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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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2
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Grégoire DS, George NA, Hug LA. Microbial methane cycling in a landfill on a decadal time scale. Nat Commun 2023; 14:7402. [PMID: 37973978 PMCID: PMC10654671 DOI: 10.1038/s41467-023-43129-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2023] [Accepted: 11/01/2023] [Indexed: 11/19/2023] Open
Abstract
Landfills generate outsized environmental footprints due to microbial degradation of organic matter in municipal solid waste, which produces the potent greenhouse gas methane. With global solid waste production predicted to increase substantially in the next few decades, there is a pressing need to better understand the temporal dynamics of biogeochemical processes that control methane cycling in landfills. Here, we use metagenomic approaches to characterize microbial methane cycling in waste that was landfilled over 39 years. Our analyses indicate that newer waste supports more diverse communities with similar composition compared to older waste, which contains lower diversity and more varied communities. Older waste contains primarily autotrophic organisms with versatile redox metabolisms, whereas newer waste is dominated by anaerobic fermenters. Methane-producing microbes are more abundant, diverse, and metabolically versatile in new waste compared to old waste. Our findings indicate that predictive models for methane emission in landfills overlook methane oxidation in the absence of oxygen, as well as certain microbial lineages that can potentially contribute to methane sinks in diverse habitats.
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Affiliation(s)
- Daniel S Grégoire
- Department of Biology, University of Waterloo, Waterloo, ON, N2L 3G1, Canada.
- Department of Chemistry, Carleton University, Ottawa, ON, K1S 5B6, Canada.
| | - Nikhil A George
- Department of Biology, University of Waterloo, Waterloo, ON, N2L 3G1, Canada
| | - Laura A Hug
- Department of Biology, University of Waterloo, Waterloo, ON, N2L 3G1, Canada.
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3
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Awala SI, Gwak JH, Kim Y, Seo C, Strazzulli A, Kim SG, Rhee SK. Methylacidiphilum caldifontis gen. nov., sp. nov., a thermoacidophilic methane-oxidizing bacterium from an acidic geothermal environment, and descriptions of the family Methylacidiphilaceae fam. nov. and order Methylacidiphilales ord. nov. Int J Syst Evol Microbiol 2023; 73. [PMID: 37791995 DOI: 10.1099/ijsem.0.006085] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/05/2023] Open
Abstract
Strain IT6T, a thermoacidophilic and facultative methane-oxidizing bacterium, was isolated from a mud-water mixture collected from Pisciarelli hot spring in Pozzuoli, Italy. The novel strain is white when grown in liquid or solid media and forms Gram-negative rod-shaped, non-flagellated, non-motile cells. It conserves energy by aerobically oxidizing methane and hydrogen while deriving carbon from carbon dioxide fixation. Strain IT6T had three complete pmoCAB operons encoding particulate methane monooxygenase and genes encoding group 1d and 3b [NiFe] hydrogenases. Simple carbon-carbon substrates such as ethanol, 2-propanol, acetone, acetol and propane-1,2-diol were used as alternative electron donors and carbon sources. Optimal growth occurred at 50-55°C and between pH 2.0-3.0. The major fatty acids were C18 : 0, C15 : 0 anteiso, C14 : 0 iso, C16 : 0 and C14 : 0, and the main polar lipids were phosphatidylethanolamine, aminophospholipid, phosphatidylglycerol, diphosphatidylglycerol, some unidentified phospholipids and glycolipids, and other unknown polar lipids. Strain IT6T has a genome size of 2.19 Mbp and a G+C content of 40.70 mol%. Relative evolutionary divergence using 120 conserved single-copy marker genes (bac120) and phylogenetic analyses based on bac120 and 16S rRNA gene sequences showed that strain IT6T is affiliated with members of the proposed order 'Methylacidiphilales' of the class Verrucomicrobiia in the phylum Verrucomicrobiota. It shared a 16S rRNA gene sequence identity of >96 % with cultivated isolates in the genus 'Methylacidiphilum' of the family 'Methylacidiphilaceae', which are thermoacidophilic methane-oxidizing bacteria. 'Methylacidiphilum sp.' Phi (100 %), 'Methylacidiphilum infernorum' V4 (99.02 %) and 'Methylacidiphilum sp.' RTK17.1 (99.02 %) were its closest relatives. Its physiological and genomic properties were consistent with those of other isolated 'Methylacidiphilum' species. Based on these results, we propose the name Methylacidiphilum caldifontis gen. nov., sp. nov. to accommodate strain IT6T (=KCTC 92103T=JCM 39288T). We also formally propose that the names Methylacidiphilaceae fam. nov. and Methylacidiphilales ord. nov. to accommodate the genus Methylacidiphilum gen. nov.
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Affiliation(s)
- Samuel Imisi Awala
- Department of Biological Sciences and Biotechnology, Chungbuk National University, 1 Chungdae-ro, Seowon-Gu, Cheongju 28644, Republic of Korea
| | - Joo-Han Gwak
- Department of Biological Sciences and Biotechnology, Chungbuk National University, 1 Chungdae-ro, Seowon-Gu, Cheongju 28644, Republic of Korea
| | - Yongman Kim
- Department of Biological Sciences and Biotechnology, Chungbuk National University, 1 Chungdae-ro, Seowon-Gu, Cheongju 28644, Republic of Korea
| | - Chanmee Seo
- Department of Biological Sciences and Biotechnology, Chungbuk National University, 1 Chungdae-ro, Seowon-Gu, Cheongju 28644, Republic of Korea
| | - Andrea Strazzulli
- Department of Biology, University of Naples "Federico II", Complesso Universitario Di Monte S. Angelo, Via Cupa Nuova Cinthia 21, 80126, Naples, Italy
| | - Song-Gun Kim
- University of Science and Technology, Yuseong-gu, Daejeon 305-850, Republic of Korea
- Biological Resource Center/ Korean Collection for Type Culture (KCTC), Korea Research Institute of Bioscience and Biotechnology, 181 Ipsingil, Jeongeup-si, Jeollabuk-do, 56212, Republic of Korea
| | - Sung-Keun Rhee
- Department of Biological Sciences and Biotechnology, Chungbuk National University, 1 Chungdae-ro, Seowon-Gu, Cheongju 28644, Republic of Korea
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4
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Schmitz RA, Peeters SH, Mohammadi SS, Berben T, van Erven T, Iosif CA, van Alen T, Versantvoort W, Jetten MSM, Op den Camp HJM, Pol A. Simultaneous sulfide and methane oxidation by an extremophile. Nat Commun 2023; 14:2974. [PMID: 37221165 DOI: 10.1038/s41467-023-38699-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2023] [Accepted: 05/11/2023] [Indexed: 05/25/2023] Open
Abstract
Hydrogen sulfide (H2S) and methane (CH4) are produced in anoxic environments through sulfate reduction and organic matter decomposition. Both gases diffuse upwards into oxic zones where aerobic methanotrophs mitigate CH4 emissions by oxidizing this potent greenhouse gas. Although methanotrophs in myriad environments encounter toxic H2S, it is virtually unknown how they are affected. Here, through extensive chemostat culturing we show that a single microorganism can oxidize CH4 and H2S simultaneously at equally high rates. By oxidizing H2S to elemental sulfur, the thermoacidophilic methanotroph Methylacidiphilum fumariolicum SolV alleviates the inhibitory effects of H2S on methanotrophy. Strain SolV adapts to increasing H2S by expressing a sulfide-insensitive ba3-type terminal oxidase and grows as chemolithoautotroph using H2S as sole energy source. Genomic surveys revealed putative sulfide-oxidizing enzymes in numerous methanotrophs, suggesting that H2S oxidation is much more widespread in methanotrophs than previously assumed, enabling them to connect carbon and sulfur cycles in novel ways.
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Affiliation(s)
- Rob A Schmitz
- Department of Microbiology, Radboud Institute for Biological and Environmental Sciences, Radboud University, Heyendaalseweg 135, 6525AJ, Nijmegen, The Netherlands
- Institute of Biogeochemistry and Pollutant Dynamics, Department of Environmental Systems Science, ETH Zurich, 8092, Zurich, Switzerland
| | - Stijn H Peeters
- Department of Microbiology, Radboud Institute for Biological and Environmental Sciences, Radboud University, Heyendaalseweg 135, 6525AJ, Nijmegen, The Netherlands
| | - Sepehr S Mohammadi
- Department of Microbiology, Radboud Institute for Biological and Environmental Sciences, Radboud University, Heyendaalseweg 135, 6525AJ, Nijmegen, The Netherlands
| | - Tom Berben
- Department of Microbiology, Radboud Institute for Biological and Environmental Sciences, Radboud University, Heyendaalseweg 135, 6525AJ, Nijmegen, The Netherlands
| | - Timo van Erven
- Department of Microbiology, Radboud Institute for Biological and Environmental Sciences, Radboud University, Heyendaalseweg 135, 6525AJ, Nijmegen, The Netherlands
| | - Carmen A Iosif
- Department of Microbiology, Radboud Institute for Biological and Environmental Sciences, Radboud University, Heyendaalseweg 135, 6525AJ, Nijmegen, The Netherlands
| | - Theo van Alen
- Department of Microbiology, Radboud Institute for Biological and Environmental Sciences, Radboud University, Heyendaalseweg 135, 6525AJ, Nijmegen, The Netherlands
| | - Wouter Versantvoort
- Department of Microbiology, Radboud Institute for Biological and Environmental Sciences, Radboud University, Heyendaalseweg 135, 6525AJ, Nijmegen, The Netherlands
| | - Mike S M Jetten
- Department of Microbiology, Radboud Institute for Biological and Environmental Sciences, Radboud University, Heyendaalseweg 135, 6525AJ, Nijmegen, The Netherlands
| | - Huub J M Op den Camp
- Department of Microbiology, Radboud Institute for Biological and Environmental Sciences, Radboud University, Heyendaalseweg 135, 6525AJ, Nijmegen, The Netherlands.
| | - Arjan Pol
- Department of Microbiology, Radboud Institute for Biological and Environmental Sciences, Radboud University, Heyendaalseweg 135, 6525AJ, Nijmegen, The Netherlands
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5
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Hwangbo M, Shao Y, Hatzinger PB, Chu KH. Acidophilic methanotrophs: Occurrence, diversity, and possible bioremediation applications. ENVIRONMENTAL MICROBIOLOGY REPORTS 2023. [PMID: 37041665 DOI: 10.1111/1758-2229.13156] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2023] [Accepted: 03/23/2023] [Indexed: 06/19/2023]
Abstract
Methanotrophs have been identified and isolated from acidic environments such as wetlands, acidic soils, peat bogs, and groundwater aquifers. Due to their methane (CH4 ) utilization as a carbon and energy source, acidophilic methanotrophs are important in controlling the release of atmospheric CH4 , an important greenhouse gas, from acidic wetlands and other environments. Methanotrophs have also played an important role in the biodegradation and bioremediation of a variety of pollutants including chlorinated volatile organic compounds (CVOCs) using CH4 monooxygenases via a process known as cometabolism. Under neutral pH conditions, anaerobic bioremediation via carbon source addition is a commonly used and highly effective approach to treat CVOCs in groundwater. However, complete dechlorination of CVOCs is typically inhibited at low pH. Acidophilic methanotrophs have recently been observed to degrade a range of CVOCs at pH < 5.5, suggesting that cometabolic treatment may be an option for CVOCs and other contaminants in acidic aquifers. This paper provides an overview of the occurrence, diversity, and physiological activities of methanotrophs in acidic environments and highlights the potential application of these organisms for enhancing contaminant biodegradation and bioremediation.
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Affiliation(s)
- Myung Hwangbo
- Zachry Department of Civil and Environmental Engineering, Texas A&M University, College Station, Texas, USA
| | - Yiru Shao
- Zachry Department of Civil and Environmental Engineering, Texas A&M University, College Station, Texas, USA
| | - Paul B Hatzinger
- Aptim Federal Services, LLC, 17 Princess Road, Lawrenceville, New Jersey, USA
| | - Kung-Hui Chu
- Zachry Department of Civil and Environmental Engineering, Texas A&M University, College Station, Texas, USA
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6
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Neira G, Vergara E, Holmes DS. Genome-guided prediction of acid resistance mechanisms in acidophilic methanotrophs of phylogenetically deep-rooted Verrucomicrobia isolated from geothermal environments. Front Microbiol 2022; 13:900531. [PMID: 36212841 PMCID: PMC9543262 DOI: 10.3389/fmicb.2022.900531] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2022] [Accepted: 07/22/2022] [Indexed: 11/13/2022] Open
Abstract
Verrucomicrobia are a group of microorganisms that have been proposed to be deeply rooted in the Tree of Life. Some are methanotrophs that oxidize the potent greenhouse gas methane and are thus important in decreasing atmospheric concentrations of the gas, potentially ameliorating climate change. They are widespread in various environments including soil and fresh or marine waters. Recently, a clade of extremely acidophilic Verrucomicrobia, flourishing at pH < 3, were described from high-temperature geothermal ecosystems. This novel group could be of interest for studies about the emergence of life on Earth and to astrobiologists as homologs for possible extraterrestrial life. In this paper, we describe predicted mechanisms for survival of this clade at low pH and suggest its possible evolutionary trajectory from an inferred neutrophilic ancestor. Extreme acidophiles are defined as organisms that thrive in extremely low pH environments (≤ pH 3). Many are polyextremophiles facing high temperatures and high salt as well as low pH. They are important to study for both providing fundamental insights into biological mechanisms of survival and evolution in such extreme environments and for understanding their roles in biotechnological applications such as industrial mineral recovery (bioleaching) and mitigation of acid mine drainage. They are also, potentially, a rich source of novel genes and pathways for the genetic engineering of microbial strains. Acidophiles of the Verrucomicrobia phylum are unique as they are the only known aerobic methanotrophs that can grow optimally under acidic (pH 2–3) and moderately thermophilic conditions (50–60°C). Three moderately thermophilic genera, namely Methylacidiphilum, Methylacidimicrobium, and Ca. Methylacidithermus, have been described in geothermal environments. Most of the investigations of these organisms have focused on their methane oxidizing capabilities (methanotrophy) and use of lanthanides as a protein cofactor, with no extensive study that sheds light on the mechanisms that they use to flourish at extremely low pH. In this paper, we extend the phylogenetic description of this group of acidophiles using whole genome information and we identify several mechanisms, potentially involved in acid resistance, including “first line of defense” mechanisms that impede the entry of protons into the cell. These include the presence of membrane-associated hopanoids, multiple copies of the outer membrane protein (Slp), and inner membrane potassium channels (kup, kdp) that generate a reversed membrane potential repelling the intrusion of protons. Acidophilic Verrucomicrobia also display a wide array of proteins potentially involved in the “second line of defense” where protons that evaded the first line of defense and entered the cell are expelled or neutralized, such as the glutamate decarboxylation (gadAB) and phosphate-uptake systems. An exclusive N-type ATPase F0-F1 was identified only in acidophiles of Verrucomicrobia and is predicted to be a specific adaptation in these organisms. Phylogenetic analyses suggest that many predicted mechanisms are evolutionarily conserved and most likely entered the acidophilic lineage of Verrucomicrobia by vertical descent from a common ancestor. However, it is likely that some defense mechanisms such as gadA and kup entered the acidophilic Verrucomicrobia lineage by horizontal gene transfer.
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Affiliation(s)
- Gonzalo Neira
- Center for Bioinformatics and Genome Biology, Centro Ciencia & Vida, Fundación Ciencia & Vida, Santiago, Chile
| | - Eva Vergara
- Center for Bioinformatics and Genome Biology, Centro Ciencia & Vida, Fundación Ciencia & Vida, Santiago, Chile
- Facultad de Medicina y Ciencia, Universidad San Sebastián, Santiago, Chile
| | - David S. Holmes
- Center for Bioinformatics and Genome Biology, Centro Ciencia & Vida, Fundación Ciencia & Vida, Santiago, Chile
- Facultad de Medicina y Ciencia, Universidad San Sebastián, Santiago, Chile
- *Correspondence: David S. Holmes
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7
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Abstract
Wetlands are the major natural source of methane, an important greenhouse gas. The sulfur and methane cycles in wetlands are linked—e.g., a strong sulfur cycle can inhibit methanogenesis. Although there has historically been a clear distinction drawn between methane and sulfur oxidizers, here, we isolated a methanotroph that also performed respiratory oxidization of sulfur compounds. We experimentally demonstrated that thiotrophy and methanotrophy are metabolically compatible, and both metabolisms could be expressed simultaneously in a single microorganism. These findings suggest that mixotrophic methane/sulfur-oxidizing bacteria are a previously overlooked component of environmental methane and sulfur cycles. This creates a framework for a better understanding of these redox cycles in natural and engineered wetlands. Natural and anthropogenic wetlands are major sources of the atmospheric greenhouse gas methane. Methane emissions from wetlands are mitigated by methanotrophic bacteria at the oxic–anoxic interface, a zone of intense redox cycling of carbon, sulfur, and nitrogen compounds. Here, we report on the isolation of an aerobic methanotrophic bacterium, ‘Methylovirgula thiovorans' strain HY1, which possesses metabolic capabilities never before found in any methanotroph. Most notably, strain HY1 is the first bacterium shown to aerobically oxidize both methane and reduced sulfur compounds for growth. Genomic and proteomic analyses showed that soluble methane monooxygenase and XoxF-type alcohol dehydrogenases are responsible for methane and methanol oxidation, respectively. Various pathways for respiratory sulfur oxidation were present, including the Sox–rDsr pathway and the S4I system. Strain HY1 employed the Calvin–Benson–Bassham cycle for CO2 fixation during chemolithoautotrophic growth on reduced sulfur compounds. Proteomic and microrespirometry analyses showed that the metabolic pathways for methane and thiosulfate oxidation were induced in the presence of the respective substrates. Methane and thiosulfate could therefore be independently or simultaneously oxidized. The discovery of this versatile bacterium demonstrates that methanotrophy and thiotrophy are compatible in a single microorganism and underpins the intimate interactions of methane and sulfur cycles in oxic–anoxic interface environments.
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8
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Ray AE, Zaugg J, Benaud N, Chelliah DS, Bay S, Wong HL, Leung PM, Ji M, Terauds A, Montgomery K, Greening C, Cowan DA, Kong W, Williams TJ, Hugenholtz P, Ferrari BC. Atmospheric chemosynthesis is phylogenetically and geographically widespread and contributes significantly to carbon fixation throughout cold deserts. THE ISME JOURNAL 2022; 16:2547-2560. [PMID: 35933499 PMCID: PMC9561532 DOI: 10.1038/s41396-022-01298-5] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/23/2022] [Revised: 07/05/2022] [Accepted: 07/15/2022] [Indexed: 11/24/2022]
Abstract
Cold desert soil microbiomes thrive despite severe moisture and nutrient limitations. In Eastern Antarctic soils, bacterial primary production is supported by trace gas oxidation and the light-independent RuBisCO form IE. This study aims to determine if atmospheric chemosynthesis is widespread within Antarctic, Arctic and Tibetan cold deserts, to identify the breadth of trace gas chemosynthetic taxa and to further characterize the genetic determinants of this process. H2 oxidation was ubiquitous, far exceeding rates reported to fulfill the maintenance needs of similarly structured edaphic microbiomes. Atmospheric chemosynthesis occurred globally, contributing significantly (p < 0.05) to carbon fixation in Antarctica and the high Arctic. Taxonomic and functional analyses were performed upon 18 cold desert metagenomes, 230 dereplicated medium-to-high-quality derived metagenome-assembled genomes (MAGs) and an additional 24,080 publicly available genomes. Hydrogenotrophic and carboxydotrophic growth markers were widespread. RuBisCO IE was discovered to co-occur alongside trace gas oxidation enzymes in representative Chloroflexota, Firmicutes, Deinococcota and Verrucomicrobiota genomes. We identify a novel group of high-affinity [NiFe]-hydrogenases, group 1m, through phylogenetics, gene structure analysis and homology modeling, and reveal substantial genetic diversity within RuBisCO form IE (rbcL1E), and high-affinity 1h and 1l [NiFe]-hydrogenase groups. We conclude that atmospheric chemosynthesis is a globally-distributed phenomenon, extending throughout cold deserts, with significant implications for the global carbon cycle and bacterial survival within environmental reservoirs.
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9
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Schmitz RA, Mohammadi SS, van Erven T, Berben T, Jetten MSM, Pol A, Op den Camp HJM. Methanethiol Consumption and Hydrogen Sulfide Production by the Thermoacidophilic Methanotroph Methylacidiphilum fumariolicum SolV. Front Microbiol 2022; 13:857442. [PMID: 35422776 PMCID: PMC9003020 DOI: 10.3389/fmicb.2022.857442] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2022] [Accepted: 02/28/2022] [Indexed: 11/13/2022] Open
Abstract
Methanotrophs aerobically oxidize methane to carbon dioxide to make a living and are known to degrade various other short chain carbon compounds as well. Volatile organic sulfur compounds such as methanethiol (CH3SH) are important intermediates in the sulfur cycle. Although volatile organic sulfur compounds co-occur with methane in various environments, little is known about how these compounds affect methanotrophy. The enzyme methanethiol oxidase catalyzing the oxidation of methanethiol has been known for decades, but only recently the mtoX gene encoding this enzyme was identified in a methylotrophic bacterium. The presence of a homologous gene in verrucomicrobial methanotrophs prompted us to examine how methanotrophs cope with methanethiol. Here, we show that the verrucomicrobial methanotroph Methylacidiphilum fumariolicum SolV consumes methanethiol and produces H2S, which is concurrently oxidized. Consumption of methanethiol is required since methanethiol inhibits methane oxidation. Cells incubated with ∼15 μM methanethiol from the start clearly showed inhibition of growth. After depletion of methanethiol, growth resumed within 1 day. Genes encoding a putative methanethiol oxidase were found in a variety of methanotrophs. Therefore, we hypothesize that methanethiol degradation is a widespread detoxification mechanism in methanotrophs in a range of environments.
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Affiliation(s)
- Rob A Schmitz
- Department of Microbiology, Radboud Institute for Biological and Environmental Research, Radboud University, Nijmegen, Netherlands.,Environmental Chemistry, Institute of Biogeochemistry and Pollutant Dynamics, ETH Zürich, Zurich, Switzerland
| | - Sepehr S Mohammadi
- Department of Microbiology, Radboud Institute for Biological and Environmental Research, Radboud University, Nijmegen, Netherlands
| | - Timo van Erven
- Department of Microbiology, Radboud Institute for Biological and Environmental Research, Radboud University, Nijmegen, Netherlands
| | - Tom Berben
- Department of Microbiology, Radboud Institute for Biological and Environmental Research, Radboud University, Nijmegen, Netherlands
| | - Mike S M Jetten
- Department of Microbiology, Radboud Institute for Biological and Environmental Research, Radboud University, Nijmegen, Netherlands
| | - Arjan Pol
- Department of Microbiology, Radboud Institute for Biological and Environmental Research, Radboud University, Nijmegen, Netherlands
| | - Huub J M Op den Camp
- Department of Microbiology, Radboud Institute for Biological and Environmental Research, Radboud University, Nijmegen, Netherlands
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10
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Oshkin IY, Danilova OV, But SY, Miroshnikov KK, Suleimanov RZ, Belova SE, Tikhonova EN, Kuznetsov NN, Khmelenina VN, Pimenov NV, Dedysh SN. Expanding Characterized Diversity and the Pool of Complete Genome Sequences of Methylococcus Species, the Bacteria of High Environmental and Biotechnological Relevance. Front Microbiol 2021; 12:756830. [PMID: 34691008 PMCID: PMC8527097 DOI: 10.3389/fmicb.2021.756830] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2021] [Accepted: 09/13/2021] [Indexed: 11/18/2022] Open
Abstract
The bacterial genus Methylococcus, which comprises aerobic thermotolerant methanotrophic cocci, was described half-a-century ago. Over the years, a member of this genus, Methylococcus capsulatus Bath, has become a major model organism to study genomic and metabolic basis of obligate methanotrophy. High biotechnological potential of fast-growing Methylococcus species, mainly as a promising source of feed protein, has also been recognized. Despite this big research attention, the currently cultured Methylococcus diversity is represented by members of the two species, M. capsulatus and M. geothermalis, while finished genome sequences are available only for two strains of these methanotrophs. This study extends the pool of phenotypically characterized Methylococcus strains with good-quality genome sequences by contributing four novel isolates of these bacteria from activated sludge, landfill cover soil, and freshwater sediments. The determined genome sizes of novel isolates varied between 3.2 and 4.0Mb. As revealed by the phylogenomic analysis, strains IO1, BH, and KN2 affiliate with M. capsulatus, while strain Mc7 may potentially represent a novel species. Highest temperature optima (45-50°C) and highest growth rates in bioreactor cultures (up to 0.3h-1) were recorded for strains obtained from activated sludge. The comparative analysis of all complete genomes of Methylococcus species revealed 4,485 gene clusters. Of these, pan-genome core comprised 2,331 genes (on average 51.9% of each genome), with the accessory genome containing 846 and 1,308 genes in the shell and the cloud, respectively. Independently of the isolation source, all strains of M. capsulatus displayed surprisingly high genome synteny and a striking similarity in gene content. Strain Mc7 from a landfill cover soil differed from other isolates by the high content of mobile genetic elements in the genome and a number of genome-encoded features missing in M. capsulatus, such as sucrose biosynthesis and the ability to scavenge phosphorus and sulfur from the environment.
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Affiliation(s)
- Igor Y. Oshkin
- Winogradsky Institute of Microbiology, Research Center of Biotechnology, Russian Academy of Sciences, Moscow, Russia
| | - Olga V. Danilova
- Winogradsky Institute of Microbiology, Research Center of Biotechnology, Russian Academy of Sciences, Moscow, Russia
| | - Sergey Y. But
- Winogradsky Institute of Microbiology, Research Center of Biotechnology, Russian Academy of Sciences, Moscow, Russia
- G. K. Skryabin Institute of Biochemistry and Physiology of Microorganisms, Pushchino Scientific Center for Biological Research, Russian Academy of Sciences, Pushchino, Russia
| | - Kirill K. Miroshnikov
- Winogradsky Institute of Microbiology, Research Center of Biotechnology, Russian Academy of Sciences, Moscow, Russia
| | - Ruslan Z. Suleimanov
- Winogradsky Institute of Microbiology, Research Center of Biotechnology, Russian Academy of Sciences, Moscow, Russia
| | - Svetlana E. Belova
- Winogradsky Institute of Microbiology, Research Center of Biotechnology, Russian Academy of Sciences, Moscow, Russia
| | - Ekaterina N. Tikhonova
- Winogradsky Institute of Microbiology, Research Center of Biotechnology, Russian Academy of Sciences, Moscow, Russia
| | - Nikolai N. Kuznetsov
- Winogradsky Institute of Microbiology, Research Center of Biotechnology, Russian Academy of Sciences, Moscow, Russia
| | - Valentina N. Khmelenina
- G. K. Skryabin Institute of Biochemistry and Physiology of Microorganisms, Pushchino Scientific Center for Biological Research, Russian Academy of Sciences, Pushchino, Russia
| | - Nikolai V. Pimenov
- Winogradsky Institute of Microbiology, Research Center of Biotechnology, Russian Academy of Sciences, Moscow, Russia
| | - Svetlana N. Dedysh
- Winogradsky Institute of Microbiology, Research Center of Biotechnology, Russian Academy of Sciences, Moscow, Russia
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11
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Kerckhof FM, Sakarika M, Van Giel M, Muys M, Vermeir P, De Vrieze J, Vlaeminck SE, Rabaey K, Boon N. From Biogas and Hydrogen to Microbial Protein Through Co-Cultivation of Methane and Hydrogen Oxidizing Bacteria. Front Bioeng Biotechnol 2021; 9:733753. [PMID: 34527661 PMCID: PMC8435580 DOI: 10.3389/fbioe.2021.733753] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Accepted: 08/13/2021] [Indexed: 01/23/2023] Open
Abstract
Increasing efforts are directed towards the development of sustainable alternative protein sources among which microbial protein (MP) is one of the most promising. Especially when waste streams are used as substrates, the case for MP could become environmentally favorable. The risks of using organic waste streams for MP production-the presence of pathogens or toxicants-can be mitigated by their anaerobic digestion and subsequent aerobic assimilation of the (filter-sterilized) biogas. Even though methane and hydrogen oxidizing bacteria (MOB and HOB) have been intensively studied for MP production, the potential benefits of their co-cultivation remain elusive. Here, we isolated a diverse group of novel HOB (that were capable of autotrophic metabolism), and co-cultured them with a defined set of MOB, which could be grown on a mixture of biogas and H2/O2. The combination of MOB and HOB, apart from the CH4 and CO2 contained in biogas, can also enable the valorization of the CO2 that results from the oxidation of methane by the MOB. Different MOB and HOB combinations were grown in serum vials to identify the best-performing ones. We observed synergistic effects on growth for several combinations, and in all combinations a co-culture consisting out of both HOB and MOB could be maintained during five days of cultivation. Relative to the axenic growth, five out of the ten co-cultures exhibited 1.1-3.8 times higher protein concentration and two combinations presented 2.4-6.1 times higher essential amino acid content. The MP produced in this study generally contained lower amounts of the essential amino acids histidine, lysine and threonine, compared to tofu and fishmeal. The most promising combination in terms of protein concentration and essential amino acid profile was Methyloparacoccus murrelli LMG 27482 with Cupriavidus necator LMG 1201. Microbial protein from M. murrelli and C. necator requires 27-67% less quantity than chicken, whole egg and tofu, while it only requires 15% more quantity than the amino acid-dense soybean to cover the needs of an average adult. In conclusion, while limitations still exist, the co-cultivation of MOB and HOB creates an alternative route for MP production leveraging safe and sustainably-produced gaseous substrates.
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Affiliation(s)
- Frederiek-Maarten Kerckhof
- Center for Microbial Ecology and Technology, Faculty of Bioscience Engineering, Ghent University, Gent, Belgium
- Center for Advanced Process Technology for Urban Resource Recovery (CAPTURE), Gent, Belgium
| | - Myrsini Sakarika
- Center for Microbial Ecology and Technology, Faculty of Bioscience Engineering, Ghent University, Gent, Belgium
- Center for Advanced Process Technology for Urban Resource Recovery (CAPTURE), Gent, Belgium
| | - Marie Van Giel
- Center for Microbial Ecology and Technology, Faculty of Bioscience Engineering, Ghent University, Gent, Belgium
| | - Maarten Muys
- Research Group of Sustainable Energy, Air and Water Technology, Department of Bioscience Engineering, University of Antwerp, Antwerpen, Belgium
| | - Pieter Vermeir
- Laboratory of Chemical Analysis, Department of Green Chemistry and Technology, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium
| | - Jo De Vrieze
- Center for Microbial Ecology and Technology, Faculty of Bioscience Engineering, Ghent University, Gent, Belgium
| | - Siegfried E. Vlaeminck
- Center for Advanced Process Technology for Urban Resource Recovery (CAPTURE), Gent, Belgium
- Research Group of Sustainable Energy, Air and Water Technology, Department of Bioscience Engineering, University of Antwerp, Antwerpen, Belgium
| | - Korneel Rabaey
- Center for Microbial Ecology and Technology, Faculty of Bioscience Engineering, Ghent University, Gent, Belgium
- Center for Advanced Process Technology for Urban Resource Recovery (CAPTURE), Gent, Belgium
| | - Nico Boon
- Center for Microbial Ecology and Technology, Faculty of Bioscience Engineering, Ghent University, Gent, Belgium
- Center for Advanced Process Technology for Urban Resource Recovery (CAPTURE), Gent, Belgium
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12
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Ribulose-1,5-Bisphosphate Carboxylase/Oxygenase (RubisCO) Is Essential for Growth of the Methanotroph Methylococcus capsulatus Strain Bath. Appl Environ Microbiol 2021; 87:e0088121. [PMID: 34288705 PMCID: PMC8388818 DOI: 10.1128/aem.00881-21] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
The ribulose-1,5-bisphosphate carboxylase/oxygenase (RubisCO) enzyme found in plants, algae, and an array of autotrophic bacteria is also encoded by a subset of methanotrophs, but its role in these microbes has largely remained elusive. In this study, we showed that CO2 was requisite for RubisCO-encoding Methylococcus capsulatus strain Bath growth in a bioreactor with continuous influent and effluent gas flow. RNA sequencing identified active transcription of several carboxylating enzymes, including key enzymes of the Calvin and serine cycles, that could mediate CO2 assimilation during cultivation with both CH4 and CO2 as carbon sources. Marker exchange mutagenesis of M. capsulatus Bath genes encoding key enzymes of potential CO2-assimilating metabolic pathways indicated that a complete serine cycle is not required, whereas RubisCO is essential for growth of this bacterium. 13CO2 tracer analysis showed that CH4 and CO2 enter overlapping anaplerotic pathways and implicated RubisCO as the primary enzyme mediating CO2 assimilation in M. capsulatus Bath. Notably, we quantified the relative abundance of 3-phosphoglycerate and ribulose-1,5-bisphosphate 13C isotopes, which supported that RubisCO-produced 3-phosphoglycerate is primarily converted to ribulose-1-5-bisphosphate via the oxidative pentose phosphate pathway in M. capsulatus Bath. Collectively, our data establish that RubisCO and CO2 play essential roles in M. capsulatus Bath metabolism. This study expands the known capacity of methanotrophs to fix CO2 via RubisCO, which may play a more pivotal role in the Earth's biogeochemical carbon cycling and greenhouse gas regulation than previously recognized. Further, M. capsulatus Bath and other CO2-assimilating methanotrophs represent excellent candidates for use in the bioconversion of biogas waste streams that consist of both CH4 and CO2. IMPORTANCE The importance of RubisCO and CO2 in M. capsulatus Bath metabolism is unclear. In this study, we demonstrated that both CO2 and RubisCO are essential for M. capsulatus Bath growth. 13CO2 tracing experiments supported that RubisCO mediates CO2 fixation and that a noncanonical Calvin cycle is active in this organism. Our study provides insights into the expanding knowledge of methanotroph metabolism and implicates dually CH4/CO2-utilizing bacteria as more important players in the biogeochemical carbon cycle than previously appreciated. In addition, M. capsulatus and other methanotrophs with CO2 assimilation capacity represent candidate organisms for the development of biotechnologies to mitigate the two most abundant greenhouse gases, CH4 and CO2.
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13
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Carere CR, Hards K, Wigley K, Carman L, Houghton KM, Cook GM, Stott MB. Growth on Formic Acid Is Dependent on Intracellular pH Homeostasis for the Thermoacidophilic Methanotroph Methylacidiphilum sp. RTK17.1. Front Microbiol 2021; 12:651744. [PMID: 33841379 PMCID: PMC8024496 DOI: 10.3389/fmicb.2021.651744] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2021] [Accepted: 02/22/2021] [Indexed: 12/13/2022] Open
Abstract
Members of the genus Methylacidiphilum, a clade of metabolically flexible thermoacidophilic methanotrophs from the phylum Verrucomicrobia, can utilize a variety of substrates including methane, methanol, and hydrogen for growth. However, despite sequentially oxidizing methane to carbon dioxide via methanol and formate intermediates, growth on formate as the only source of reducing equivalents (i.e., NADH) has not yet been demonstrated. In many acidophiles, the inability to grow on organic acids has presumed that diffusion of the protonated form (e.g., formic acid) into the cell is accompanied by deprotonation prompting cytosolic acidification, which leads to the denaturation of vital proteins and the collapse of the proton motive force. In this work, we used a combination of biochemical, physiological, chemostat, and transcriptomic approaches to demonstrate that Methylacidiphilum sp. RTK17.1 can utilize formate as a substrate when cells are able to maintain pH homeostasis. Our findings show that Methylacidiphilum sp. RTK17.1 grows optimally with a circumneutral intracellular pH (pH 6.52 ± 0.04) across an extracellular range of pH 1.5–3.0. In batch experiments, formic acid addition resulted in no observable cell growth and cell death due to acidification of the cytosol. Nevertheless, stable growth on formic acid as the only source of energy was demonstrated in continuous chemostat cultures (D = 0.0052 h−1, td = 133 h). During growth on formic acid, biomass yields remained nearly identical to methanol-grown chemostat cultures when normalized per mole electron equivalent. Transcriptome analysis revealed the key genes associated with stress response: methane, methanol, and formate metabolism were differentially expressed in response to growth on formic acid. Collectively, these results show formic acid represents a utilizable source of energy/carbon to the acidophilic methanotrophs within geothermal environments. Findings expand the known metabolic flexibility of verrucomicrobial methanotrophs to include organic acids and provide insight into potential survival strategies used by these species during methane starvation.
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Affiliation(s)
- Carlo R Carere
- Department of Chemical and Process Engineering, University of Canterbury, Christchurch, New Zealand
| | - Kiel Hards
- Department of Microbiology and Immunology, University of Otago, Dunedin, New Zealand.,Maurice Wilkins Center for Molecular Biodiscovery, Auckland, New Zealand
| | - Kathryn Wigley
- Department of Chemical and Process Engineering, University of Canterbury, Christchurch, New Zealand
| | - Luke Carman
- Department of Chemical and Process Engineering, University of Canterbury, Christchurch, New Zealand
| | - Karen M Houghton
- Geomicrobiology Research Group, Department of Geothermal Sciences, GNS Science, Taupō, New Zealand
| | - Gregory M Cook
- Department of Microbiology and Immunology, University of Otago, Dunedin, New Zealand.,Maurice Wilkins Center for Molecular Biodiscovery, Auckland, New Zealand
| | - Matthew B Stott
- School of Biological Sciences, University of Canterbury, Christchurch, New Zealand
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14
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Ghezzi D, Sauro F, Columbu A, Carbone C, Hong PY, Vergara F, De Waele J, Cappelletti M. Transition from unclassified Ktedonobacterales to Actinobacteria during amorphous silica precipitation in a quartzite cave environment. Sci Rep 2021; 11:3921. [PMID: 33594175 PMCID: PMC7887251 DOI: 10.1038/s41598-021-83416-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2020] [Accepted: 01/27/2021] [Indexed: 01/31/2023] Open
Abstract
The orthoquartzite Imawarì Yeuta cave hosts exceptional silica speleothems and represents a unique model system to study the geomicrobiology associated to silica amorphization processes under aphotic and stable physical-chemical conditions. In this study, three consecutive evolution steps in the formation of a peculiar blackish coralloid silica speleothem were studied using a combination of morphological, mineralogical/elemental and microbiological analyses. Microbial communities were characterized using Illumina sequencing of 16S rRNA gene and clone library analysis of carbon monoxide dehydrogenase (coxL) and hydrogenase (hypD) genes involved in atmospheric trace gases utilization. The first stage of the silica amorphization process was dominated by members of a still undescribed microbial lineage belonging to the Ktedonobacterales order, probably involved in the pioneering colonization of quartzitic environments. Actinobacteria of the Pseudonocardiaceae and Acidothermaceae families dominated the intermediate amorphous silica speleothem and the final coralloid silica speleothem, respectively. The atmospheric trace gases oxidizers mostly corresponded to the main bacterial taxa present in each speleothem stage. These results provide novel understanding of the microbial community structure accompanying amorphization processes and of coxL and hypD gene expression possibly driving atmospheric trace gases metabolism in dark oligotrophic caves.
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Affiliation(s)
- D. Ghezzi
- grid.6292.f0000 0004 1757 1758Department of Pharmacy and Biotechnology, University of Bologna, 40126 Bologna, Italy ,grid.419038.70000 0001 2154 6641Laboratory of NanoBiotechnology, IRCCS Istituto Ortopedico Rizzoli, 40136 Bologna, Italy
| | - F. Sauro
- grid.6292.f0000 0004 1757 1758Department of Biological Geological and Environmental Sciences, University of Bologna, 40126 Bologna, Italy ,La Venta Geographic Explorations Association, 31100 Treviso, Italy ,Teraphosa Exploring Team, Puerto Ordaz, Venezuela
| | - A. Columbu
- grid.6292.f0000 0004 1757 1758Department of Biological Geological and Environmental Sciences, University of Bologna, 40126 Bologna, Italy
| | - C. Carbone
- grid.5606.50000 0001 2151 3065Department of Earth, Environment and Life, University of Genoa, 16132 Genoa, Italy
| | - P.-Y. Hong
- grid.45672.320000 0001 1926 5090Division of Biological and Environmental Science and Engineering, King Abdullah University of Science and Technology (KAUST), Thuwal, 23955-6900 Saudi Arabia
| | - F. Vergara
- La Venta Geographic Explorations Association, 31100 Treviso, Italy ,Teraphosa Exploring Team, Puerto Ordaz, Venezuela
| | - J. De Waele
- grid.6292.f0000 0004 1757 1758Department of Biological Geological and Environmental Sciences, University of Bologna, 40126 Bologna, Italy
| | - M. Cappelletti
- grid.6292.f0000 0004 1757 1758Department of Pharmacy and Biotechnology, University of Bologna, 40126 Bologna, Italy
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15
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Picone N, Blom P, Wallenius AJ, Hogendoorn C, Mesman R, Cremers G, Gagliano AL, D'Alessandro W, Quatrini P, Jetten MSM, Pol A, Op den Camp HJM. Methylacidimicrobium thermophilum AP8, a Novel Methane- and Hydrogen-Oxidizing Bacterium Isolated From Volcanic Soil on Pantelleria Island, Italy. Front Microbiol 2021; 12:637762. [PMID: 33643272 PMCID: PMC7907005 DOI: 10.3389/fmicb.2021.637762] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2020] [Accepted: 01/25/2021] [Indexed: 11/13/2022] Open
Abstract
The Favara Grande is a geothermal area located on Pantelleria Island, Italy. The area is characterized high temperatures in the top layer of the soil (60°C), low pH (3–5) and hydrothermal gas emissions mainly composed of carbon dioxide (CO2), methane (CH4), and hydrogen (H2). These geothermal features may provide a suitable niche for the growth of chemolithotrophic thermoacidophiles, including the lanthanide-dependent methanotrophs of the phylum Verrucomicrobia. In this study, we started enrichment cultures inoculated with soil of the Favara Grande at 50 and 60°C with CH4 as energy source and medium containing sufficient lanthanides at pH 3 and 5. From these cultures, a verrucomicrobial methanotroph could be isolated via serial dilution and floating filters techniques. The genome of strain AP8 was sequenced and based on phylogenetic analysis we propose to name this new species Methylacidimicrobium thermophilum AP8. The transcriptome data at μmax (0.051 ± 0.001 h−1, doubling time ~14 h) of the new strain showed a high expression of the pmoCAB2 operon encoding the membrane-bound methane monooxygenase and of the gene xoxF1, encoding the lanthanide-dependent methanol dehydrogenase. A second pmoCAB operon and xoxF2 gene were not expressed. The physiology of strain AP8 was further investigated and revealed an optimal growth in a pH range of 3–5 at 50°C, representing the first thermophilic strain of the genus Methylacidimicrobium. Moreover, strain AP8 had a KS(app) for methane of 8 ± 1 μM. Beside methane, a type 1b [NiFe] hydrogenase enabled hydrogen oxidation at oxygen concentrations up to 1%. Taken together, our results expand the knowledge on the characteristics and adaptations of verrucomicrobial methanotrophs in hydrothermal environments and add a new thermophilic strain to the genus Methylacidimicrobium.
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Affiliation(s)
- Nunzia Picone
- Department of Microbiology, Institute for Water and Wetland Research, Radboud University, Nijmegen, Netherlands
| | - Pieter Blom
- Department of Microbiology, Institute for Water and Wetland Research, Radboud University, Nijmegen, Netherlands
| | - Anna J Wallenius
- Department of Microbiology, Institute for Water and Wetland Research, Radboud University, Nijmegen, Netherlands
| | - Carmen Hogendoorn
- Department of Microbiology, Institute for Water and Wetland Research, Radboud University, Nijmegen, Netherlands
| | - Rob Mesman
- Department of Microbiology, Institute for Water and Wetland Research, Radboud University, Nijmegen, Netherlands
| | - Geert Cremers
- Department of Microbiology, Institute for Water and Wetland Research, Radboud University, Nijmegen, Netherlands
| | | | | | - Paola Quatrini
- Department of Biological, Chemical and Pharmaceutical Sciences and Technologies (STEBICEF), University of Palermo, Palermo, Italy
| | - Mike S M Jetten
- Department of Microbiology, Institute for Water and Wetland Research, Radboud University, Nijmegen, Netherlands
| | - Arjan Pol
- Department of Microbiology, Institute for Water and Wetland Research, Radboud University, Nijmegen, Netherlands
| | - Huub J M Op den Camp
- Department of Microbiology, Institute for Water and Wetland Research, Radboud University, Nijmegen, Netherlands
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16
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Schmitz RA, Peeters SH, Versantvoort W, Picone N, Pol A, Jetten MSM, Op den Camp HJM. Verrucomicrobial methanotrophs: ecophysiology of metabolically versatile acidophiles. FEMS Microbiol Rev 2021; 45:6125968. [PMID: 33524112 PMCID: PMC8498564 DOI: 10.1093/femsre/fuab007] [Citation(s) in RCA: 33] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2020] [Accepted: 01/15/2021] [Indexed: 12/26/2022] Open
Abstract
Methanotrophs are an important group of microorganisms that counteract methane emissions to the atmosphere. Methane-oxidising bacteria of the Alpha- and Gammaproteobacteria have been studied for over a century, while methanotrophs of the phylum Verrucomicrobia are a more recent discovery. Verrucomicrobial methanotrophs are extremophiles that live in very acidic geothermal ecosystems. Currently, more than a dozen strains have been isolated, belonging to the genera Methylacidiphilum and Methylacidimicrobium. Initially, these methanotrophs were thought to be metabolically confined. However, genomic analyses and physiological and biochemical experiments over the past years revealed that verrucomicrobial methanotrophs, as well as proteobacterial methanotrophs, are much more metabolically versatile than previously assumed. Several inorganic gases and other molecules present in acidic geothermal ecosystems can be utilised, such as methane, hydrogen gas, carbon dioxide, ammonium, nitrogen gas and perhaps also hydrogen sulfide. Verrucomicrobial methanotrophs could therefore represent key players in multiple volcanic nutrient cycles and in the mitigation of greenhouse gas emissions from geothermal ecosystems. Here, we summarise the current knowledge on verrucomicrobial methanotrophs with respect to their metabolic versatility and discuss the factors that determine their diversity in their natural environment. In addition, key metabolic, morphological and ecological characteristics of verrucomicrobial and proteobacterial methanotrophs are reviewed.
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Affiliation(s)
- Rob A Schmitz
- Department of Microbiology, Institute for Water and Wetland Research, Radboud University, Heyendaalseweg 135, 6525 AJ, Nijmegen, The Netherlands
| | - Stijn H Peeters
- Department of Microbiology, Institute for Water and Wetland Research, Radboud University, Heyendaalseweg 135, 6525 AJ, Nijmegen, The Netherlands
| | - Wouter Versantvoort
- Department of Microbiology, Institute for Water and Wetland Research, Radboud University, Heyendaalseweg 135, 6525 AJ, Nijmegen, The Netherlands
| | - Nunzia Picone
- Department of Microbiology, Institute for Water and Wetland Research, Radboud University, Heyendaalseweg 135, 6525 AJ, Nijmegen, The Netherlands
| | - Arjan Pol
- Department of Microbiology, Institute for Water and Wetland Research, Radboud University, Heyendaalseweg 135, 6525 AJ, Nijmegen, The Netherlands
| | - Mike S M Jetten
- Department of Microbiology, Institute for Water and Wetland Research, Radboud University, Heyendaalseweg 135, 6525 AJ, Nijmegen, The Netherlands
| | - Huub J M Op den Camp
- Department of Microbiology, Institute for Water and Wetland Research, Radboud University, Heyendaalseweg 135, 6525 AJ, Nijmegen, The Netherlands
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17
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Kucera J, Lochman J, Bouchal P, Pakostova E, Mikulasek K, Hedrich S, Janiczek O, Mandl M, Johnson DB. A Model of Aerobic and Anaerobic Metabolism of Hydrogen in the Extremophile Acidithiobacillus ferrooxidans. Front Microbiol 2020; 11:610836. [PMID: 33329503 PMCID: PMC7735108 DOI: 10.3389/fmicb.2020.610836] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2020] [Accepted: 11/04/2020] [Indexed: 12/12/2022] Open
Abstract
Hydrogen can serve as an electron donor for chemolithotrophic acidophiles, especially in the deep terrestrial subsurface and geothermal ecosystems. Nevertheless, the current knowledge of hydrogen utilization by mesophilic acidophiles is minimal. A multi-omics analysis was applied on Acidithiobacillus ferrooxidans growing on hydrogen, and a respiratory model was proposed. In the model, [NiFe] hydrogenases oxidize hydrogen to two protons and two electrons. The electrons are used to reduce membrane-soluble ubiquinone to ubiquinol. Genetically associated iron-sulfur proteins mediate electron relay from the hydrogenases to the ubiquinone pool. Under aerobic conditions, reduced ubiquinol transfers electrons to either cytochrome aa 3 oxidase via cytochrome bc 1 complex and cytochrome c 4 or the alternate directly to cytochrome bd oxidase, resulting in proton efflux and reduction of oxygen. Under anaerobic conditions, reduced ubiquinol transfers electrons to outer membrane cytochrome c (ferrireductase) via cytochrome bc 1 complex and a cascade of electron transporters (cytochrome c 4, cytochrome c 552, rusticyanin, and high potential iron-sulfur protein), resulting in proton efflux and reduction of ferric iron. The proton gradient generated by hydrogen oxidation maintains the membrane potential and allows the generation of ATP and NADH. These results further clarify the role of extremophiles in biogeochemical processes and their impact on the composition of the deep terrestrial subsurface.
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Affiliation(s)
- Jiri Kucera
- Department of Biochemistry, Faculty of Science, Masaryk University, Brno, Czechia
| | - Jan Lochman
- Department of Biochemistry, Faculty of Science, Masaryk University, Brno, Czechia
| | - Pavel Bouchal
- Department of Biochemistry, Faculty of Science, Masaryk University, Brno, Czechia
| | - Eva Pakostova
- School of Biological Sciences, College of Natural Sciences, Bangor University, Bangor, United Kingdom
| | - Kamil Mikulasek
- Mendel Centre for Plant Genomics and Proteomics, Central European Institute of Technology, Brno, Czechia
| | - Sabrina Hedrich
- Institute of Biosciences, Technische Universität (TU) Bergakademie Freiberg, Freiberg, Germany
| | - Oldrich Janiczek
- Department of Biochemistry, Faculty of Science, Masaryk University, Brno, Czechia
| | - Martin Mandl
- Department of Biochemistry, Faculty of Science, Masaryk University, Brno, Czechia
| | - D Barrie Johnson
- School of Biological Sciences, College of Natural Sciences, Bangor University, Bangor, United Kingdom
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18
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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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Farhan Ul Haque M, Xu HJ, Murrell JC, Crombie A. Facultative methanotrophs - diversity, genetics, molecular ecology and biotechnological potential: a mini-review. MICROBIOLOGY (READING, ENGLAND) 2020; 166:894-908. [PMID: 33085587 PMCID: PMC7660913 DOI: 10.1099/mic.0.000977] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/15/2020] [Accepted: 09/20/2020] [Indexed: 12/18/2022]
Abstract
Methane-oxidizing bacteria (methanotrophs) play a vital role in reducing atmospheric methane emissions, and hence mitigating their potent global warming effects. A significant proportion of the methane released is thermogenic natural gas, containing associated short-chain alkanes as well as methane. It was one hundred years following the description of methanotrophs that facultative strains were discovered and validly described. These can use some multi-carbon compounds in addition to methane, often small organic acids, such as acetate, or ethanol, although Methylocella strains can also use short-chain alkanes, presumably deriving a competitive advantage from this metabolic versatility. Here, we review the diversity and molecular ecology of facultative methanotrophs. We discuss the genetic potential of the known strains and outline the consequent benefits they may obtain. Finally, we review the biotechnological promise of these fascinating microbes.
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Affiliation(s)
| | - Hui-Juan Xu
- School of Environmental Sciences, University of East Anglia, Norwich, NR4 7TJ, UK
- Present address: Joint Institute for Environmental Research & Education, College of Natural Resources and Environment, South China Agricultural University, Guangzhou 510642, PR China
| | - J. Colin Murrell
- School of Environmental Sciences, University of East Anglia, Norwich, NR4 7TJ, UK
| | - Andrew Crombie
- School of Biological Sciences, University of East Anglia, Norwich, NR4 7TJ, UK
- Present address: School of Environmental Sciences, University of East Anglia, Norwich, NR4 7TJ, UK
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Meruvu H, Wu H, Jiao Z, Wang L, Fei Q. From nature to nurture: Essence and methods to isolate robust methanotrophic bacteria. Synth Syst Biotechnol 2020; 5:173-178. [PMID: 32637670 PMCID: PMC7327766 DOI: 10.1016/j.synbio.2020.06.007] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2020] [Revised: 06/03/2020] [Accepted: 06/18/2020] [Indexed: 02/07/2023] Open
Abstract
Methanotrophic bacteria are entities with innate biocatalytic potential to biofilter and oxidize methane into simpler compounds concomitantly conserving energy, which can contribute to copious industrial applications. The future and efficacy of such industrial applications relies upon acquiring and/or securing robust methanotrophs with taxonomic and phenotypic diversity. Despite several dramatic advances, isolation of robust methanotrophs is still a long-way challenging task with several lacunae to be filled in sequentially. Methanotrophs with high tolerance to methane can be isolated and cultivated by mimicking natural environs, and adopting strategies like adaptive metabolic evolution. This review summarizes existent and innovative methods for methanotrophic isolation and purification, and their respective applications. A comprehensive description of new insights shedding light upon how to isolate and concomitantly augment robust methanotrophic metabolism in an orchestrated fashion follows.
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Affiliation(s)
- Haritha Meruvu
- School of Chemical Engineering and Technology, Xi'an Jiaotong University, Xi'an, Shaanxi, China
| | - Hui Wu
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai, China
| | - Ziyue Jiao
- School of Chemical Engineering and Technology, Xi'an Jiaotong University, Xi'an, Shaanxi, China
| | - Liyan Wang
- Luoyang TMAXTREE Biotechnology Co., Ltd., Luoyang, China
| | - Qiang Fei
- School of Chemical Engineering and Technology, Xi'an Jiaotong University, Xi'an, Shaanxi, China
- Shaanxi Key Laboratory of Energy Chemical Process Intensification, Xi'an Jiaotong University, Xi'an, China
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Methanol Production by " Methylacidiphilum fumariolicum" SolV under Different Growth Conditions. Appl Environ Microbiol 2020; 86:AEM.01188-20. [PMID: 32631865 PMCID: PMC7480378 DOI: 10.1128/aem.01188-20] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2020] [Accepted: 06/30/2020] [Indexed: 12/13/2022] Open
Abstract
The production of methanol, an important chemical, is completely dependent on natural gas. The current multistep chemical process uses high temperature and pressure to convert methane in natural gas to methanol. In this study, we used the methanotroph “Methylacidiphilum fumariolicum” SolV to achieve continuous methanol production from methane as the substrate. The production rate was highly dependent on the growth rate of this microorganism, and high conversion efficiencies were obtained. Using microorganisms for the production of methanol might enable the use of more sustainable sources of methane, such as biogas, rather than natural gas. Industrial methanol production converts methane from natural gas into methanol through a multistep chemical process. Biological methane-to-methanol conversion under moderate conditions and using biogas would be more environmentally friendly. Methanotrophs, bacteria that use methane as an energy source, convert methane into methanol in a single step catalyzed by the enzyme methane monooxygenase, but inhibition of methanol dehydrogenase, which catalyzes the subsequent conversion of methanol into formaldehyde, is a major challenge. In this study, we used the thermoacidophilic methanotroph “Methylacidiphilum fumariolicum” SolV for biological methanol production. This bacterium possesses a XoxF-type methanol dehydrogenase that is dependent on rare earth elements for activity. By using a cultivation medium nearly devoid of lanthanides, we reduced methanol dehydrogenase activity and obtained a continuous methanol-producing microbial culture. The methanol production rate and conversion efficiency were growth-rate dependent. A maximal conversion efficiency of 63% mol methanol produced per mol methane consumed was obtained at a relatively high growth rate, with a methanol production rate of 0.88 mmol/g (dry weight)/h. This study demonstrates that methanotrophs can be used for continuous methanol production. Full-scale application will require additional increases in the titer, production rate, and efficiency, which can be achieved by further decreasing the lanthanide concentration through the use of increased biomass concentrations and novel reactor designs to supply sufficient gases, including methane, oxygen, and hydrogen. IMPORTANCE The production of methanol, an important chemical, is completely dependent on natural gas. The current multistep chemical process uses high temperature and pressure to convert methane in natural gas to methanol. In this study, we used the methanotroph “Methylacidiphilum fumariolicum” SolV to achieve continuous methanol production from methane as the substrate. The production rate was highly dependent on the growth rate of this microorganism, and high conversion efficiencies were obtained. Using microorganisms for the production of methanol might enable the use of more sustainable sources of methane, such as biogas, rather than natural gas.
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Islam MM, Le T, Daggumati SR, Saha R. Investigation of microbial community interactions between Lake Washington methanotrophs using -------genome-scale metabolic modeling. PeerJ 2020; 8:e9464. [PMID: 32655999 PMCID: PMC7333651 DOI: 10.7717/peerj.9464] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2020] [Accepted: 06/10/2020] [Indexed: 11/21/2022] Open
Abstract
Background The role of methane in global warming has become paramount to the environment and the human society, especially in the past few decades. Methane cycling microbial communities play an important role in the global methane cycle, which is why the characterization of these communities is critical to understand and manipulate their behavior. Methanotrophs are a major player in these communities and are able to oxidize methane as their primary carbon source. Results Lake Washington is a freshwater lake characterized by a methane-oxygen countergradient that contains a methane cycling microbial community. Methanotrophs are a major part of this community involved in assimilating methane from lake water. Two significant methanotrophic species in this community are Methylobacter and Methylomonas. In this work, these methanotrophs are computationally studied via developing highly curated genome-scale metabolic models. Each model was then integrated to form a community model with a multi-level optimization framework. The competitive and mutualistic metabolic interactions among Methylobacter and Methylomonas were also characterized. The community model was next tested under carbon, oxygen, and nitrogen limited conditions in addition to a nutrient-rich condition to observe the systematic shifts in the internal metabolic pathways and extracellular metabolite exchanges. Each condition showed variations in the methane oxidation pathway, pyruvate metabolism, and the TCA cycle as well as the excretion of formaldehyde and carbon di-oxide in the community. Finally, the community model was simulated under fixed ratios of these two members to reflect the opposing behavior in the two-member synthetic community and in sediment-incubated communities. The community simulations predicted a noticeable switch in intracellular carbon metabolism and formaldehyde transfer between community members in sediment-incubated vs. synthetic condition. Conclusion In this work, we attempted to predict the response of a simplified methane cycling microbial community from Lake Washington to varying environments and also provide an insight into the difference of dynamics in sediment-incubated microcosm community and synthetic co-cultures. Overall, this study lays the ground for in silico systems-level studies of freshwater lake ecosystems, which can drive future efforts of understanding, engineering, and modifying these communities for dealing with global warming issues.
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Affiliation(s)
- Mohammad Mazharul Islam
- Department of Chemical and Biomolecular Engineering, University of Nebraska-Lincoln, Lincoln, NE, United States of America
| | - Tony Le
- Department of Biochemistry, University of Nebraska-Lincoln, Lincoln, NE, United States of America
| | - Shardhat R Daggumati
- Department of Chemical and Biomolecular Engineering, University of Nebraska-Lincoln, Lincoln, NE, United States of America
| | - Rajib Saha
- Department of Chemical and Biomolecular Engineering, University of Nebraska-Lincoln, Lincoln, NE, United States of America
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Draft Genome Sequences of Two Acidophilic, Mesophilic Verrucomicrobial Methanotrophs Contain Only One pmoCAB Operon. Microbiol Resour Announc 2020; 9:9/16/e00315-20. [PMID: 32299887 PMCID: PMC7163025 DOI: 10.1128/mra.00315-20] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Methylacidimicrobium cyclopophantes 3B and Methylacidimicrobium tartarophylax 4AC are Gram-negative rod-shaped mesophilic methanotrophs isolated from soil samples with low pH at the Solfatara Crater, near Naples, Italy. The genomes of these extremophilic verrucomicrobia were sequenced using Illumina technology, and both species possess one pmoCAB operon and two xoxF genes.
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