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Jenkins BH. Mutualism on the edge: Understanding the Paramecium-Chlorella symbiosis. PLoS Biol 2024; 22:e3002563. [PMID: 38573881 PMCID: PMC10994274 DOI: 10.1371/journal.pbio.3002563] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/06/2024] Open
Abstract
Exploring the mechanisms that underpin symbiosis requires an understanding of how these complex interactions are maintained in diverse model systems. The ciliate protist, Paramecium bursaria, offers a valuable insight into how emergent endosymbiotic interactions have evolved.
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Affiliation(s)
- Benjamin H. Jenkins
- Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
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Osvatic JT, Yuen B, Kunert M, Wilkins L, Hausmann B, Girguis P, Lundin K, Taylor J, Jospin G, Petersen JM. Gene loss and symbiont switching during adaptation to the deep sea in a globally distributed symbiosis. THE ISME JOURNAL 2023; 17:453-466. [PMID: 36639537 PMCID: PMC9938160 DOI: 10.1038/s41396-022-01355-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/09/2022] [Revised: 12/16/2022] [Accepted: 12/21/2022] [Indexed: 01/14/2023]
Abstract
Chemosynthetic symbioses between bacteria and invertebrates occur worldwide from coastal sediments to the deep sea. Most host groups are restricted to either shallow or deep waters. In contrast, Lucinidae, the most species-rich family of chemosymbiotic invertebrates, has both shallow- and deep-sea representatives. Multiple lucinid species have independently colonized the deep sea, which provides a unique framework for understanding the role microbial symbionts play in evolutionary transitions between shallow and deep waters. Lucinids acquire their symbionts from their surroundings during early development, which may allow them to flexibly acquire symbionts that are adapted to local environments. Via metagenomic analyses of museum and other samples collected over decades, we investigated the biodiversity and metabolic capabilities of the symbionts of 22 mostly deep-water lucinid species. We aimed to test the theory that the symbiont played a role in adaptation to life in deep-sea habitats. We identified 16 symbiont species, mostly within the previously described genus Ca. Thiodiazotropha. Most genomic functions were shared by both shallow-water and deep-sea Ca. Thiodiazotropha, though nitrogen fixation was exclusive to shallow-water species. We discovered multiple cases of symbiont switching near deep-sea hydrothermal vents and cold seeps, where distantly related hosts convergently acquired novel symbionts from a different bacterial order. Finally, analyses of selection revealed consistently stronger purifying selection on symbiont genomes in two extreme habitats - hydrothermal vents and an oxygen-minimum zone. Our findings reveal that shifts in symbiont metabolic capability and, in some cases, acquisition of a novel symbiont accompanied adaptation of lucinids to challenging deep-sea habitats.
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Affiliation(s)
- Jay T. Osvatic
- grid.10420.370000 0001 2286 1424University of Vienna, Centre for Microbiology and Environmental Systems Science, Department for Microbiology and Ecosystem Science, Division of Microbial Ecology, Djerassiplatz 1, 1030 Vienna, Austria ,University of Venna, Doctoral School in Microbiology and Environmental Science, Djerassiplatz 1, 1030 Vienna, Austria
| | - Benedict Yuen
- grid.10420.370000 0001 2286 1424University of Vienna, Centre for Microbiology and Environmental Systems Science, Department for Microbiology and Ecosystem Science, Division of Microbial Ecology, Djerassiplatz 1, 1030 Vienna, Austria
| | - Martin Kunert
- grid.10420.370000 0001 2286 1424University of Vienna, Centre for Microbiology and Environmental Systems Science, Department for Microbiology and Ecosystem Science, Division of Microbial Ecology, Djerassiplatz 1, 1030 Vienna, Austria
| | - Laetitia Wilkins
- grid.419529.20000 0004 0491 3210Eco-Evolutionary Interactions Group, Max Planck Institute for Marine Microbiology, Celsiusstrasse 1, 28209 Bremen, Germany
| | - Bela Hausmann
- grid.10420.370000 0001 2286 1424Joint Microbiome Facility of the Medical University of Vienna and the University of Vienna, 1030 Vienna, Austria ,grid.22937.3d0000 0000 9259 8492Department of Laboratory Medicine, Medical University of Vienna, 1090 Vienna, Austria
| | - Peter Girguis
- grid.38142.3c000000041936754XDepartment of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138 USA
| | - Kennet Lundin
- grid.516430.50000 0001 0059 3334Gothenburg Natural History Museum, Box 7283, 40235 Gothenburg, Sweden ,grid.8761.80000 0000 9919 9582Gothenburg Global Biodiversity Centre, Box 461, 40530 Gothenburg, Sweden
| | - John Taylor
- grid.35937.3b0000 0001 2270 9879Natural History Museum, Cromwell Rd, London, SW7 5BD UK
| | | | - Jillian M. Petersen
- grid.10420.370000 0001 2286 1424University of Vienna, Centre for Microbiology and Environmental Systems Science, Department for Microbiology and Ecosystem Science, Division of Microbial Ecology, Djerassiplatz 1, 1030 Vienna, Austria
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Takahashi T. Method for Stress Assessment of Endosymbiotic Algae in Paramecium bursaria as a Model System for Endosymbiosis. Microorganisms 2022; 10:microorganisms10061248. [PMID: 35744766 PMCID: PMC9228868 DOI: 10.3390/microorganisms10061248] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2022] [Revised: 06/11/2022] [Accepted: 06/14/2022] [Indexed: 12/04/2022] Open
Abstract
Endosymbiosis between heterotrophic host and microalga often breaks down because of environmental conditions, such as temperature change and exposure to toxic substances. By the time of the apparent breakdown of endosymbiosis, it is often too late for the endosymbiotic system to recover. In this study, I developed a technique for the stress assessment of endosymbiotic algae using Paramecium bursaria as an endosymbiosis model, after treatment with the herbicide paraquat, an endosymbiotic collapse inducer. Microcapillary flow cytometry was employed to evaluate a large number of cells in an approach that is more rapid than microscopy evaluation. In the assay, red fluorescence of the chlorophyll reflected the number of endosymbionts within the host cell, while yellow fluorescence fluctuated in response to the deteriorating viability of the endosymbiont under stress. Hence, the yellow/red fluorescence intensity ratio can be used as an algal stress index independent of the algal number. An optical evaluation revealed that the viability of the endosymbiotic algae within the host cell decreased after treatment with paraquat and that the remaining endosymbionts were exposed to high stress. The devised assay is a potential environmental monitoring method, applicable not only to P. bursaria but also to multicellular symbiotic units, such as corals.
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Affiliation(s)
- Toshiyuki Takahashi
- Department of Chemical Science and Engineering, National Institute of Technology (KOSEN), Miyakonojo College, Miyazaki 885-8567, Japan
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Emergent RNA-RNA interactions can promote stability in a facultative phototrophic endosymbiosis. Proc Natl Acad Sci U S A 2021; 118:2108874118. [PMID: 34521754 PMCID: PMC8463893 DOI: 10.1073/pnas.2108874118] [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] [Accepted: 07/15/2021] [Indexed: 12/11/2022] Open
Abstract
Stable endosymbiosis between eukaryotic microbes has driven the evolution of further cellular complexity. Yet the mechanisms that can act to stabilize an emergent eukaryote–eukaryote endosymbiosis are unclear. Using the model facultative endosymbiotic system, Paramecium bursaria, we demonstrate that endosymbiont–host RNA–RNA interactions can drive a cost to host growth upon endosymbiont digestion. These RNA–RNA interactions are facilitated by the host RNA-interference system. For endosymbiont messenger RNA sharing a high level of sequence identity with host transcripts, this process can result in host gene knockdown. We propose that these endosymbiont–host RNA–RNA interactions—“RNA-interference collisions”—represent an emergent mechanism to sanction the host for breakdown of the endosymbiosis, promoting the stability of the facultative endosymbiotic interaction. Eukaryote–eukaryote endosymbiosis was responsible for the spread of chloroplast (plastid) organelles. Stability is required for the metabolic and genetic integration that drives the establishment of new organelles, yet the mechanisms that act to stabilize emergent endosymbioses—between two fundamentally selfish biological organisms—are unclear. Theory suggests that enforcement mechanisms, which punish misbehavior, may act to stabilize such interactions by resolving conflict. However, how such mechanisms can emerge in a facultative endosymbiosis has yet to be explored. Here, we propose that endosymbiont–host RNA–RNA interactions, arising from digestion of the endosymbiont population, can result in a cost to host growth for breakdown of the endosymbiosis. Using the model facultative endosymbiosis between Paramecium bursaria and Chlorella spp., we demonstrate that this mechanism is dependent on the host RNA-interference (RNAi) system. We reveal through small RNA (sRNA) sequencing that endosymbiont-derived messenger RNA (mRNA) released upon endosymbiont digestion can be processed by the host RNAi system into 23-nt sRNA. We predict multiple regions of shared sequence identity between endosymbiont and host mRNA, and demonstrate through delivery of synthetic endosymbiont sRNA that exposure to these regions can knock down expression of complementary host genes, resulting in a cost to host growth. This process of host gene knockdown in response to endosymbiont-derived RNA processing by host RNAi factors, which we term “RNAi collisions,” represents a mechanism that can promote stability in a facultative eukaryote–eukaryote endosymbiosis. Specifically, by imposing a cost for breakdown of the endosymbiosis, endosymbiont–host RNA–RNA interactions may drive maintenance of the symbiosis across fluctuating ecological conditions.
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Abstract
Can hosts swap ancient symbionts for new ones? A new study shows that a novel partnership between a protist and an algal symbiont can rapidly evolve to both overcome initial incompatibility and adapt to environmental challenges.
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Affiliation(s)
- Stephanie Porter
- School of Biological Sciences, Washington State University, Vancouver, WA 98686, USA.
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