton, VIC, 3800, Australia
| | - Rowena Rushton-Green
- Department of Microbiology and Immunology, University of Otago, Dunedin, 9016, New Zealand
| | - Xochitl C Morgan
- Department of Microbiology and Immunology, University of Otago, Dunedin, 9016, New Zealand
| | - Satoshi Koike
- Research Faculty of Agriculture, Hokkaido University, Sapporo, Japan
| | - Sinead C Leahy
- Grasslands Research Centre, AgResearch Ltd., Palmerston North, 4410, New Zealand
| | | | - Isaac Cann
- Department of Animal Sciences and Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
| | - Graeme T Attwood
- Grasslands Research Centre, AgResearch Ltd., Palmerston North, 4410, New Zealand
| | - Gregory M Cook
- Department of Microbiology and Immunology, University of Otago, Dunedin, 9016, New Zealand
| | - Roderick I Mackie
- Department of Animal Sciences and Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA.
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19
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Abstract
The availability of renewable energy technologies is increasing dramatically across the globe thanks to their growing maturity. However, large scale electrical energy storage and retrieval will almost certainly be a required in order to raise the penetration of renewable sources into the grid. No present energy storage technology has the perfect combination of high power and energy density, low financial and environmental cost, lack of site restrictions, long cycle and calendar lifespan, easy materials availability, and fast response time. Engineered electroactive microbes could address many of the limitations of current energy storage technologies by enabling rewired carbon fixation, a process that spatially separates reactions that are normally carried out together in a photosynthetic cell and replaces the least efficient with non-biological equivalents. If successful, this could allow storage of renewable electricity through electrochemical or enzymatic fixation of carbon dioxide and subsequent storage as carbon-based energy storage molecules including hydrocarbons and non-volatile polymers at high efficiency. In this article we compile performance data on biological and non-biological component choices for rewired carbon fixation systems and identify pressing research and engineering challenges.
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20
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Baffert C, Kpebe A, Avilan L, Brugna M. Hydrogenases and H 2 metabolism in sulfate-reducing bacteria of the Desulfovibrio genus. Adv Microb Physiol 2019; 74:143-189. [PMID: 31126530 DOI: 10.1016/bs.ampbs.2019.03.001] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Hydrogen metabolism plays a central role in sulfate-reducing bacteria of the Desulfovibrio genus and is based on hydrogenases that catalyze the reversible conversion of protons into dihydrogen. These metabolically versatile microorganisms possess a complex hydrogenase system composed of several enzymes of both [FeFe]- and [NiFe]-type that can vary considerably from one Desulfovibrio species to another. This review covers the molecular and physiological aspects of hydrogenases and H2 metabolism in Desulfovibrio but focuses particularly on our model bacterium Desulfovibrio fructosovorans. The search of hydrogenase genes in more than 30 sequenced genomes provides an overview of the distribution of these enzymes in Desulfovibrio. Our discussion will consider the significance of the involvement of electron-bifurcation in H2 metabolism.
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Affiliation(s)
- Carole Baffert
- Aix-Marseille University, CNRS, BIP, 31 Chemin Joseph Aiguier, 13402 Marseille, France
| | - Arlette Kpebe
- Aix-Marseille University, CNRS, BIP, 31 Chemin Joseph Aiguier, 13402 Marseille, France
| | - Luisana Avilan
- Aix-Marseille University, CNRS, BIP, 31 Chemin Joseph Aiguier, 13402 Marseille, France
| | - Myriam Brugna
- Aix-Marseille University, CNRS, BIP, 31 Chemin Joseph Aiguier, 13402 Marseille, France
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21
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Kessler AJ, Chen YJ, Waite DW, Hutchinson T, Koh S, Popa ME, Beardall J, Hugenholtz P, Cook PLM, Greening C. Bacterial fermentation and respiration processes are uncoupled in anoxic permeable sediments. Nat Microbiol 2019; 4:1014-1023. [DOI: 10.1038/s41564-019-0391-z] [Citation(s) in RCA: 46] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2018] [Accepted: 01/28/2019] [Indexed: 11/09/2022]
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22
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23
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Bay S, Ferrari B, Greening C. Life without water: how do bacteria generate biomass in desert ecosystems? MICROBIOLOGY AUSTRALIA 2018. [DOI: 10.1071/ma18008] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Many of the world's most arid deserts harbour surprisingly diverse communities of heterotrophic bacteria. These organisms persist in surface soils under extreme climatic conditions, despite lacking obvious energy inputs from phototrophic primary producers. A longstanding conundrum has been how these communities sustain enough energy to maintain their diversity and biomass. We recently helped to resolve this conundrum by demonstrating that some desert communities are structured by a minimalistic mode of chemosynthetic primary production, where atmospheric trace gases, not sunlight, serve as the main energy sources. These findings are supported by pure culture studies that suggest atmospheric trace gases are dependable energy sources for the long-term survival of dormant soil bacteria. We predict that atmospheric trace gases may be a major energy source for desert ecosystems worldwide.
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Kruse S, Goris T, Wolf M, Wei X, Diekert G. The NiFe Hydrogenases of the Tetrachloroethene-Respiring Epsilonproteobacterium Sulfurospirillum multivorans: Biochemical Studies and Transcription Analysis. Front Microbiol 2017; 8:444. [PMID: 28373866 PMCID: PMC5357620 DOI: 10.3389/fmicb.2017.00444] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2017] [Accepted: 03/03/2017] [Indexed: 12/24/2022] Open
Abstract
The organohalide-respiring Epsilonproteobacterium Sulfurospirillum multivorans is able to grow with hydrogen as electron donor and with tetrachloroethene (PCE) as electron acceptor; PCE is reductively dechlorinated to cis-1,2-dichloroethene. Recently, a genomic survey revealed the presence of four gene clusters encoding NiFe hydrogenases in its genome, one of which is presumably periplasmic and membrane-bound (MBH), whereas the remaining three are cytoplasmic. To explore the role and regulation of the four hydrogenases, quantitative real-time PCR and biochemical studies were performed with S. multivorans cells grown under different growth conditions. The large subunit genes of the MBH and of a cytoplasmic group 4 hydrogenase, which is assumed to be membrane-associated, show high transcript levels under nearly all growth conditions tested, pointing toward a constitutive expression in S. multivorans. The gene transcripts encoding the large subunits of the other two hydrogenases were either not detected at all or only present at very low amounts. The presence of MBH under all growth conditions tested, even with oxygen as electron acceptor under microoxic conditions, indicates that MBH gene transcription is not regulated in contrast to other facultative hydrogen-oxidizing bacteria. The MBH showed quinone-reactivity and a characteristic UV/VIS spectrum implying a cytochrome b as membrane-integral subunit. Cell extracts of S. multivorans were subjected to native polyacrylamide gel electrophoresis (PAGE) and hydrogen oxidizing activity was tested by native staining. Only one band was detected at about 270 kDa in the particulate fraction of the extracts, indicating that there is only one hydrogen-oxidizing enzyme present in S. multivorans. An enrichment of this enzyme and SDS PAGE revealed a subunit composition corresponding to that of the MBH. From these findings we conclude that the MBH is the electron-donating enzyme system in the PCE respiratory chain. The roles for the other three hydrogenases remain unproven. The group 4 hydrogenase might be involved in hydrogen production upon fermentative growth.
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Affiliation(s)
- Stefan Kruse
- Department of Applied and Ecological Microbiology, Institute of Microbiology Friedrich Schiller University, Germany
| | - Tobias Goris
- Department of Applied and Ecological Microbiology, Institute of Microbiology Friedrich Schiller University, Germany
| | - Maria Wolf
- Department of Applied and Ecological Microbiology, Institute of Microbiology Friedrich Schiller University, Germany; Dianovis GmbHGreiz, Germany
| | - Xi Wei
- Department of Applied and Ecological Microbiology, Institute of Microbiology Friedrich Schiller University, Germany; Department Isotope Biogeochemistry, Helmholtz Centre for Environmental Research-UFZLeipzig, Germany; YMC Europe GmbHDinslaken, Germany
| | - Gabriele Diekert
- Department of Applied and Ecological Microbiology, Institute of Microbiology Friedrich Schiller University, Germany
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Søndergaard D, Pedersen CNS, Greening C. HydDB: A web tool for hydrogenase classification and analysis. Sci Rep 2016; 6:34212. [PMID: 27670643 PMCID: PMC5037454 DOI: 10.1038/srep34212] [Citation(s) in RCA: 286] [Impact Index Per Article: 35.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2016] [Accepted: 09/09/2016] [Indexed: 01/22/2023] Open
Abstract
H2 metabolism is proposed to be the most ancient and diverse mechanism of energy-conservation. The metalloenzymes mediating this metabolism, hydrogenases, are encoded by over 60 microbial phyla and are present in all major ecosystems. We developed a classification system and web tool, HydDB, for the structural and functional analysis of these enzymes. We show that hydrogenase function can be predicted by primary sequence alone using an expanded classification scheme (comprising 29 [NiFe], 8 [FeFe], and 1 [Fe] hydrogenase classes) that defines 11 new classes with distinct biological functions. Using this scheme, we built a web tool that rapidly and reliably classifies hydrogenase primary sequences using a combination of k-nearest neighbors' algorithms and CDD referencing. Demonstrating its capacity, the tool reliably predicted hydrogenase content and function in 12 newly-sequenced bacteria, archaea, and eukaryotes. HydDB provides the capacity to browse the amino acid sequences of 3248 annotated hydrogenase catalytic subunits and also contains a detailed repository of physiological, biochemical, and structural information about the 38 hydrogenase classes defined here. The database and classifier are freely and publicly available at http://services.birc.au.dk/hyddb/.
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Affiliation(s)
- Dan Søndergaard
- Aarhus University, Bioinformatics Research Centre, C.F. Møllers Allé 8, Aarhus DK-8000, Denmark
| | | | - Chris Greening
- The Commonwealth Scientific and Industrial Research Organisation, Land and Water Flagship, Clunies Ross Street, Acton, ACT 2601, Australia
- Monash University, School of Biological Sciences, Clayton, VIC 3800, Australia
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Boboescu IZ, Gherman VD, Lakatos G, Pap B, Bíró T, Maróti G. Surpassing the current limitations of biohydrogen production systems: The case for a novel hybrid approach. BIORESOURCE TECHNOLOGY 2016; 204:192-201. [PMID: 26790867 DOI: 10.1016/j.biortech.2015.12.083] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/06/2015] [Revised: 12/22/2015] [Accepted: 12/28/2015] [Indexed: 06/05/2023]
Abstract
The steadily increase of global energy requirements has brought about a general agreement on the need for novel renewable and environmentally friendly energy sources and carriers. Among the alternatives to a fossil fuel-based economy, hydrogen gas is considered a game-changer. Certain methods of hydrogen production can utilize various low-priced industrial and agricultural wastes as substrate, thus coupling organic waste treatment with renewable energy generation. Among these approaches, different biological strategies have been investigated and successfully implemented in laboratory-scale systems. Although promising, several key aspects need further investigation in order to push these technologies towards large-scale industrial implementation. Some of the major scientific and technical bottlenecks will be discussed, along with possible solutions, including a thorough exploration of novel research combining microbial dark fermentation and algal photoheterotrophic degradation systems, integrated with wastewater treatment and metabolic by-products usage.
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Affiliation(s)
- Iulian Zoltan Boboescu
- Polytechnic University of Timisoara, Victoriei Square, nr. 2, 300006 Timisoara, Romania; Hungarian Academy of Sciences, Biological Research Centre Szeged, Temesvari krt. 62, 6726 Szeged, Hungary
| | - Vasile Daniel Gherman
- Polytechnic University of Timisoara, Victoriei Square, nr. 2, 300006 Timisoara, Romania
| | - Gergely Lakatos
- Hungarian Academy of Sciences, Biological Research Centre Szeged, Temesvari krt. 62, 6726 Szeged, Hungary
| | - Bernadett Pap
- Seqomics Biotechnology Ltd., Vállalkozók útja 7, 6782 Mórahalom, Hungary
| | - Tibor Bíró
- Szent István University, Faculty of Economics, Agricultural and Health Studies, Szarvas, Hungary
| | - Gergely Maróti
- Polytechnic University of Timisoara, Victoriei Square, nr. 2, 300006 Timisoara, Romania; Hungarian Academy of Sciences, Biological Research Centre Szeged, Temesvari krt. 62, 6726 Szeged, Hungary.
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Abstract
We have known for 40 years that soils can consume the trace amounts of molecular hydrogen (H2) found in the Earth’s atmosphere.This process is predicted to be the most significant term in the global hydrogen cycle. However, the organisms and enzymes responsible for this process were only recently identified. Pure culture experiments demonstrated that several species of Actinobacteria, including streptomycetes and mycobacteria, can couple the oxidation of atmospheric H2 to the reduction of ambient O2. A combination of genetic, biochemical, and phenotypic studies suggest that these organisms primarily use this fuel source to sustain electron input into the respiratory chain during energy starvation. This process is mediated by a specialized enzyme, the group 5 [NiFe]-hydrogenase, which is unusual for its high affinity, oxygen insensitivity, and thermostability. Atmospheric hydrogen scavenging is a particularly dependable mode of energy generation, given both the ubiquity of the substrate and the stress tolerance of its catalyst. This minireview summarizes the recent progress in understanding how and why certain organisms scavenge atmospheric H2. In addition, it provides insight into the wider significance of hydrogen scavenging in global H2 cycling and soil microbial ecology.
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Liot Q, Constant P. Breathing air to save energy--new insights into the ecophysiological role of high-affinity [NiFe]-hydrogenase in Streptomyces avermitilis. Microbiologyopen 2015; 5:47-59. [PMID: 26541261 PMCID: PMC4767420 DOI: 10.1002/mbo3.310] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2015] [Revised: 08/25/2015] [Accepted: 10/06/2015] [Indexed: 11/23/2022] Open
Abstract
The Streptomyces avermitilis genome encodes a putative high‐affinity [NiFe]‐hydrogenase conferring the ability to oxidize tropospheric H2 in mature spores. Here, we used a combination of transcriptomic and mutagenesis approaches to shed light on the potential ecophysiological role of the enzyme. First, S. avermitilis was either exposed to low or hydrogenase‐saturating levels of H2 to investigate the impact of H2 on spore transcriptome. In total, 1293 genes were differentially expressed, with 1127 and 166 showing lower and higher expression under elevated H2 concentration, respectively. High H2 exposure lowered the expression of the Sec protein secretion pathway and ATP‐binding cassette‐transporters, with increased expression of genes encoding proteins directing carbon metabolism toward sugar anabolism and lower expression of NADH dehydrogenase in the respiratory chain. Overall, the expression of relA responsible for the synthesis of the pleiotropic alarmone ppGpp decreased upon elevated H2 exposure, which likely explained the reduced expression of antibiotic synthesis and stress response genes. Finally, deletion of hhySL genes resulted in a loss of H2 uptake activity and a dramatic loss of viability in spores. We propose that H2 is restricted to support the seed bank of Streptomyces under a unique survival–mixotrophic energy mode and discuss important ecological implications of this finding.
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Genomic and metagenomic surveys of hydrogenase distribution indicate H2 is a widely utilised energy source for microbial growth and survival. ISME JOURNAL 2015; 10:761-77. [PMID: 26405831 DOI: 10.1038/ismej.2015.153] [Citation(s) in RCA: 338] [Impact Index Per Article: 37.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/03/2015] [Revised: 06/20/2015] [Accepted: 07/20/2015] [Indexed: 11/08/2022]
Abstract
Recent physiological and ecological studies have challenged the long-held belief that microbial metabolism of molecular hydrogen (H2) is a niche process. To gain a broader insight into the importance of microbial H2 metabolism, we comprehensively surveyed the genomic and metagenomic distribution of hydrogenases, the reversible enzymes that catalyse the oxidation and evolution of H2. The protein sequences of 3286 non-redundant putative hydrogenases were curated from publicly available databases. These metalloenzymes were classified into multiple groups based on (1) amino acid sequence phylogeny, (2) metal-binding motifs, (3) predicted genetic organisation and (4) reported biochemical characteristics. Four groups (22 subgroups) of [NiFe]-hydrogenase, three groups (6 subtypes) of [FeFe]-hydrogenases and a small group of [Fe]-hydrogenases were identified. We predict that this hydrogenase diversity supports H2-based respiration, fermentation and carbon fixation processes in both oxic and anoxic environments, in addition to various H2-sensing, electron-bifurcation and energy-conversion mechanisms. Hydrogenase-encoding genes were identified in 51 bacterial and archaeal phyla, suggesting strong pressure for both vertical and lateral acquisition. Furthermore, hydrogenase genes could be recovered from diverse terrestrial, aquatic and host-associated metagenomes in varying proportions, indicating a broad ecological distribution and utilisation. Oxygen content (pO2) appears to be a central factor driving the phylum- and ecosystem-level distribution of these genes. In addition to compounding evidence that H2 was the first electron donor for life, our analysis suggests that the great diversification of hydrogenases has enabled H2 metabolism to sustain the growth or survival of microorganisms in a wide range of ecosystems to the present day. This work also provides a comprehensive expanded system for classifying hydrogenases and identifies new prospects for investigating H2 metabolism.
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Persistence of the dominant soil phylum Acidobacteria by trace gas scavenging. Proc Natl Acad Sci U S A 2015; 112:10497-502. [PMID: 26240343 DOI: 10.1073/pnas.1508385112] [Citation(s) in RCA: 72] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The majority of microbial cells in global soils exist in a spectrum of dormant states. However, the metabolic processes that enable them to survive environmental challenges, such as nutrient-limitation, remain to be elucidated. In this work, we demonstrate that energy-starved cultures of Pyrinomonas methylaliphatogenes, an aerobic heterotrophic acidobacterium isolated from New Zealand volcanic soils, persist by scavenging the picomolar concentrations of H2 distributed throughout the atmosphere. Following the transition from exponential to stationary phase due to glucose limitation, the bacterium up-regulates by fourfold the expression of an eight-gene operon encoding an actinobacteria-type H2-uptake [NiFe]-hydrogenase. Whole-cells of the organism consume atmospheric H2 in a first-order kinetic process. Hydrogen oxidation occurred most rapidly under oxic conditions and was weakly associated with the cell membrane. We propose that atmospheric H2 scavenging serves as a mechanism to sustain the respiratory chain of P. methylaliphatogenes when organic electron donors are scarce. As the first observation of H2 oxidation to our knowledge in the Acidobacteria, the second most dominant soil phylum, this work identifies new sinks in the biogeochemical H2 cycle and suggests that trace gas oxidation may be a general mechanism for microbial persistence.
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Identification, cloning and heterologous expression of active [NiFe]-hydrogenase 2 from Citrobacter sp. SG in Escherichia coli. J Biotechnol 2015; 199:1-8. [DOI: 10.1016/j.jbiotec.2015.01.025] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2014] [Revised: 01/27/2015] [Accepted: 01/29/2015] [Indexed: 11/22/2022]
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Abstract
The emergence and spread of drug-resistant pathogens and our inability to develop new antimicrobials to overcome resistance has inspired scientists to consider new targets for drug development. Cellular bioenergetics is an area showing promise for the development of new antimicrobials, particularly in the discovery of new anti-tuberculosis drugs where several new compounds have entered clinical trials. In this review, we have examined the bioenergetics of various bacterial pathogens, highlighting the versatility of electron donor and acceptor utilisation and the modularity of electron transport chain components in bacteria. In addition to re-examining classical concepts, we explore new literature that reveals the intricacies of pathogen energetics, for example, how Salmonella enterica and Campylobacter jejuni exploit host and microbiota to derive powerful electron donors and sinks; the strategies Mycobacterium tuberculosis and Pseudomonas aeruginosa use to persist in lung tissues; and the importance of sodium energetics and electron bifurcation in the chemiosmotic anaerobe Fusobacterium nucleatum. A combination of physiological, biochemical, and pharmacological data suggests that, in addition to the clinically-approved target F1Fo-ATP synthase, NADH dehydrogenase type II, succinate dehydrogenase, hydrogenase, cytochrome bd oxidase, and menaquinone biosynthesis pathways are particularly promising next-generation drug targets. The realisation of cellular energetics as a rich target space for the development of new antimicrobials will be dependent upon gaining increased understanding of the energetic processes utilised by pathogens in host environments and the ability to design bacterial-specific inhibitors of these processes.
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Hydrogen formation and its regulation in Ruminococcus albus: involvement of an electron-bifurcating [FeFe]-hydrogenase, of a non-electron-bifurcating [FeFe]-hydrogenase, and of a putative hydrogen-sensing [FeFe]-hydrogenase. J Bacteriol 2014; 196:3840-52. [PMID: 25157086 DOI: 10.1128/jb.02070-14] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Ruminococcus albus 7 has played a key role in the development of the concept of interspecies hydrogen transfer. The rumen bacterium ferments glucose to 1.3 acetate, 0.7 ethanol, 2 CO2, and 2.6 H2 when growing in batch culture and to 2 acetate, 2 CO2, and 4 H2 when growing in continuous culture in syntrophic association with H2-consuming microorganisms that keep the H2 partial pressure low. The organism uses NAD(+) and ferredoxin for glucose oxidation to acetyl coenzyme A (acetyl-CoA) and CO2, NADH for the reduction of acetyl-CoA to ethanol, and NADH and reduced ferredoxin for the reduction of protons to H2. Of all the enzymes involved, only the enzyme catalyzing the formation of H2 from NADH remained unknown. Here, we report that R. albus 7 grown in batch culture on glucose contained, besides a ferredoxin-dependent [FeFe]-hydrogenase (HydA2), a ferredoxin- and NAD-dependent electron-bifurcating [FeFe]-hydrogenase (HydABC) that couples the endergonic formation of H2 from NADH to the exergonic formation of H2 from reduced ferredoxin. Interestingly, hydA2 is adjacent to the hydS gene, which is predicted to encode an [FeFe]-hydrogenase with a C-terminal PAS domain. We showed that hydS and hydA2 are part of a larger transcriptional unit also harboring putative genes for a bifunctional acetaldehyde/ethanol dehydrogenase (Aad), serine/threonine protein kinase, serine/threonine protein phosphatase, and a redox-sensing transcriptional repressor. Since HydA2 and Aad are required only when R. albus grows at high H2 partial pressures, HydS could be a H2-sensing [FeFe]-hydrogenase involved in the regulation of their biosynthesis.
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