Project highlights

  • Use cutting techniques to measure photosynthesis.
  • Test how abiotic and biotic stress impact photosynthesis of marine phytoplankton.
  • Through collaboration, translate measurements into predictive models of ocean carbon cycle. 

Overview

Virtually all life on Earth depends on photosynthesis and this fundamental process is a major component of the carbon cycle and therefore climate change. Roughly half of photosynthesis occurs in the Oceans, where the most dominant phototrophs are the single-celled cyanobacteria Prochlorococcus and Synechococcus. These organisms thrive from shelf seas to open ocean and from the tropics to poles. They evolved ~1 billion years ago into several “ecotypes”, each with specific adaptations to their niche. Across these gradients, there are several stressors that might affect photosynthesis including light, temperature, and severely limiting macronutients (nitrogen and phoshphorus) and micronutrients (metals and vitamins). Yet how the photosynthetic apparatus has evolved to these different stressors has not yet been studied in these organisms. 

The photosynthetic apparatus is composed of two processes: the light and dark reactions. The light reactions are a series of electron transport processes that together oxidise water and reduce NADP using the energy from light. In so doing, they produce NADPH and ATP that together fuel the dark reactions; the Calvin Benson cycle that fixes carbon dioxide. These two reactions are ‘coupled’, but this coupling depends on both environmental stress and genetically encoded factors that alter this coupling. Yet we lack a basic understanding of how and why these reactions may become decoupled.  

We have an extensive collection of isolates of Prochlorococcus and Synechococcus, each with a full genome sequence. Moreover, we have a full understanding of their distribution across Earth’s oceans. Yet, so far, we have been unable to link these data with the fundamental activity of photosynthesis. In this project, you will make cutting edge measurements of photosynthetic electron transport and carbon fixation from these organisms in the lab under different stress conditions. You will then use AI techniques to link these activities with genome sequences and gene expression data. Lastly, you will integrate these data with distributions of these organisms in the Ocean with in-situ measurements of photosynthesis to develop predictive models to improve our ability to measure photosynthesis and predict Earth’s response to climate change. 

Host

University of Warwick

Theme

  • Climate and Environmental Sustainability
  • Organisms and Ecosystems

Supervisors

Project investigator

Co-investigators

How to apply

Methodology

You will use a combination of cutting-edge biophysical measurements to measure photosynthetic electron transport including fast-repetition rate fluorescence and Joliot type pump-probe spectroscopy. You will link these with high-throughput radiotracer techniques to measure carbon fixation.  

Training and skills

Training will be provided in the above techniques that have been developed in the Puxty and Bibby labs. In addition to the above you will learn techniques like: flow cytometry, genetic engineering, mass-spectrometry, transcriptomics and metagenomics. 

DRs will be awarded CENTA Training Credits (CTCs) for participation in CENTA-provided and ‘free choice’ external training. One CTC can be earned per 3 hours training, and DRs must accrue 100 CTCs across the three and a half years of their PhD.  

Partners and collaboration

The supervisors are world-leading experts in marine molecular biology. We frequently publish in high profile interdisciplinary journals (e.g. Nature Plants, Current Biology, Proc. Natl. Acad. Sci. USA) and field specific high impact journals (e.g. The ISME Journal). You will belong to a larger group of environmental microbiologists in the department of life sciences’ environment theme.  These groups occupy a large shared lab area and as such there is continuous collaborations and opportunities for career development within the theme. Current research in the groups is funded by NERC. 

Dr Puxty’s group: https://warwick.ac.uk/fac/sci/lifesci/people/rpuxty/ 

Prof Bibby’s group: https://www.southampton.ac.uk/people/5x2k2m/professor-tom-bibby   

Further details

Informal enquiries can be made to Dr Richard Puxty ([email protected]).

To apply to this project: 

  • You must include a CV with the names of at least two referees (preferably three) who can comment on your academic abilities.  

 Applications must be submitted by 23:59 GMT on Wednesday 8th January 2025.  

Possible timeline

Year 1

Perform high-throughput measurements of carbon fixation and photosynthetic light reactions.

Year 2

Understand how abiotic stress affects coupling of light and dark reactions.

Year 3

Use AI modelling to measure the relationship between photosynthesis and genetics. 

Further reading

[1] Scanlan DJ, Ostrowski M, Mazard S, Dufresne A, Garczarek L, Hess WR, Post AF, Hagemann M, Paulsen I, Partensky F. 2009. Ecological Genomics of Marine Picocyanobacteria. Microbiol Mol Biol Rev 73: doi: 10.1128/mmbr.00035-08  

[2] Jonathan P. Zehr, Raphael M. Kudela. 2009.Photosynthesis in the Open Ocean. Science326,945-946.DOI:10.1126/science.1181277 

[3] Suggett DJ., Oxborough K., Baker NR, MacIntyre HL, Kana TM, & Geider, RJ. 2003. Fast repetition rate and pulse amplitude modulation chlorophyll a fluorescence measurements for assessment of photosynthetic electron transport in marine phytoplankton. European Journal of Phycology, 38(4), 371–384. doi: 10.1080/09670260310001612655 

[4] Viola S, Bailleul B, Yu J, Nixon P, Selles J, Wollman F-A. 2019. Probing the electric field across thylakoid membranes in cyanobacteria. PNAS 116 (43) 21900-21906 doi:10.1073/pnas.1913099116