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Mohr W, Lehnen N, Ahmerkamp S, Marchant HK, Graf JS, Tschitschko B, Yilmaz P, Littmann S, Gruber-Vodicka H, Leisch N, Weber M, Lott C, Schubert CJ, Milucka J, Kuypers MMM. Terrestrial-type nitrogen-fixing symbiosis between seagrass and a marine bacterium. Nature 2021; 600:105-109. [PMID: 34732889 PMCID: PMC8636270 DOI: 10.1038/s41586-021-04063-4] [Citation(s) in RCA: 36] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2021] [Accepted: 09/22/2021] [Indexed: 01/23/2023]
Abstract
Symbiotic N2-fixing microorganisms have a crucial role in the assimilation of nitrogen by eukaryotes in nitrogen-limited environments1-3. Particularly among land plants, N2-fixing symbionts occur in a variety of distantly related plant lineages and often involve an intimate association between host and symbiont2,4. Descriptions of such intimate symbioses are lacking for seagrasses, which evolved around 100 million years ago from terrestrial flowering plants that migrated back to the sea5. Here we describe an N2-fixing symbiont, 'Candidatus Celerinatantimonas neptuna', that lives inside seagrass root tissue, where it provides ammonia and amino acids to its host in exchange for sugars. As such, this symbiosis is reminiscent of terrestrial N2-fixing plant symbioses. The symbiosis between Ca. C. neptuna and its host Posidonia oceanica enables highly productive seagrass meadows to thrive in the nitrogen-limited Mediterranean Sea. Relatives of Ca. C. neptuna occur worldwide in coastal ecosystems, in which they may form similar symbioses with other seagrasses and saltmarsh plants. Just like N2-fixing microorganisms might have aided the colonization of nitrogen-poor soils by early land plants6, the ancestors of Ca. C. neptuna and its relatives probably enabled flowering plants to invade nitrogen-poor marine habitats, where they formed extremely efficient blue carbon ecosystems7.
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Affiliation(s)
- Wiebke Mohr
- Max Planck Institute for Marine Microbiology, Bremen, Germany.
| | - Nadine Lehnen
- Max Planck Institute for Marine Microbiology, Bremen, Germany
| | | | | | - Jon S Graf
- Max Planck Institute for Marine Microbiology, Bremen, Germany
| | | | - Pelin Yilmaz
- Max Planck Institute for Marine Microbiology, Bremen, Germany
- Data Science Research Group, Institute for Artificial Intelligence in Medicine, University Hospital Essen, Essen, Germany
| | - Sten Littmann
- Max Planck Institute for Marine Microbiology, Bremen, Germany
| | | | - Nikolaus Leisch
- Max Planck Institute for Marine Microbiology, Bremen, Germany
| | | | | | - Carsten J Schubert
- Swiss Federal Institute of Aquatic Science and Technology (Eawag), Department of Surface Waters-Research and Management, Kastanienbaum, Switzerland
| | - Jana Milucka
- Max Planck Institute for Marine Microbiology, Bremen, Germany
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Graf JS, Schorn S, Kitzinger K, Ahmerkamp S, Woehle C, Huettel B, Schubert CJ, Kuypers MMM, Milucka J. Anaerobic endosymbiont generates energy for ciliate host by denitrification. Nature 2021; 591:445-450. [PMID: 33658719 PMCID: PMC7969357 DOI: 10.1038/s41586-021-03297-6] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2019] [Accepted: 01/27/2021] [Indexed: 11/27/2022]
Abstract
Mitochondria are specialized eukaryotic organelles that have a dedicated function in oxygen respiration and energy production. They evolved about 2 billion years ago from a free-living bacterial ancestor (probably an alphaproteobacterium), in a process known as endosymbiosis1,2. Many unicellular eukaryotes have since adapted to life in anoxic habitats and their mitochondria have undergone further reductive evolution3. As a result, obligate anaerobic eukaryotes with mitochondrial remnants derive their energy mostly from fermentation4. Here we describe 'Candidatus Azoamicus ciliaticola', which is an obligate endosymbiont of an anaerobic ciliate and has a dedicated role in respiration and providing energy for its eukaryotic host. 'Candidatus A. ciliaticola' contains a highly reduced 0.29-Mb genome that encodes core genes for central information processing, the electron transport chain, a truncated tricarboxylic acid cycle, ATP generation and iron-sulfur cluster biosynthesis. The genome encodes a respiratory denitrification pathway instead of aerobic terminal oxidases, which enables its host to breathe nitrate instead of oxygen. 'Candidatus A. ciliaticola' and its ciliate host represent an example of a symbiosis that is based on the transfer of energy in the form of ATP, rather than nutrition. This discovery raises the possibility that eukaryotes with mitochondrial remnants may secondarily acquire energy-providing endosymbionts to complement or replace functions of their mitochondria.
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Affiliation(s)
- Jon S Graf
- Max Planck Institute for Marine Microbiology, Bremen, Germany.
| | - Sina Schorn
- Max Planck Institute for Marine Microbiology, Bremen, Germany
| | - Katharina Kitzinger
- Max Planck Institute for Marine Microbiology, Bremen, Germany
- Division of Microbial Ecology, Centre for Microbiology and Environmental Systems Science, University of Vienna, Vienna, Austria
| | | | - Christian Woehle
- Max Planck Genome Centre Cologne, Max Planck Institute for Plant Breeding Research, Cologne, Germany
| | - Bruno Huettel
- Max Planck Genome Centre Cologne, Max Planck Institute for Plant Breeding Research, Cologne, Germany
| | - Carsten J Schubert
- Surface Waters - Research and Management, Eawag, Kastanienbaum, Switzerland
| | | | - Jana Milucka
- Max Planck Institute for Marine Microbiology, Bremen, Germany.
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Graf JS, Mayr MJ, Marchant HK, Tienken D, Hach PF, Brand A, Schubert CJ, Kuypers MMM, Milucka J. Bloom of a denitrifying methanotroph, 'Candidatus Methylomirabilis limnetica', in a deep stratified lake. Environ Microbiol 2018; 20:2598-2614. [PMID: 29806730 DOI: 10.1111/1462-2920.14285] [Citation(s) in RCA: 51] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2017] [Revised: 04/03/2018] [Accepted: 04/04/2018] [Indexed: 12/17/2022]
Abstract
Methanotrophic bacteria represent an important biological filter regulating methane emissions into the atmosphere. Planktonic methanotrophic communities in freshwater lakes are typically dominated by aerobic gamma-proteobacteria, with a contribution from alpha-proteobacterial methanotrophs and the NC10 bacteria. The NC10 clade encompasses methanotrophs related to 'Candidatus Methylomirabilis oxyfera', which oxidize methane using a unique pathway of denitrification that tentatively produces N2 and O2 from nitric oxide (NO). Here, we describe a new species of the NC10 clade, 'Ca. Methylomirabilis limnetica', which dominated the planktonic microbial community in the anoxic depths of the deep stratified Lake Zug in two consecutive years, comprising up to 27% of the total bacterial population. Gene transcripts assigned to 'Ca. M. limnetica' constituted up to one third of all metatranscriptomic sequences in situ. The reconstructed genome encoded a complete pathway for methane oxidation, and an incomplete denitrification pathway, including two putative nitric oxide dismutase genes. The genome of 'Ca. M. limnetica' exhibited features possibly related to genome streamlining (i.e. less redundancy of key metabolic genes) and adaptation to its planktonic habitat (i.e. gas vesicle genes). We speculate that 'Ca. M. limnetica' temporarily bloomed in the lake during non-steady-state conditions suggesting a niche for NC10 bacteria in the lacustrine methane and nitrogen cycle.
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Affiliation(s)
- Jon S Graf
- Max-Planck-Institute for Marine Microbiology, Department of Biogeochemistry, Bremen, Germany
| | - Magdalena J Mayr
- Eawag, Surface Waters-Research and Management, Kastanienbaum, Switzerland.,ETH Zurich, Institute of Biogeochemistry and Pollutant Dynamics, Zürich, Switzerland
| | - Hannah K Marchant
- Max-Planck-Institute for Marine Microbiology, Department of Biogeochemistry, Bremen, Germany
| | - Daniela Tienken
- Max-Planck-Institute for Marine Microbiology, Department of Biogeochemistry, Bremen, Germany
| | - Philipp F Hach
- Max-Planck-Institute for Marine Microbiology, Department of Biogeochemistry, Bremen, Germany
| | - Andreas Brand
- Eawag, Surface Waters-Research and Management, Kastanienbaum, Switzerland.,ETH Zurich, Institute of Biogeochemistry and Pollutant Dynamics, Zürich, Switzerland
| | - Carsten J Schubert
- Eawag, Surface Waters-Research and Management, Kastanienbaum, Switzerland
| | - Marcel M M Kuypers
- Max-Planck-Institute for Marine Microbiology, Department of Biogeochemistry, Bremen, Germany
| | - Jana Milucka
- Max-Planck-Institute for Marine Microbiology, Department of Biogeochemistry, Bremen, Germany
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Abstract
This series of experiments analyzes the role of learning in the development of pecking in ring dove squab. Experiment 1 showed that there is a high probability that parents will feed squab after a period of separation (Experiment 1). Such feedings may have been essential for producing the previous observation (Graf, Balsam, & Silver, 1985) that pecking develops normally if squab which have been separated from their parents are given a daily 20-min interaction with seed followed by an immediate return to their parents. Experiment 2 showed that exposure to seed followed by experimenter-provided feedings were sufficient for inducing adult pecking levels. Experiment 3 showed that general experience with conspecifics was not necessary for the development of pecking and that maturation alone could not account for the pecking observed in previous experiments. Experiment 4 showed that Pavlovian contingencies consisting of visual exposure to seed followed by feeding was sufficient to induce high levels of pecking. There did not appear to be an additional contribution of an operant contingency present when squab were allowed to both see and peck at seed prior to feedings in Experiment 5. However, squab must actually be given experience in handling and ingesting seeds before adult levels of pecking can be obtained. These results are discussed in terms of the developmental pathways whereby experience leads to adult behavior.
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Affiliation(s)
- P D Balsam
- Department of Psychology, Barnard College, Columbia University, New York, NY 10027
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Abstract
In these studies, descriptive information on the diet and feeding behavior of ring dove squab is considered in the context of an analysis of the mechanisms underlying the development of eating. Experiment I shows that squab begin to peck at grain around Day 13 and both the rate and efficiency of pecking increase through Day 21 when the squab are weaned. Experiment II shows that squab reared without seed in their home cage do not develop normal levels of pecking unless exposure to seed is followed in close temporal proximity by interaction with parents. It is concluded that an association between some aspect of squab's interaction with seed and a parentally provided unconditioned stimulus is sufficient for normal pecking to develop. The nature of these associations and their contribution to the ontogeny of independent feeding are discussed.
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