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Cambridge NERC Doctoral Training Partnerships

Graduate Research Opportunities

Lead Supervisor: Jenny Zhang, Chemistry

Co-Supervisor: Christopher Howe, Biochemistry

Brief summary: 
This project aims to understand how climate change can lead to coral bleaching by unpicking the redox triggers that lead to the expulsion of the photosynthetic microorganism, dinoflagellates, from corals.
Importance of the area of research concerned: 
Coral bleaching is one of the most obvious environmental catastrophes facing the planet as a result of climate change. Coral animals rely on symbiosis with intracellular dinoflagellate algae. The dinoflagellates provide the host with photosynthetically fixed carbon, and receive other nutrients and physical protection in return. This symbiosis breaks down under some conditions, including raised temperatures, resulting in expulsion of the dinoflagellates and bleaching. We urgently need to understand the molecular trigger(s) for expulsion. It is thought there is a disturbance in the light reactions of photosynthesis, but the details of this are still not clear. We have been developing powerful new tools for studying photosynthesis, including the use of extracellular electron export from photosynthetic cells (exoelectrogenesis), which reports on photosynthetic function inside the cells. In the case of dinoflagellates and corals, exoelectrogenesis by the former to the host may also play a direct role in the symbiosis. Studying the effects of environmental conditions believed to trigger bleaching on exoelectrogenesis will make a major contribution to our understanding of bleaching.
Project summary : 
All photosynthetic microorganisms exhibit exoelectrogenesis, where electrons from photosynthesis are exported extracellularly. We, in collaboration with Chris Howe (Biochemistry, Cambridge), have developed systems for accurate measurements of exoelectrogenesis, including how it is affected by changes in environmental factors such as light, pH and temperature. The project will measure exoelectrogenesis by the dinoflagellate Symbiodinium, the genus whose members form symbiosis with corals. It will study how external stresses may disturb photosynthesis, affecting redox signalling via exoelectrogenesis. Several mutant cell lines are available in which photosynthesis has been directly compromised, these will be included in the study. Overall, the project will provide direct indications of how disturbance of photosynthesis affects the redox exchange between dinoflagellates and their hosts.
What will the student do?: 
The student will grow dinoflagellate algae of the genus Symbiodinium under a range of conditions, e.g. varying in light intensity, pH and temperature. They will use state-of-the-art biophotoelectrochemical, spectroscopy and microscopy systems we have established to measure electron exchange between cells and coral-mimicking electrodes under those conditions, comparing the results with other measures of photosynthetic function, e.g. oxygen evolution and generation of reactive oxygen species. Comparison with controls grown under standard conditions will indicate if factors implicated in coral bleaching, such as elevated temperature, affect electron export. We have a range of mutant lines of Symbiodinium available with varying degrees of genetic impairment of photosynthesis. The student will determine the effects of these impairments on exoelectrogenesis. Attempts will also be made to complement the mutant lines to test the effects of modifying the photosynthetic electron transfer chain on exoelectrogenesis.
References - references should provide further reading about the project: 
Slavov, C. et al. 2016. “Super-quenching” state protects Symbiodinium from thermal stress - Implications for coral bleaching. Biochimica et Biophysica Acta (BBA) – Bioenergetics, vol. 1857, pp. 840-847.,
Nimmo, I.C. et al. 2019. Genetic transformation of the dinoflagellate chloroplast. eLife vol. 8, pp e45292
Wey, L. T., et al. 2019. The Development of Biophotovoltaic Systems for Power Generation and Biological Analysis – ChemElectroChem, vol. 6, pp 5375-5386 DOI: 10.1002/celc.201900997
You can find out about applying for this project on the Department of Chemistry page.
Department of Chemistry Graduate Administrator