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Li B, Mao Z, Xue J, Xing P, Wu QL. Metabolic versatility of aerobic methane-oxidizing bacteria under anoxia in aquatic ecosystems. ENVIRONMENTAL MICROBIOLOGY REPORTS 2024; 16:e70002. [PMID: 39232853 PMCID: PMC11374530 DOI: 10.1111/1758-2229.70002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/23/2024] [Accepted: 07/26/2024] [Indexed: 09/06/2024]
Abstract
The potential positive feedback between global aquatic deoxygenation and methane (CH4) emission emphasizes the importance of understanding CH4 cycling under O2-limited conditions. Increasing observations for aerobic CH4-oxidizing bacteria (MOB) under anoxia have updated the prevailing paradigm that MOB are O2-dependent; thus, clarification on the metabolic mechanisms of MOB under anoxia is critical and timely. Here, we mapped the global distribution of MOB under anoxic aquatic zones and summarized four underlying metabolic strategies for MOB under anoxia: (a) forming a consortium with oxygenic microorganisms; (b) self-generation/storage of O2 by MOB; (c) forming a consortium with non-oxygenic heterotrophic bacteria that use other electron acceptors; and (d) utilizing alternative electron acceptors other than O2. Finally, we proposed directions for future research. This study calls for improved understanding of MOB under anoxia, and underscores the importance of this overlooked CH4 sink amidst global aquatic deoxygenation.
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Affiliation(s)
- Biao Li
- Key Laboratory of Lake and Watershed Science for Water Security, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing, China
- State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing, China
| | - Zhendu Mao
- Center for Evolution and Conservation Biology, Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou, China
| | - Jingya Xue
- School of Geographical Sciences, Nanjing Normal University, Nanjing, China
| | - Peng Xing
- Key Laboratory of Lake and Watershed Science for Water Security, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing, China
- State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing, China
| | - Qinglong L Wu
- Key Laboratory of Lake and Watershed Science for Water Security, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing, China
- State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing, China
- Center for Evolution and Conservation Biology, Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou, China
- Sino-Danish Center for Education and Research, University of Chinese Academy of Sciences, Beijing, China
- The Fuxianhu Station of Plateau Deep Lake Research, Chinese Academy of Sciences, Yuxi, China
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2
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Colman DR, Keller LM, Arteaga-Pozo E, Andrade-Barahona E, St Clair B, Shoemaker A, Cox A, Boyd ES. Covariation of hot spring geochemistry with microbial genomic diversity, function, and evolution. Nat Commun 2024; 15:7506. [PMID: 39209850 PMCID: PMC11362583 DOI: 10.1038/s41467-024-51841-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2023] [Accepted: 08/20/2024] [Indexed: 09/04/2024] Open
Abstract
The geosphere and the microbial biosphere have co-evolved for ~3.8 Ga, with many lines of evidence suggesting a hydrothermal habitat for life's origin. However, the extent that contemporary thermophiles and their hydrothermal habitats reflect those that likely existed on early Earth remains unknown. To address this knowledge gap, 64 geochemical analytes were measured and 1022 metagenome-assembled-genomes (MAGs) were generated from 34 chemosynthetic high-temperature springs in Yellowstone National Park and analysed alongside 444 MAGs from 35 published metagenomes. We used these data to evaluate co-variation in MAG taxonomy, metabolism, and phylogeny as a function of hot spring geochemistry. We found that cohorts of MAGs and their functions are discretely distributed across pH gradients that reflect different geochemical provinces. Acidic or circumneutral/alkaline springs harbor MAGs that branched later and are enriched in sulfur- and arsenic-based O2-dependent metabolic pathways that are inconsistent with early Earth conditions. In contrast, moderately acidic springs sourced by volcanic gas harbor earlier-branching MAGs that are enriched in anaerobic, gas-dependent metabolisms (e.g. H2, CO2, CH4 metabolism) that have been hypothesized to support early microbial life. Our results provide insight into the influence of redox state in the eco-evolutionary feedbacks between thermophiles and their habitats and suggest moderately acidic springs as early Earth analogs.
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Affiliation(s)
- Daniel R Colman
- Department of Microbiology and Cell Biology, Montana State University, Bozeman, MT, USA.
| | - Lisa M Keller
- Department of Microbiology and Cell Biology, Montana State University, Bozeman, MT, USA
| | - Emilia Arteaga-Pozo
- Department of Chemistry and Geochemistry, Montana Technological University, Butte, MT, USA
| | - Eva Andrade-Barahona
- Department of Chemistry and Geochemistry, Montana Technological University, Butte, MT, USA
| | - Brian St Clair
- Department of Chemistry and Geochemistry, Montana Technological University, Butte, MT, USA
| | - Anna Shoemaker
- Department of Earth Sciences, Montana State University, Bozeman, MT, USA
| | - Alysia Cox
- Department of Chemistry and Geochemistry, Montana Technological University, Butte, MT, USA
| | - Eric S Boyd
- Department of Microbiology and Cell Biology, Montana State University, Bozeman, MT, USA.
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3
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Marshall IPG. Electromicrobiological concentration cells are an overlooked potential energy conservation mechanism for subsurface microorganisms. Front Microbiol 2024; 15:1407868. [PMID: 39234547 PMCID: PMC11371792 DOI: 10.3389/fmicb.2024.1407868] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2024] [Accepted: 08/05/2024] [Indexed: 09/06/2024] Open
Abstract
Thermodynamics has predicted many different kinds of microbial metabolism by determining which pairs of electron acceptors and donors will react to produce an exergonic reaction (a negative net change in Gibbs free energy). In energy-limited environments, such as the deep subsurface, such an approach can reveal the potential for unexpected or counter-intuitive energy sources for microbial metabolism. Up until recently, these thermodynamic calculations have been carried out with the assumption that chemical species appearing on the reactant and product side of a reaction formula have a constant concentration, and thus do not count towards net concentration changes and the overall direction of the reaction. This assumption is reasonable considering microorganisms are too small (~1 μm) for any significant differences in concentration to overcome diffusion. However, recent discoveries have demonstrated that the reductive and oxidative halves of reactions can be separated by much larger distances, from millimetres to centimetres via conductive filamentous bacteria, mineral conductivity, and biofilm conductivity. This means that the concentrations of reactants and products can indeed be different, and that concentration differences can contribute to the net negative change in Gibbs free energy. It even means that the same redox reaction, simultaneously running in forward and reverse, can drive energy conservation, in an ElectroMicrobiological Concentration Cell (EMCC). This paper presents a model to investigate this phenomenon and predict under which circumstances such concentration-driven metabolism might take place. The specific cases of oxygen concentration cells, sulfide concentration cells, and hydrogen concentration cells are examined in more detail.
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Affiliation(s)
- Ian P G Marshall
- Center for Electromicrobiology, Department of Biology, Aarhus University, Aarhus, Denmark
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4
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Schorn S, Graf JS, Littmann S, Hach PF, Lavik G, Speth DR, Schubert CJ, Kuypers MMM, Milucka J. Persistent activity of aerobic methane-oxidizing bacteria in anoxic lake waters due to metabolic versatility. Nat Commun 2024; 15:5293. [PMID: 38906896 PMCID: PMC11192741 DOI: 10.1038/s41467-024-49602-5] [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] [Received: 09/18/2023] [Accepted: 06/07/2024] [Indexed: 06/23/2024] Open
Abstract
Lacustrine methane emissions are strongly mitigated by aerobic methane-oxidizing bacteria (MOB) that are typically most active at the oxic-anoxic interface. Although oxygen is required by the MOB for the first step of methane oxidation, their occurrence in anoxic lake waters has raised the possibility that they are capable of oxidizing methane further anaerobically. Here, we investigate the activity and growth of MOB in Lake Zug, a permanently stratified freshwater lake. The rates of anaerobic methane oxidation in the anoxic hypolimnion reached up to 0.2 µM d-1. Single-cell nanoSIMS measurements, together with metagenomic and metatranscriptomic analyses, linked the measured rates to MOB of the order Methylococcales. Interestingly, their methane assimilation activity was similar under hypoxic and anoxic conditions. Our data suggest that these MOB use fermentation-based methanotrophy as well as denitrification under anoxic conditions, thus offering an explanation for their widespread presence in anoxic habitats such as stratified water columns. Thus, the methane sink capacity of anoxic basins may have been underestimated by not accounting for the anaerobic MOB activity.
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Affiliation(s)
- Sina Schorn
- Max Planck Institute for Marine Microbiology, Bremen, Germany.
- Department of Marine Sciences, University of Gothenburg, Gothenburg, Sweden.
| | - Jon S Graf
- Max Planck Institute for Marine Microbiology, Bremen, Germany
| | - Sten Littmann
- Max Planck Institute for Marine Microbiology, Bremen, Germany
| | - Philipp F Hach
- Max Planck Institute for Marine Microbiology, Bremen, Germany
| | - Gaute Lavik
- Max Planck Institute for Marine Microbiology, Bremen, Germany
| | - Daan R Speth
- Max Planck Institute for Marine Microbiology, Bremen, Germany
- Division of Microbial Ecology, Center for Microbiology and Environmental Systems Science, University of Vienna, Vienna, Austria
| | - Carsten J Schubert
- Department of Surface Waters, Swiss Federal Institute of Aquatic Science and Technology (Eawag), Kastanienbaum, Switzerland
- Institute of Biogeochemistry and Pollutant Dynamics, ETH Zurich, Zurich, Switzerland
| | | | - Jana Milucka
- Max Planck Institute for Marine Microbiology, Bremen, Germany
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5
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Tschitschko B, Esti M, Philippi M, Kidane AT, Littmann S, Kitzinger K, Speth DR, Li S, Kraberg A, Tienken D, Marchant HK, Kartal B, Milucka J, Mohr W, Kuypers MMM. Rhizobia-diatom symbiosis fixes missing nitrogen in the ocean. Nature 2024; 630:899-904. [PMID: 38723661 PMCID: PMC11208148 DOI: 10.1038/s41586-024-07495-w] [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] [Received: 11/16/2023] [Accepted: 04/30/2024] [Indexed: 06/21/2024]
Abstract
Nitrogen (N2) fixation in oligotrophic surface waters is the main source of new nitrogen to the ocean1 and has a key role in fuelling the biological carbon pump2. Oceanic N2 fixation has been attributed almost exclusively to cyanobacteria, even though genes encoding nitrogenase, the enzyme that fixes N2 into ammonia, are widespread among marine bacteria and archaea3-5. Little is known about these non-cyanobacterial N2 fixers, and direct proof that they can fix nitrogen in the ocean has so far been lacking. Here we report the discovery of a non-cyanobacterial N2-fixing symbiont, 'Candidatus Tectiglobus diatomicola', which provides its diatom host with fixed nitrogen in return for photosynthetic carbon. The N2-fixing symbiont belongs to the order Rhizobiales and its association with a unicellular diatom expands the known hosts for this order beyond the well-known N2-fixing rhizobia-legume symbioses on land6. Our results show that the rhizobia-diatom symbioses can contribute as much fixed nitrogen as can cyanobacterial N2 fixers in the tropical North Atlantic, and that they might be responsible for N2 fixation in the vast regions of the ocean in which cyanobacteria are too rare to account for the measured rates.
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Affiliation(s)
- Bernhard Tschitschko
- Max Planck Institute for Marine Microbiology, Bremen, Germany
- Department of Microbiology, University of Innsbruck, Innsbruck, Austria
| | - Mertcan Esti
- Max Planck Institute for Marine Microbiology, Bremen, Germany
| | - Miriam Philippi
- Max Planck Institute for Marine Microbiology, Bremen, Germany
- Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
| | - Abiel T Kidane
- Max Planck Institute for Marine Microbiology, Bremen, Germany
| | - Sten Littmann
- Max Planck Institute for Marine Microbiology, Bremen, Germany
| | - Katharina Kitzinger
- Max Planck Institute for Marine Microbiology, Bremen, Germany
- Centre for Microbiology and Environmental Systems Science, Division of Microbial Ecology, University of Vienna, Vienna, Austria
| | - Daan R Speth
- Max Planck Institute for Marine Microbiology, Bremen, Germany
- Centre for Microbiology and Environmental Systems Science, Division of Microbial Ecology, University of Vienna, Vienna, Austria
| | - Shengjie Li
- Max Planck Institute for Marine Microbiology, Bremen, Germany
| | - Alexandra Kraberg
- Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
| | - Daniela Tienken
- Max Planck Institute for Marine Microbiology, Bremen, Germany
| | - Hannah K Marchant
- Max Planck Institute for Marine Microbiology, Bremen, Germany
- MARUM - Centre for Marine Environmental Sciences, University of Bremen, Bremen, Germany
| | - Boran Kartal
- Max Planck Institute for Marine Microbiology, Bremen, Germany
- School of Science, Constructor University, Bremen, Germany
| | - Jana Milucka
- Max Planck Institute for Marine Microbiology, Bremen, Germany
| | - Wiebke Mohr
- Max Planck Institute for Marine Microbiology, Bremen, Germany
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6
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Shen R, Borer B, Ciccarese D, Salek MM, Babbin AR. Microscale advection governs microbial growth and oxygen consumption in macroporous aggregates. mSphere 2024; 9:e0018524. [PMID: 38530018 PMCID: PMC11036798 DOI: 10.1128/msphere.00185-24] [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: 03/05/2024] [Accepted: 03/05/2024] [Indexed: 03/27/2024] Open
Abstract
Most microbial life on Earth is found in localized microenvironments that collectively exert a crucial role in maintaining ecosystem health and influencing global biogeochemical cycles. In many habitats such as biofilms in aquatic systems, bacterial flocs in activated sludge, periphyton mats, or particles sinking in the ocean, these microenvironments experience sporadic or continuous flow. Depending on their microscale structure, pores and channels through the microenvironments permit localized flow that shifts the relative importance of diffusive and advective mass transport. How this flow alters nutrient supply, facilitates waste removal, drives the emergence of different microbial niches, and impacts the overall function of the microenvironments remains unclear. Here, we quantify how pores through microenvironments that permit flow can elevate nutrient supply to the resident bacterial community using a microfluidic experimental system and gain further insights from coupled population-based and computational fluid dynamics simulations. We find that the microscale structure determines the relative contribution of advection vs diffusion, and even a modest flow through a pore in the range of 10 µm s-1 can increase the carrying capacity of a microenvironment by 10%. Recognizing the fundamental role that microbial hotspots play in the Earth system, developing frameworks that predict how their heterogeneous morphology and potential interstitial flows change microbial function and collectively alter global scale fluxes is critical.IMPORTANCEMicrobial life is a key driver of global biogeochemical cycles. Similar to the distribution of humans on Earth, they are often not homogeneously distributed in nature but occur in dense clusters that resemble microbial cities. Within and around these clusters, diffusion is often assumed as the sole mass-transfer process that dictates nutrient supply and waste removal. In many natural and engineered systems such as biofilms in aquatic environments, aggregates in bioremediation, or flocs in wastewater treatment plants, these clusters are exposed to flow that elevates mass transfer, a process that is often overlooked. In this study, we show that advective fluxes can increase the local growth of bacteria in a single microenvironment by up to 50% and shape their metabolism by disrupting localized anoxia or supplying nutrients at different rates. Collectively, advection-enhanced mass transport may thus regulate important biogeochemical transformations in both natural and engineered environments.
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Affiliation(s)
- Rachel Shen
- Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
| | - Benedict Borer
- Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
| | - Davide Ciccarese
- Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
| | - M. Mehdi Salek
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
| | - Andrew R. Babbin
- Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
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7
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Elbon CE, Stewart FJ, Glass JB. Novel Alphaproteobacteria transcribe genes for nitric oxide transformation at high levels in a marine oxygen-deficient zone. Appl Environ Microbiol 2024; 90:e0209923. [PMID: 38445905 PMCID: PMC11022542 DOI: 10.1128/aem.02099-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2023] [Accepted: 02/09/2024] [Indexed: 03/07/2024] Open
Abstract
Marine oxygen-deficient zones (ODZs) are portions of the ocean where intense nitrogen loss occurs primarily via denitrification and anammox. Despite many decades of study, the identity of the microbes that catalyze nitrogen loss in ODZs is still being elucidated. Intriguingly, high transcription of genes in the same family as the nitric oxide dismutase (nod) gene from Methylomirabilota has been reported in the anoxic core of ODZs. Here, we show that the most abundantly transcribed nod genes in the Eastern Tropical North Pacific ODZ belong to a new order (UBA11136) of Alphaproteobacteria, rather than Methylomirabilota as previously assumed. Gammaproteobacteria and Planctomycetia also transcribe nod, but at lower relative abundance than UBA11136 in the upper ODZ. The nod-transcribing Alphaproteobacteria likely use formaldehyde and formate as a source of electrons for aerobic respiration, with additional electrons possibly from sulfide oxidation. They also transcribe multiheme cytochrome (here named ptd) genes for a putative porin-cytochrome protein complex of unknown function, potentially involved in extracellular electron transfer. Molecular oxygen for aerobic respiration may originate from nitric oxide dismutation via cryptic oxygen cycling. Our results implicate Alphaproteobacteria order UBA11136 as a significant player in marine nitrogen loss and highlight their potential in one-carbon, nitrogen, and sulfur metabolism in ODZs.IMPORTANCEIn marine oxygen-deficient zones (ODZs), microbes transform bioavailable nitrogen to gaseous nitrogen, with nitric oxide as a key intermediate. The Eastern Tropical North Pacific contains the world's largest ODZ, but the identity of the microbes transforming nitric oxide remains unknown. Here, we show that highly transcribed nitric oxide dismutase (nod) genes belong to Alphaproteobacteria of the novel order UBA11136, which lacks cultivated isolates. These Alphaproteobacteria show evidence for aerobic respiration, using oxygen potentially sourced from nitric oxide dismutase, and possess a novel porin-cytochrome protein complex with unknown function. Gammaproteobacteria and Planctomycetia transcribe nod at lower levels. Our results pinpoint the microbes mediating a key step in marine nitrogen loss and reveal an unexpected predicted metabolism for marine Alphaproteobacteria.
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Affiliation(s)
- Claire E. Elbon
- School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - Frank J. Stewart
- Department of Microbiology & Cell Biology, Montana State University, Bozeman, Montana, USA
| | - Jennifer B. Glass
- School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia, USA
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8
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Martins MC, Alves CM, Teixeira M, Folgosa F. The flavodiiron protein from Syntrophomonas wolfei has five domains and acts both as an NADH:O 2 or an NADH:H 2 O 2 oxidoreductase. FEBS J 2024; 291:1275-1294. [PMID: 38129989 DOI: 10.1111/febs.17040] [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: 07/06/2023] [Revised: 11/10/2023] [Accepted: 12/20/2023] [Indexed: 12/23/2023]
Abstract
Flavodiiron proteins (FDPs) are a family of enzymes with a significant role in O2 /H2 O2 and/or NO detoxification through the reduction of these species to H2 O or N2 O, respectively. All FDPs contain a minimal catalytic unit of two identical subunits, each one having a metallo-β-lactamase-like domain harboring the catalytic diiron site, and a flavodoxin-like domain. However, more complex and diverse arrangements in terms of domains are found in this family, of which the class H enzymes are among the most complex. One of such FDPs is encoded in the genome of the anaerobic bacterium Syntrophomonas wolfei subsp. wolfei str. Goettingen G311. Besides the core domains, this protein is predicted to have three additional ones after the flavodoxin core domain: two short-chain rubredoxins and a NAD(P)H:rubredoxin oxidoreductase-like domain. This enzyme, FDP_H, was produced and characterized and the presence of the predicted cofactors was investigated by a set of biochemical and spectroscopic methodologies. Syntrophomonas wolfei FDP_H exhibited a remarkable O2 reduction activity with a kcat = 52.0 ± 1.2 s-1 and a negligible NO reduction activity (~ 100 times lower than with O2 ), with NADH as an electron donor, that is, it is an oxygen-selective FDP. In addition, this enzyme showed the highest turnover value for H2 O2 reduction (kcat = 19.1 ± 2.2 s-1 ) ever observed among FDPs. Kinetic studies of site-directed mutants of iron-binding cysteines at the two rubredoxin domains demonstrated the essential role of these centers since their absence leads to a significant decrease or even abolishment of O2 and H2 O2 reduction activities.
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Affiliation(s)
- Maria C Martins
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Oeiras, Portugal
| | - Catarina M Alves
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Oeiras, Portugal
| | - Miguel Teixeira
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Oeiras, Portugal
| | - Filipe Folgosa
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Oeiras, Portugal
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9
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Mills DB, Simister RL, Sehein TR, Hallam SJ, Sperling EA, Crowe SA. Constraining the oxygen requirements for modern microbial eukaryote diversity. Proc Natl Acad Sci U S A 2024; 121:e2303754120. [PMID: 38165897 PMCID: PMC10786294 DOI: 10.1073/pnas.2303754120] [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: 03/06/2023] [Accepted: 11/07/2023] [Indexed: 01/04/2024] Open
Abstract
Eukaryotes originated prior to the establishment of modern marine oxygen (O2) levels. According to the body fossil and lipid biomarker records, modern (crown) microbial eukaryote lineages began diversifying in the ocean no later than ~800 Ma. While it has long been predicted that increasing atmospheric O2 levels facilitated the early diversification of microbial eukaryotes, the O2 levels needed to permit this diversification remain unconstrained. Using time-resolved geochemical parameter and gene sequence information from a model marine oxygen minimum zone spanning a range of dissolved O2 levels and redox states, we show that microbial eukaryote taxonomic richness and phylogenetic diversity remain the same until O2 declines to around 2 to 3% of present atmospheric levels, below which these diversity metrics become significantly reduced. Our observations suggest that increasing O2 would have only directly promoted early crown-eukaryote diversity if atmospheric O2 was below 2 to 3% of modern levels when crown-eukaryotes originated and then later met or surpassed this range as crown-eukaryotes diversified. If atmospheric O2 was already consistently at or above 2 to 3% of modern levels by the time that crown-eukaryotes originated, then the subsequent diversification of modern microbial eukaryotes was not directly driven by atmospheric oxygenation.
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Affiliation(s)
- Daniel B. Mills
- Department of Earth and Environmental Sciences, Paleontology and Geobiology, Ludwig-Maximilians-Universität München, 80333Munich, Germany
- Department of Earth and Planetary Sciences, Stanford University, Stanford, CA94305
- The Penn State Extraterrestrial Intelligence Center, The Pennsylvania State University, University Park, PA16802
| | - Rachel L. Simister
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, BCV6T 1Z4, Canada
| | - Taylor R. Sehein
- Department of Biological Sciences, Smith College, Northampton, MA01063
| | - Steven J. Hallam
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, BCV6T 1Z4, Canada
- Genome Science and Technology Program, University of British Columbia, Vancouver, BCV6T 1Z4, Canada
- Graduate Program in Bioinformatics, University of British Columbia, Vancouver, BCV6T 1Z4, Canada
- Life Sciences Institute, University of British Columbia, Vancouver, BCV6T 1Z3, Canada
- Bradshaw Research Initiative for Minerals and Mining, University of British Columbia, Vancouver, BCV6T 1Z4, Canada
- Ecosystem Services, Commercialization Platforms and Entrepreneurship (ECOSCOPE) Training Program, University of British Columbia, Vancouver, BCV6T 1Z3, Canada
| | - Erik A. Sperling
- Department of Earth and Planetary Sciences, Stanford University, Stanford, CA94305
| | - Sean A. Crowe
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, BCV6T 1Z4, Canada
- Department of Earth, Ocean, and Atmospheric Sciences, University of British Columbia, Vancouver, BCV6T 1Z4, Canada
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10
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Bai B, Zhang L, Dong H, Huang Y. Coupled Fe(III) reduction and phenanthrene degradation by marine-derived Kocuria oceani FXJ8.057 under aerobic condition. JOURNAL OF HAZARDOUS MATERIALS 2023; 459:132237. [PMID: 37595472 DOI: 10.1016/j.jhazmat.2023.132237] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/02/2023] [Revised: 06/29/2023] [Accepted: 08/04/2023] [Indexed: 08/20/2023]
Abstract
Diverse aerobic actinobacteria possess the capacity to degrade polycyclic aromatic hydrocarbons (PAHs) and have recently been shown to reduce Fe(III). However, the coupling of the two processes under oxic conditions remains unclear. Here, the co-metabolism of phenanthrene (PHE) and Fe(III) by marine-derived Kocuria oceani FXJ8.057 was realized under aerobic condition. In the presence of both PHE and Fe(III), the rates of PHE degradation (83.91 %) and Fe(III) reduction (50.00 %) were synchronously enhanced, compared to those with PHE (67.34 %) or Fe(III) (38.00 %) alone. Transcriptome analysis detected upregulation of PHE biodegradation and riboflavin biosynthesis in the strain cultured with both PHE and Fe(III) compared to that with PHE alone. Metabolite analysis indicated that, with the addition of Fe(III), the strain could efficiently degrade PHE via three pathways. Moreover, the strain secreted riboflavin, which acted as a shuttle to promote electron transfer from PHE to Fe(III). It also secreted organic acids that could delay Fe(II) reoxidation. Finally, H2O2 secreted by the strain caused extracellular Fenton reaction to generate •OH, which also played a minor role in the PHE degradation. These findings provide the first example of an aerobic bacterium that couples PAH degradation to Fe(III) reduction and extend our understanding of Fe(III)-reducing microorganisms.
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Affiliation(s)
- Bingbing Bai
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China; College of Life Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Limin Zhang
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China.
| | - Hailiang Dong
- Center for Geomicrobiology and Biogeochemistry Research, State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Beijing 100083, China
| | - Ying Huang
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China; College of Life Sciences, University of Chinese Academy of Sciences, Beijing 100049, China.
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11
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Yang Y, Rivera Pérez CA, Richter-Heitmann T, Nimzyk R, Friedrich MW, Reich M. Effects of oxygen availability on mycobenthic communities of marine coastal sediments. Sci Rep 2023; 13:15218. [PMID: 37709848 PMCID: PMC10502103 DOI: 10.1038/s41598-023-42329-1] [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: 04/17/2023] [Accepted: 09/08/2023] [Indexed: 09/16/2023] Open
Abstract
In coastal marine sediments, oxygen availability varies greatly, and anoxic conditions can develop quickly over low spatial resolution. Although benthic fungi are important players in the marine carbon cycle, little is known about their adaptation to fluctuating availability of oxygen as terminal electron acceptor. Here, we study which part of a mycobenthic community from oxic coastal sediments can thrive under temporarily anoxic conditions. We test whether phylogeny or certain fungal traits promote plasticity in respect to changes in oxygen availability. Therefore, we incubated mycobenthos under oxic and anoxic conditions, performed ITS2 Illumina tag-sequencing and an additional meta-analysis on a literature survey. Half of all OTUs showed a plasticity towards changing oxygen availability and exhibited different strategies towards anoxic conditions, with rapid response within hours or a delayed one after several days. The strategy of dimorphism and facultative yeasts were significantly linked to OTU occurrence in anoxic conditions, while phylogeny and other traits had less effect. Our results suggest that different fungal niches are formed over the duration of prolonged anoxic conditions. The taxon-specific proliferation seems to be regulated by the fine-tuning of various traits and factors. It is essential to take these results into account when conducting conceptual work on the functionality of the marine benthos.
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Affiliation(s)
- Yanyan Yang
- Molecular Ecology Group, Faculty of Biology and Chemistry, University of Bremen, Bremen, Germany
| | - Carmen Alicia Rivera Pérez
- Molecular Ecology Group, Faculty of Biology and Chemistry, University of Bremen, Bremen, Germany
- Biodiversity and Evolution of Plants, Institute of Biology and Environmental Sciences, Carl von Ossietzky University of Oldenburg, Oldenburg, Germany
| | - Tim Richter-Heitmann
- Microbial Ecophysiology Group, Faculty of Biology and Chemistry, University of Bremen, Bremen, Germany
| | - Rolf Nimzyk
- Microbial Ecophysiology Group, Faculty of Biology and Chemistry, University of Bremen, Bremen, Germany
| | - Michael W Friedrich
- Microbial Ecophysiology Group, Faculty of Biology and Chemistry, University of Bremen, Bremen, Germany
- MARUM, Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany
| | - Marlis Reich
- Molecular Ecology Group, Faculty of Biology and Chemistry, University of Bremen, Bremen, Germany.
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12
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Magnuson E, Altshuler I, Freyria NJ, Leveille RJ, Whyte LG. Sulfur-cycling chemolithoautotrophic microbial community dominates a cold, anoxic, hypersaline Arctic spring. MICROBIOME 2023; 11:203. [PMID: 37697305 PMCID: PMC10494364 DOI: 10.1186/s40168-023-01628-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/12/2023] [Accepted: 07/19/2023] [Indexed: 09/13/2023]
Abstract
BACKGROUND Gypsum Hill Spring, located in Nunavut in the Canadian High Arctic, is a rare example of a cold saline spring arising through thick permafrost. It perennially discharges cold (~ 7 °C), hypersaline (7-8% salinity), anoxic (~ 0.04 ppm O2), and highly reducing (~ - 430 mV) brines rich in sulfate (2.2 g.L-1) and sulfide (9.5 ppm), making Gypsum Hill an analog to putative sulfate-rich briny habitats on extraterrestrial bodies such as Mars. RESULTS Genome-resolved metagenomics and metatranscriptomics were utilized to describe an active microbial community containing novel metagenome-assembled genomes and dominated by sulfur-cycling Desulfobacterota and Gammaproteobacteria. Sulfate reduction was dominated by hydrogen-oxidizing chemolithoautotrophic Desulfovibrionaceae sp. and was identified in phyla not typically associated with sulfate reduction in novel lineages of Spirochaetota and Bacteroidota. Highly abundant and active sulfur-reducing Desulfuromusa sp. highly transcribed non-coding RNAs associated with transcriptional regulation, showing potential evidence of putative metabolic flexibility in response to substrate availability. Despite low oxygen availability, sulfide oxidation was primarily attributed to aerobic chemolithoautotrophic Halothiobacillaceae. Low abundance and transcription of photoautotrophs indicated sulfur-based chemolithoautotrophy drives primary productivity even during periods of constant illumination. CONCLUSIONS We identified a rare surficial chemolithoautotrophic, sulfur-cycling microbial community active in a unique anoxic, cold, hypersaline Arctic spring. We detected Mars-relevant metabolisms including hydrogenotrophic sulfate reduction, sulfur reduction, and sulfide oxidation, which indicate the potential for microbial life in analogous S-rich brines on past and present Mars. Video Abstract.
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Affiliation(s)
- Elisse Magnuson
- Natural Resource Sciences, McGill University, Ste-Anne-de-Bellevue, QC Canada
| | - Ianina Altshuler
- MACE Laboratory, ALPOLE, School of Architecture, Civil and Environmental Engineering (ENAC), Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
| | - Nastasia J. Freyria
- Natural Resource Sciences, McGill University, Ste-Anne-de-Bellevue, QC Canada
| | - Richard J. Leveille
- Department of Earth and Planetary Sciences, McGill University, Montreal, QC Canada
- Geosciences Department, John Abbott College, Ste-Anne-de-Bellevue, QC Canada
| | - Lyle G. Whyte
- Natural Resource Sciences, McGill University, Ste-Anne-de-Bellevue, QC Canada
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13
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Ciccarese D, Tantawi O, Zhang IH, Plata D, Babbin AR. Microscale dynamics promote segregated denitrification in diatom aggregates sinking slowly in bulk oxygenated seawater. COMMUNICATIONS EARTH & ENVIRONMENT 2023; 4:275. [PMID: 38665198 PMCID: PMC11041763 DOI: 10.1038/s43247-023-00935-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/23/2022] [Accepted: 07/18/2023] [Indexed: 04/28/2024]
Abstract
Sinking marine particles drive the biological pump that naturally sequesters carbon from the atmosphere. Despite their small size, the compartmentalized nature of particles promotes intense localized metabolic activity by their bacterial colonizers. Yet the mechanisms promoting the onset of denitrification, a metabolism that arises once oxygen is limiting, remain to be established. Here we show experimentally that slow sinking aggregates composed of marine diatoms-important primary producers for global carbon export-support active denitrification even among bulk oxygenated water typically thought to exclude anaerobic metabolisms. Denitrification occurs at anoxic microsites distributed throughout a particle and within microns of a particle's boundary, and fluorescence-reporting bacteria show nitrite can be released into the water column due to segregated dissimilatory reduction of nitrate and nitrite. Examining intact and broken diatoms as organic sources, we show slowly leaking cells promote more bacterial growth, allow particles to have lower oxygen, and generally support greater denitrification.
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Affiliation(s)
- Davide Ciccarese
- Department of Earth, Atmospheric & Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA USA
| | - Omar Tantawi
- Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, MA USA
| | - Irene H. Zhang
- Department of Earth, Atmospheric & Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA USA
- Program in Microbiology, Massachusetts Institute of Technology, Cambridge, MA USA
| | - Desiree Plata
- Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, MA USA
| | - Andrew R. Babbin
- Department of Earth, Atmospheric & Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA USA
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14
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Kasahara K, Leygeber M, Seiffarth J, Ruzaeva K, Drepper T, Nöh K, Kohlheyer D. Enabling oxygen-controlled microfluidic cultures for spatiotemporal microbial single-cell analysis. Front Microbiol 2023; 14:1198170. [PMID: 37408642 PMCID: PMC10318409 DOI: 10.3389/fmicb.2023.1198170] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2023] [Accepted: 05/30/2023] [Indexed: 07/07/2023] Open
Abstract
Microfluidic cultivation devices that facilitate O2 control enable unique studies of the complex interplay between environmental O2 availability and microbial physiology at the single-cell level. Therefore, microbial single-cell analysis based on time-lapse microscopy is typically used to resolve microbial behavior at the single-cell level with spatiotemporal resolution. Time-lapse imaging then provides large image-data stacks that can be efficiently analyzed by deep learning analysis techniques, providing new insights into microbiology. This knowledge gain justifies the additional and often laborious microfluidic experiments. Obviously, the integration of on-chip O2 measurement and control during the already complex microfluidic cultivation, and the development of image analysis tools, can be a challenging endeavor. A comprehensive experimental approach to allow spatiotemporal single-cell analysis of living microorganisms under controlled O2 availability is presented here. To this end, a gas-permeable polydimethylsiloxane microfluidic cultivation chip and a low-cost 3D-printed mini-incubator were successfully used to control O2 availability inside microfluidic growth chambers during time-lapse microscopy. Dissolved O2 was monitored by imaging the fluorescence lifetime of the O2-sensitive dye RTDP using FLIM microscopy. The acquired image-data stacks from biological experiments containing phase contrast and fluorescence intensity data were analyzed using in-house developed and open-source image-analysis tools. The resulting oxygen concentration could be dynamically controlled between 0% and 100%. The system was experimentally tested by culturing and analyzing an E. coli strain expressing green fluorescent protein as an indirect intracellular oxygen indicator. The presented system allows for innovative microbiological research on microorganisms and microbial ecology with single-cell resolution.
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Affiliation(s)
- Keitaro Kasahara
- IBG-1: Biotechnology, Institute of Bio- and Geosciences, Forschungszentrum Jülich GmbH, Jülich, Germany
| | - Markus Leygeber
- IBG-1: Biotechnology, Institute of Bio- and Geosciences, Forschungszentrum Jülich GmbH, Jülich, Germany
| | - Johannes Seiffarth
- IBG-1: Biotechnology, Institute of Bio- and Geosciences, Forschungszentrum Jülich GmbH, Jülich, Germany
- Computational Systems Biotechnology (AVT.CSB), RWTH Aachen University, Aachen, Germany
| | - Karina Ruzaeva
- IBG-1: Biotechnology, Institute of Bio- and Geosciences, Forschungszentrum Jülich GmbH, Jülich, Germany
- Aachen Institute for Advanced Study in Computational Engineering Science (AICES), RWTH Aachen University, Aachen, Germany
| | - Thomas Drepper
- Institute of Molecular Enzyme Technology, Heinrich Heine University Düsseldorf, Forschungszentrum Jülich GmbH, Jülich, Germany
| | - Katharina Nöh
- IBG-1: Biotechnology, Institute of Bio- and Geosciences, Forschungszentrum Jülich GmbH, Jülich, Germany
| | - Dietrich Kohlheyer
- IBG-1: Biotechnology, Institute of Bio- and Geosciences, Forschungszentrum Jülich GmbH, Jülich, Germany
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15
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Butler NL, Ito T, Foreman S, Morgan JE, Zagorevsky D, Malamy MH, Comstock LE, Barquera B. Bacteroides fragilis Maintains Concurrent Capability for Anaerobic and Nanaerobic Respiration. J Bacteriol 2023; 205:e0038922. [PMID: 36475831 PMCID: PMC9879120 DOI: 10.1128/jb.00389-22] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2022] [Accepted: 11/02/2022] [Indexed: 12/13/2022] Open
Abstract
Bacteroides species can use fumarate and oxygen as terminal electron acceptors during cellular respiration. In the human gut, oxygen diffuses from intestinal epithelial cells supplying "nanaerobic" oxygen levels. Many components of the anaerobic respiratory pathway have been determined, but such analyses have not been performed for nanaerobic respiration. Here, we present genetic, biochemical, enzymatic, and mass spectrometry analyses to elucidate the nanaerobic respiratory pathway in Bacteroides fragilis. Under anaerobic conditions, the transfer of electrons from NADH to the quinone pool has been shown to be contributed by two enzymes, NQR and NDH2. We find that the activity contributed by each under nanaerobic conditions is 77 and 23%, respectively, similar to the activity levels under anaerobic conditions. Using mass spectrometry, we show that the quinone pool also does not differ under these two conditions and consists of a mixture of menaquinone-8 to menaquinone-11, with menaquinone-10 predominant under both conditions. Analysis of fumarate reductase showed that it is synthesized and active under anaerobic and nanaerobic conditions. Previous RNA sequencing data and new transcription reporter assays show that expression of the cytochrome bd oxidase gene does not change under these conditions. Under nanaerobic conditions, we find both increased CydA protein and increased cytochrome bd activity. Reduced-minus-oxidized spectra of membranes showed the presence of heme d when the bacteria were grown in the presence of protoporphyrin IX and iron under both anaerobic and nanaerobic conditions, suggesting that the active oxidase can be assembled with or without oxygen. IMPORTANCE By performing a comprehensive analysis of nanaerobic respiration in Bacteroides fragilis, we show that this organism maintains capabilities for anaerobic respiration on fumarate and nanaerobic respiration on oxygen simultaneously. The contribution of the two NADH:quinone oxidoreductases and the composition of the quinone pool are the same under both conditions. Fumarate reductase and cytochrome bd are both present, and which of these terminal enzymes is active in electron transfer depends on the availability of the final electron acceptor: fumarate or oxygen. The synthesis of cytochrome bd and fumarate reductase under both conditions serves as an adaptation to an environment with low oxygen concentrations so that the bacteria can maximize energy conservation during fluctuating environmental conditions or occupation of different spatial niches.
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Affiliation(s)
- Nicole L. Butler
- Department of Chemistry and Chemical Biology, Rensselaer Polytechnic Institute, Troy, New York, USA
| | - Takeshi Ito
- Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, New York, USA
| | - Sara Foreman
- Department of Chemistry and Chemical Biology, Rensselaer Polytechnic Institute, Troy, New York, USA
| | - Joel E. Morgan
- Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, New York, USA
| | - Dmitry Zagorevsky
- Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, New York, USA
| | - Michael H. Malamy
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts, USA
| | - Laurie E. Comstock
- Duchossois Family Institute and Department of Microbiology, University of Chicago, Chicago, Illinois, USA
| | - Blanca Barquera
- Department of Chemistry and Chemical Biology, Rensselaer Polytechnic Institute, Troy, New York, USA
- Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, New York, USA
- Department of Biological Sciences, Rensselaer Polytechnic Institute, Troy, New York, USA
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16
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Dunn AK. Alternative oxidase in bacteria. BIOCHIMICA ET BIOPHYSICA ACTA. BIOENERGETICS 2023; 1864:148929. [PMID: 36265564 DOI: 10.1016/j.bbabio.2022.148929] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/04/2022] [Revised: 09/20/2022] [Accepted: 10/12/2022] [Indexed: 11/06/2022]
Abstract
While alternative oxidase (AOX) was discovered in bacteria in 2003, the expression, function, and evolutionary history of this protein in these important organisms is largely unexplored. To date, expression and functional analysis is limited to studies in the Proteobacteria Novosphingobium aromaticivorans and Vibrio fischeri, where AOX likely plays roles in maintenance of cellular energy homeostasis and supporting responses to cellular stress. This review describes the history of the study of AOX in bacteria, details current knowledge of the predicted biochemical and structural characteristics, distribution, and function of bacterial AOX, and highlights interesting areas for the future study of AOX in bacteria.
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Affiliation(s)
- Anne K Dunn
- Department of Microbiology and Plant Biology, University of Oklahoma, 770 Van Vleet Oval, Norman, OK 73019, USA.
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17
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Bauwe H. Photorespiration - Rubisco's repair crew. JOURNAL OF PLANT PHYSIOLOGY 2023; 280:153899. [PMID: 36566670 DOI: 10.1016/j.jplph.2022.153899] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2022] [Revised: 12/11/2022] [Accepted: 12/11/2022] [Indexed: 06/17/2023]
Abstract
The photorespiratory repair pathway (photorespiration in short) was set up from ancient metabolic modules about three billion years ago in cyanobacteria, the later ancestors of chloroplasts. These prokaryotes developed the capacity for oxygenic photosynthesis, i.e. the use of water as a source of electrons and protons (with O2 as a by-product) for the sunlight-driven synthesis of ATP and NADPH for CO2 fixation in the Calvin cycle. However, the CO2-binding enzyme, ribulose 1,5-bisphosphate carboxylase (known under the acronym Rubisco), is not absolutely selective for CO2 and can also use O2 in a side reaction. It then produces 2-phosphoglycolate (2PG), the accumulation of which would inhibit and potentially stop the Calvin cycle and subsequently photosynthetic electron transport. Photorespiration removes the 2-PG and in this way prevents oxygenic photosynthesis from poisoning itself. In plants, the core of photorespiration consists of ten enzymes distributed over three different types of organelles, requiring interorganellar transport and interaction with several auxiliary enzymes. It goes together with the release and to some extent loss of freshly fixed CO2. This disadvantageous feature can be suppressed by CO2-concentrating mechanisms, such as those that evolved in C4 plants thirty million years ago, which enhance CO2 fixation and reduce 2PG synthesis. Photorespiration itself provided a pioneer variant of such mechanisms in the predecessors of C4 plants, C3-C4 intermediate plants. This article is a review and update particularly on the enzyme components of plant photorespiration and their catalytic mechanisms, on the interaction of photorespiration with other metabolism and on its impact on the evolution of photosynthesis. This focus was chosen because a better knowledge of the enzymes involved and how they are embedded in overall plant metabolism can facilitate the targeted use of the now highly advanced methods of metabolic network modelling and flux analysis. Understanding photorespiration more than before as a process that enables, rather than reduces, plant photosynthesis, will help develop rational strategies for crop improvement.
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Affiliation(s)
- Hermann Bauwe
- University of Rostock, Plant Physiology, Albert-Einstein-Straße 3, D-18051, Rostock, Germany.
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18
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Flamholz AI, Saccomano S, Cash K, Newman DK. Optical O 2 Sensors Also Respond to Redox Active Molecules Commonly Secreted by Bacteria. mBio 2022; 13:e0207622. [PMID: 36314810 PMCID: PMC9765510 DOI: 10.1128/mbio.02076-22] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2022] [Accepted: 10/07/2022] [Indexed: 11/06/2022] Open
Abstract
From a metabolic perspective, molecular oxygen (O2) is arguably the most significant constituent of Earth's atmosphere. Nearly every facet of microbial physiology is sensitive to the presence and concentration of O2, which is the most favorable terminal electron acceptor used by organisms and also a dangerously reactive oxidant. As O2 has such sweeping implications for physiology, researchers have developed diverse approaches to measure O2 concentrations in natural and laboratory settings. Recent improvements to phosphorescent O2 sensors piqued our interest due to the promise of optical measurement of spatiotemporal O2 dynamics. However, we found that our preferred bacterial model, Pseudomonas aeruginosa PA14, secretes more than one molecule that quenches such sensors, complicating O2 measurements in PA14 cultures and biofilms. Assaying supernatants from cultures of 9 bacterial species demonstrated that this phenotype is common: all supernatants quenched a soluble O2 probe substantially. Phosphorescent O2 probes are often embedded in solid support for protection, but an embedded probe called O2NS was quenched by most supernatants as well. Measurements using pure compounds indicated that quenching is due to interactions with redox-active small molecules, including phenazines and flavins. Uncharged and weakly polar molecules like pyocyanin were especially potent quenchers of O2NS. These findings underscore that optical O2 measurements made in the presence of bacteria should be carefully controlled to ensure that O2, and not bacterial secretions, is measured, and motivate the design of custom O2 probes for specific organisms to circumvent sensitivity to redox-active metabolites. IMPORTANCE When they are closely packed, as in biofilms, colonies, and soils, microbes can consume O2 faster than it diffuses. As such, O2 concentrations in natural environments can vary greatly over time and space, even on the micrometer scale. Wetting soil, for example, slows O2 diffusion higher in the soil column, which, in concert with microbial respiration, greatly diminishes [O2] at depth. Given that variation in [O2] has outsized implications for microbial physiology, there is great interest in measuring the dynamics of [O2] in microbial cultures and biofilms. We demonstrate that certain classes of bacterial metabolites frustrate optical measurement of [O2] with phosphorescent sensors, but also that some species (e.g., E. coli) do not produce problematic secretions under the conditions tested. Our work therefore offers a strategy for identifying organisms and culture conditions in which optical quantification of spatiotemporal [O2] dynamics with current sensors is feasible.
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Affiliation(s)
- Avi I. Flamholz
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, California, USA
- Resnick Sustainability Institute, California Institute of Technology, Pasadena, California, USA
| | - Samuel Saccomano
- Chemical and Biological Engineering, Colorado School of Mines, Golden, Colorado, USA
| | - Kevin Cash
- Chemical and Biological Engineering, Colorado School of Mines, Golden, Colorado, USA
- Quantitative Biosciences and Engineering, Colorado School of Mines, Golden, Colorado, USA
| | - Dianne K. Newman
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, California, USA
- Resnick Sustainability Institute, California Institute of Technology, Pasadena, California, USA
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA
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19
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Ceriotti G, Borisov SM, Berg JS, de Anna P. Morphology and Size of Bacterial Colonies Control Anoxic Microenvironment Formation in Porous Media. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2022; 56:17471-17480. [PMID: 36414252 DOI: 10.1021/acs.est.2c05842] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Bacterial metabolisms using electron acceptors other than oxygen (e.g., methanogenesis and fermentation) largely contribute to element cycling and natural contaminant attenuation/mobilization, even in well-oxygenated porous environments, such as shallow aquifers. This paradox is commonly explained by the occurrence of small-scale anoxic microenvironments generated by the coupling of bacterial respiration and dissolved oxygen (O2) transport by pore water. Such microenvironments allow facultative anaerobic bacteria to proliferate in oxic environments. Microenvironment dynamics are still poorly understood due to the challenge of directly observing biomass and O2 distributions at the microscale within an opaque sediment matrix. To overcome these limitations, we integrated a microfluidic device with transparent O2 planar optical sensors to measure the temporal behavior of dissolved O2 concentrations and biomass distributions with time-lapse videomicroscopy. Our results reveal that bacterial colony morphology, which is highly variable in flowing porous systems, controls the formation of anoxic microenvironments. We rationalize our observations through a colony-scale Damköhler number comparing dissolved O2 diffusion and a bacterial O2 uptake rate. Our Damköhler number enables us to predict the pore space fraction occupied by anoxic microenvironments in our system for a given bacterial organization.
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Affiliation(s)
- Giulia Ceriotti
- Institute of Earth Surface Dynamics, University of Lausanne, Lausanne1015, Switzerland
| | - Sergey M Borisov
- Institute of Analytical Chemistry and Food Chemistry, Graz University of Technology, Graz8010, Austria
| | - Jasmine S Berg
- Institute of Earth Surface Dynamics, University of Lausanne, Lausanne1015, Switzerland
| | - Pietro de Anna
- Institute of Earth Sciences, University of Lausanne, Lausanne1015, Switzerland
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20
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Canfield DE, Kraft B. The 'oxygen' in oxygen minimum zones. Environ Microbiol 2022; 24:5332-5344. [PMID: 36054074 PMCID: PMC9828761 DOI: 10.1111/1462-2920.16192] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2022] [Accepted: 08/31/2022] [Indexed: 01/12/2023]
Abstract
Aerobic processes require oxygen, and anaerobic processes are typically hindered by it. In many places in the global ocean, oxygen is completely removed at mid-water depths forming anoxic oxygen minimum zones (A-OMZs). Within the oxygen gradients linking oxygenated waters with A-OMZs, there is a transition from aerobic to anaerobic microbial processes. This transition is not sharp and there is an overlap between processes using oxygen and those using other electron acceptors. This review will focus on the oxygen control of aerobic and anaerobic metabolisms and will explore how this overlap impacts both the carbon and nitrogen cycles in A-OMZ environments. We will discuss new findings on non-phototrophic microbial processes that produce oxygen, and we focus on how oxygen impacts the loss of fixed nitrogen (as N2 ) from A-OMZ waters. There are both physiological and environmental controls on the activities of microbial processes responsible for N2 loss, and the environmental controls are active at extremely low levels of oxygen. Understanding how these controls function will be critical to understanding and predicting how fixed-nitrogen loss in the oceans will respond to future global warming.
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Affiliation(s)
- Don E. Canfield
- Department of Biology and NordceeUniversity of Southern Denmark, Campusvej 55OdenseDenmark,Danish Institute for Advanced Studies (DIAS)Denmark,PetrochinaBeijingChina
| | - Beate Kraft
- Department of Biology and NordceeUniversity of Southern Denmark, Campusvej 55OdenseDenmark
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21
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Magnuson E, Altshuler I, Fernández-Martínez MÁ, Chen YJ, Maggiori C, Goordial J, Whyte LG. Active lithoautotrophic and methane-oxidizing microbial community in an anoxic, sub-zero, and hypersaline High Arctic spring. THE ISME JOURNAL 2022; 16:1798-1808. [PMID: 35396347 PMCID: PMC9213412 DOI: 10.1038/s41396-022-01233-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2021] [Revised: 03/21/2022] [Accepted: 03/29/2022] [Indexed: 05/01/2023]
Abstract
Lost Hammer Spring, located in the High Arctic of Nunavut, Canada, is one of the coldest and saltiest terrestrial springs discovered to date. It perennially discharges anoxic (<1 ppm dissolved oxygen), sub-zero (~-5 °C), and hypersaline (~24% salinity) brines from the subsurface through up to 600 m of permafrost. The sediment is sulfate-rich (1 M) and continually emits gases composed primarily of methane (~50%), making Lost Hammer the coldest known terrestrial methane seep and an analog to extraterrestrial habits on Mars, Europa, and Enceladus. A multi-omics approach utilizing metagenome, metatranscriptome, and single-amplified genome sequencing revealed a rare surface terrestrial habitat supporting a predominantly lithoautotrophic active microbial community driven in part by sulfide-oxidizing Gammaproteobacteria scavenging trace oxygen. Genomes from active anaerobic methane-oxidizing archaea (ANME-1) showed evidence of putative metabolic flexibility and hypersaline and cold adaptations. Evidence of anaerobic heterotrophic and fermentative lifestyles were found in candidate phyla DPANN archaea and CG03 bacteria genomes. Our results demonstrate Mars-relevant metabolisms including sulfide oxidation, sulfate reduction, anaerobic oxidation of methane, and oxidation of trace gases (H2, CO2) detected under anoxic, hypersaline, and sub-zero ambient conditions, providing evidence that similar extant microbial life could potentially survive in similar habitats on Mars.
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Affiliation(s)
- Elisse Magnuson
- Natural Resource Sciences, McGill University, Ste-Anne-de-Bellevue, QC, Canada
| | - Ianina Altshuler
- School of Architecture, Civil and Environmental Engineering, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
| | | | - Ya-Jou Chen
- Natural Resource Sciences, McGill University, Ste-Anne-de-Bellevue, QC, Canada
| | - Catherine Maggiori
- Natural Resource Sciences, McGill University, Ste-Anne-de-Bellevue, QC, Canada
| | | | - Lyle G Whyte
- Natural Resource Sciences, McGill University, Ste-Anne-de-Bellevue, QC, Canada.
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22
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Eukaryogenesis and oxygen in Earth history. Nat Ecol Evol 2022; 6:520-532. [PMID: 35449457 DOI: 10.1038/s41559-022-01733-y] [Citation(s) in RCA: 34] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2021] [Accepted: 03/15/2022] [Indexed: 02/07/2023]
Abstract
The endosymbiotic origin of mitochondria during eukaryogenesis has long been viewed as an adaptive response to the oxygenation of Earth's surface environment, presuming a fundamentally aerobic lifestyle for the free-living bacterial ancestors of mitochondria. This oxygen-centric view has been robustly challenged by recent advances in the Earth and life sciences. While the permanent oxygenation of the atmosphere above trace concentrations is now thought to have occurred 2.2 billion years ago, large parts of the deep ocean remained anoxic until less than 0.5 billion years ago. Neither fossils nor molecular clocks correlate the origin of mitochondria, or eukaryogenesis more broadly, to either of these planetary redox transitions. Instead, mitochondria-bearing eukaryotes are consistently dated to between these two oxygenation events, during an interval of pervasive deep-sea anoxia and variable surface-water oxygenation. The discovery and cultivation of the Asgard archaea has reinforced metabolic evidence that eukaryogenesis was initially mediated by syntrophic H2 exchange between an archaeal host and an α-proteobacterial symbiont living under anoxia. Together, these results temporally, spatially and metabolically decouple the earliest stages of eukaryogenesis from the oxygen content of the surface ocean and atmosphere. Rather than reflecting the ancestral metabolic state, obligate aerobiosis in eukaryotes is most probably derived, having only become globally widespread over the past 1 billion years as atmospheric oxygen approached modern levels.
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