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Moulin SLY, Frail S, Braukmann T, Doenier J, Steele-Ogus M, Marks JC, Mills MM, Yeh E. The endosymbiont of Epithemia clementina is specialized for nitrogen fixation within a photosynthetic eukaryote. ISME COMMUNICATIONS 2024; 4:ycae055. [PMID: 38707843 PMCID: PMC11070190 DOI: 10.1093/ismeco/ycae055] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/09/2024] [Revised: 04/05/2024] [Accepted: 04/08/2024] [Indexed: 05/07/2024]
Abstract
Epithemia spp. diatoms contain obligate, nitrogen-fixing endosymbionts, or diazoplasts, derived from cyanobacteria. These algae are a rare example of photosynthetic eukaryotes that have successfully coupled oxygenic photosynthesis with oxygen-sensitive nitrogenase activity. Here, we report a newly-isolated species, E. clementina, as a model to investigate endosymbiotic acquisition of nitrogen fixation. We demonstrate that the diazoplast, which has lost photosynthesis, provides fixed nitrogen to the diatom host in exchange for fixed carbon. To identify the metabolic changes associated with this endosymbiotic specialization, we compared the Epithemia diazoplast with its close, free-living cyanobacterial relative, Crocosphaera subtropica. Unlike C. subtropica, in which nitrogenase activity is temporally separated from photosynthesis, we show that nitrogenase activity in the diazoplast is continuous through the day (concurrent with host photosynthesis) and night. Host and diazoplast metabolism are tightly coupled to support nitrogenase activity: Inhibition of photosynthesis abolishes daytime nitrogenase activity, while nighttime nitrogenase activity no longer requires cyanobacterial glycogen storage pathways. Instead, import of host-derived carbohydrates supports nitrogenase activity throughout the day-night cycle. Carbohydrate metabolism is streamlined in the diazoplast compared to C. subtropica with retention of the oxidative pentose phosphate pathway and oxidative phosphorylation. Similar to heterocysts, these pathways may be optimized to support nitrogenase activity, providing reducing equivalents and ATP and consuming oxygen. Our results demonstrate that the diazoplast is specialized for endosymbiotic nitrogen fixation. Altogether, we establish a new model for studying endosymbiosis, perform a functional characterization of this diazotroph endosymbiosis, and identify metabolic adaptations for endosymbiotic acquisition of a critical biological function.
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Affiliation(s)
- Solène L Y Moulin
- Department of Pathology, Stanford School of Medicine, Stanford, CA 94305, United States
| | - Sarah Frail
- Department of Biochemistry, Stanford School of Medicine, Stanford, CA 94305, United States
| | - Thomas Braukmann
- Department of Pathology, Stanford School of Medicine, Stanford, CA 94305, United States
- Department of Biochemistry, Stanford School of Medicine, Stanford, CA 94305, United States
| | - Jon Doenier
- Department of Biochemistry, Stanford School of Medicine, Stanford, CA 94305, United States
| | - Melissa Steele-Ogus
- Department of Pathology, Stanford School of Medicine, Stanford, CA 94305, United States
| | - Jane C Marks
- Department of Biological Sciences, Northern Arizona University, Flagstaff, AR 86011, United States
- Center for Ecosystem Science and Society, Northern Arizona University, Flagstaff, AZ 86011, United States
| | - Matthew M Mills
- Department of Earth System Science, Stanford Doerr School of Sustainability, Stanford, CA 94305, United States
| | - Ellen Yeh
- Department of Pathology, Stanford School of Medicine, Stanford, CA 94305, United States
- Department of Microbiology & Immunology, Stanford School of Medicine, Stanford, CA 94305, United States
- Chan Zuckerberg Biohub, San Francisco, CA 94158, United States
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Li X, Bao N, Yan Z, Yuan XZ, Wang SG, Xia PF. Degradation of Antibiotic Resistance Genes by VADER with CRISPR-Cas Immunity. Appl Environ Microbiol 2023; 89:e0005323. [PMID: 36975789 PMCID: PMC10132114 DOI: 10.1128/aem.00053-23] [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: 01/12/2023] [Accepted: 03/03/2023] [Indexed: 03/29/2023] Open
Abstract
The evolution and dissemination of antibiotic resistance genes (ARGs) are prompting severe health and environmental issues. While environmental processes, e.g., biological wastewater treatment, are key barriers to prevent the spread of ARGs, they are often sources of ARGs at the same time, requiring upgraded biotechnology. Here, we present VADER, a synthetic biology system for the degradation of ARGs based on CRISPR-Cas immunity, an archaeal and bacterial immune system for eliminating invading foreign DNAs, to be implemented for wastewater treatment processes. Navigated by programmable guide RNAs, VADER targets and degrades ARGs depending on their DNA sequences, and by employing an artificial conjugation machinery, IncP, it can be delivered via conjugation. The system was evaluated by degrading plasmid-borne ARGs in Escherichia coli and further demonstrated via the elimination of ARGs on the environmentally relevant RP4 plasmid in Pseudomonas aeruginosa. Next, a prototype conjugation reactor at a 10-mL scale was devised, and 100% of the target ARG was eliminated in the transconjugants receiving VADER, giving a proof of principle for the implementation of VADER in bioprocesses. By generating a nexus of synthetic biology and environmental biotechnology, we believe that our work is not only an enterprise for tackling ARG problems but also a potential solution for managing undesired genetic materials in general in the future. IMPORTANCE Antibiotic resistance has been causing severe health problems and has led to millions of deaths in recent years. Environmental processes, especially those of the wastewater treatment sector, are an important barrier to the spread of antibiotic resistance from the pharmaceutical industry, hospitals, or civil sewage. However, they have been identified as a nonnegligible source of antibiotic resistance at the same time, as antibiotic resistance with its main cause, antibiotic resistance genes (ARGs), may accumulate in biological treatment units. Here, we transplanted the CRISPR-Cas system, an immune system via programmable DNA cleavage, to tackle the antibiotic resistance problem raised in wastewater treatment processes, and we propose a new sector specialized in ARG removal with a conjugation reactor to implement the CRISPR-Cas system. Our study provides a new angle for resolving public health issues via the implementation of synthetic biology in environmental contexts at the process level.
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Affiliation(s)
- Xin Li
- Shandong Key Laboratory of Water Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Shandong University, Qingdao, China
| | - Nan Bao
- Shandong Key Laboratory of Water Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Shandong University, Qingdao, China
| | - Zhen Yan
- Shandong Key Laboratory of Water Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Shandong University, Qingdao, China
| | - Xian-Zheng Yuan
- Shandong Key Laboratory of Water Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Shandong University, Qingdao, China
- Sino-French Research Institute for Ecology and Environment, Shandong University, Qingdao, China
| | - Shu-Guang Wang
- Shandong Key Laboratory of Water Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Shandong University, Qingdao, China
- Sino-French Research Institute for Ecology and Environment, Shandong University, Qingdao, China
| | - Peng-Fei Xia
- Shandong Key Laboratory of Water Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Shandong University, Qingdao, China
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Moulin SL, Frail S, Doenier J, Braukmann T, Yeh E. The endosymbiont of Epithemia clementina is specialized for nitrogen fixation within a photosynthetic eukaryote. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.03.08.531752. [PMID: 37066385 PMCID: PMC10103950 DOI: 10.1101/2023.03.08.531752] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 06/19/2023]
Abstract
Epithemia spp. diatoms contain obligate, nitrogen-fixing endosymbionts, or "diazoplasts", derived from cyanobacteria. These algae are a rare example of photosynthetic eukaryotes that have successfully coupled oxygenic photosynthesis with oxygen-sensitive nitrogenase activity. Here, we report a newly-isolated species, E. clementina, as a model to investigate endosymbiotic acquisition of nitrogen fixation. To detect the metabolic changes associated with endosymbiotic specialization, we compared nitrogen fixation, associated carbon and nitrogen metabolism, and their regulatory pathways in the Epithemia diazoplast with its close, free-living cyanobacterial relative, Crocosphaera subtropica. Unlike C. subtropica, we show that nitrogenase activity in the diazoplast is concurrent with, and even dependent on, host photosynthesis and no longer associated with cyanobacterial glycogen storage suggesting carbohydrates are imported from the host diatom. Carbohydrate catabolism in the diazoplast indicates that the oxidative pentose pathway and oxidative phosphorylation, in concert, generates reducing equivalents and ATP and consumes oxygen to support nitrogenase activity. In contrast to expanded nitrogenase activity, the diazoplast has diminished ability to utilize alternative nitrogen sources. Upon ammonium repletion, negative feedback regulation of nitrogen fixation was conserved, however ammonia assimilation showed paradoxical responses in the diazoplast compared with C. subtropica. The altered nitrogen regulation likely favors nitrogen transfer to the host. Our results suggest that the diazoplast is specialized for endosymbiotic nitrogen fixation. Altogether, we establish a new model for studying endosymbiosis, perform the first functional characterization of this diazotroph endosymbiosis, and identify metabolic adaptations for endosymbiotic acquisition of a critical biological function.
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Affiliation(s)
- Solène L.Y. Moulin
- Department of Pathology, Stanford School of Medicine, Stanford, California, USA
| | - Sarah Frail
- Department of Biochemistry, Stanford School of Medicine, Stanford, California, USA
| | - Jon Doenier
- Department of Biochemistry, Stanford School of Medicine, Stanford, California, USA
| | - Thomas Braukmann
- Department of Pathology, Stanford School of Medicine, Stanford, California, USA
- Department of Biochemistry, Stanford School of Medicine, Stanford, California, USA
| | - Ellen Yeh
- Department of Pathology, Stanford School of Medicine, Stanford, California, USA
- Department of Microbiology & Immunology, Stanford School of Medicine, Stanford, California, USA
- Chan Zuckerberg Biohub – San Francisco, San Francisco, CA 94158
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LeBoldus JM, Navarro SM, Kline N, Ritokova G, Grünwald NJ. Repeated Emergence of Sudden Oak Death in Oregon: Chronology, Impact, and Management. PLANT DISEASE 2022; 106:3013-3021. [PMID: 35486603 DOI: 10.1094/pdis-02-22-0294-fe] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
It has been two decades since the first detection of the sudden oak death pathogen Phytophthora ramorum in Oregon forests. Although the epidemic was managed since its first discovery in 2001, at least three invasions of three separate variants (clonal lineages), NA1, EU1, and NA2, are documented to have occurred to date. Control of this epidemic has cost over US$32 million from 2001 to 2020. This is dwarfed by the predicted cost of the closure to the Coos Bay export terminal, estimated at $58 million per year, if the epidemic was allowed to spread unchecked. Management efforts in Oregon have reduced inoculum and limited the spread of the pathogen. An outreach and citizen scientist program has been piloted to help in early detection efforts and search for disease-resistant tanoak. This feature article documents the repeated emergence, impact, costs, and lessons learned from managing this devastating invasive pathogen.
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Affiliation(s)
- Jared M LeBoldus
- Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR
- Forest Engineering, Resources and Management Department, Oregon State University, Corvallis, OR
| | | | - Norma Kline
- Forest Engineering, Resources and Management Department, Oregon State University, Corvallis, OR
| | | | - Niklaus J Grünwald
- Horticultural Crops Research Laboratory, United States Department of Agriculture-Agricultural Research Service, Corvallis, OR
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Life 2.0-A CRISPR path to a sustainable planet. Proc Natl Acad Sci U S A 2021; 118:2107418118. [PMID: 34050031 DOI: 10.1073/pnas.2107418118] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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