Project highlights
- Resolving unknown effects of nitrogen (N) and nitrogen-phosphorus (N/P) co-limitation on lipid synthesis
- State of the art lipidomics and proteomics
- Assessment of carbon fixation under future ocean nutrient conditions
Overview
Marine phytoplankton counteract global climate change by fixing about half of atmospheric carbon dioxide. Yet, their growth depends on nutrient availability with the key macronutrient nitrogen (N) often limiting marine productivity, while others such as phosphorus (P) can have a co-limiting effect (Moore et al. 2013). Due to climate change, stratification of ocean waters increases thereby expanding nutrient limiting conditions.
Phytoplankton incorporate nutrients into their biomass forming macromolecules such as membrane lipids, the cell’s barrier towards the environment. To reduce their cellular P quota, phytoplankton substitute phospholipids for non-P-containing lipids e.g. N-containing betaine lipids under P limitation (Van Mooy et al. 2009). Our lab found that this lipid remodelling affects the ecophysiology of the diatom Phaeodactylum tricornutum (Mausz et al. in prep.), and remodelled bacteria were more susceptible to digestion by grazers (Guillonneau et al. 2022). In contrast, our knowledge on the effect of N limitation is limited. While in P. tricornutum N limitation significantly increased triacylglycerol production, ecophysiological consequences were not tested (Abida et al. 2015). But ecological effects are likely as in bacteria the knockout of a N-containing aminolipid changed nutrient uptake efficiency (Stirrup et al. 2023).
This project will use laboratory culture experiments to fill the knowledge gap regarding how N limitation affects lipid biosynthesis and cell ecophysiology in the globally important phytoplankton groups diatoms and prymnesiophytes.
Therefore, using liquid chromatography-mass spectrometry, the project aims to determine changes in lipid composition of representatives of both diatoms (e.g. Phaeodactylum tricornutum, Thalassiosira pseudonana) and prymnesiophytes (e.g. Gephyrocapsa huxleyi, Isochrysis galbana) following N and N/P (co-)limitation. Further, it will establish consequences of lipid remodelling on cell ecophysiology and protein expression. For ecophysiology, we will focus on photosynthesis capability and motility – the former determines carbon fixation rates, while the latter determines the ability for chemotaxis and to find mates (Wetherbee et al., 2002; Bondoc et al., 2016). Therefore, we will use established mass spectrometry, photophysiology, and fluorescent time-lapse microscopy platforms (see Methodology). By generating a knockout mutant for important lipid synthesis genes key in the remodelling process (e.g. a putative phospholipase), the project will further explore the functioning of certain lipids.
Figure 1: Scheme of the hypothesised effect of nitrogen (N) limitation or nitrogen-phosphate (N/P) co-limitation on membrane lipids. (a) Under low nutrient availability the membrane composition is affected and the (b) lipid profile measurable using lipid chromatography-mass spectrometry systems changes. (c) Epifluorescence microscopy image of the diatom P. tricornutum and (d) transmitted light microscopy image of the prymnesiophyte G. huxleyi.
CENTA Flagship
This is a CENTA Flagship Project
Host
University of WarwickTheme
- Climate and Environmental Sustainability
- Organisms and Ecosystems
Supervisors
Project investigator
- Michaela Mausz (University of Warwick, [email protected])
Co-investigators
- Orkun Soyer (University of Warwick, [email protected])
- Katherine Helliwell (Marine Biological Association, [email protected])
How to apply
- Each host has a slightly different application process.
Find out how to apply for this studentship. - All applications must include the CENTA application form. Choose your application route
Methodology
This project focuses on cultivating several diatoms and prymnesiophytes under varying N or N/P concentrations to determine lipid composition, cell ecophysiology, changes in protein expression and structural changes in the cells.
Lipids will be identified and quantified using (high resolution) liquid chromatography-mass spectrometry (LC-MS). Ecophysiological approaches will cover photophysiology, pigments and nutrient uptake using a Phyto-PAM Phytoplankton Analyzer to measure parameters of photosynthetic performance, spectrophotometric measurements of chlorophyll and other pigments, and radioisotope assays for carbon fixation and nutrient uptake kinetics. In addition, motility will be characterised through fluorescent, time-lapse microscopy under different light regimes and on different substrates. Proteomic analysis will be conducted using in-house mass spectrometry facilities at Warwick and structural changes assessed by imaging flow cytometry, epifluorescence and transmission electron microscopy. Additionally, CRISPR-Cas9 mutation of lipid biosynthesis genes will allow a better insight into the involvement of lipids in adaptation to nutrient depletion.
Training and skills
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.
The student will receive training in a range of techniques in the supervisor’s and co-supervisors’ labs. This will include microbiological techniques from cultivation to cell quantification (flow cytometry), extraction of lipids and proteins, their measurement via lipidomics and proteomics, as well as bioinformatics tools data analysis, training in photophysiology measurements, usage of radioisotopes and gene knock-out experiments. Further, training in imaging techniques such as confocal laser scanning microscopy, transmission electron microscopy and imaging flow cytometry is available via staff at the Warwick Research Technology Platforms. CRISPR-Cas9 genetics are supported by Dr Helliwell.
Partners and collaboration
The supervisory team is composed of experts in their fields. Dr Mausz is a new group leader with an excellent track record in microalgae research and lipidomics. She aims to establish a motivated team to address essential topics related to ocean carbon fixation and climate change. Prof Soyer is an experienced researcher interested in cell metabolism and motility, who has supervised multiple successful projects, which resulted in high-impact publications. The student will also have the possibility to access resources from the MBA and collaborate with colleagues in the supervisors’ established networks.
Further details
Informal enquiries can be directed to Dr Michaela Mausz ([email protected]).
To apply to this project:
- You must include a CENTA studentship application form, downloadable from: CENTA Studentship Application Form 2025.
- You must include a CV with the names of at least two referees (preferably three) who can comment on your academic abilities.
- Please submit your application and complete the host institution application process via: https://warwick.ac.uk/fac/sci/lifesci/study/pgr/studentships/nerccenta/ University of Warwick projects will be added here: https://warwick.ac.uk/fac/sci/lifesci/study/pgr/studentships/nerccenta/studentships/ and application guidance is at the bottom of this page. Complete the online application form – selecting course code P-C1PB (Life Sciences PhD); from here you will be taken through to another screen where you can select your desired project. Please enter “NERC studentship” in the Finance section and add Nikki Glover, [email protected] as the scholarship contact. Please also complete the CENTA Studentship Application Form 2025 and submit via email to [email protected]. Please quote CENTA 2025-W14 when completing the application form.
Applications must be submitted by 23:59 GMT on Wednesday 8th January 2025.
Possible timeline
Year 1
Identification of lipids under N and N/P co-limitation and analysis of ecophysiological consequences of lipid changes in a few diatoms and prymnesiophytes.
Year 2
Further characterisation of ecophysiological consequences and mutation of a lipid synthesis gene in the diatom Phaeodactylum tricornutum.
Year 3
Proteomics, nutrient uptake and imaging of N and N/P co-limited microalgae.
Further reading
Abida H, Abida H, Dolch LJ, Meï C, Villanova V, Conte M, Block MA, Finazzi G, Bastien O, Tirichine L, Bowler C, Rébeillé F, Petroutsos D, Jouhet J, Maréchal E (2014) Membrane glycerolipid remodeling triggered by nitrogen and phosphorus starvation in Phaeodactylum tricornutum. Plant Physiol 167, 118-136.
Bondoc KGV, Heuchele J, Gillard J, Vyverman W, Pohnert G (2016) Selective silicate-directed motility of diatoms. Nat. Commun. 7: 10540. https://doi.org/10.1038/ncomms10540.
Guillonneau R, Murphy ARJ, Teng ZJ, Wang P, Zhang YZ, Scanlan DJ, Chen Y (2022) Trade-offs of lipid remodeling in a marine predator–prey interaction in response to phosphorus limitation. Proc Natl Acad Sci USA 119 (36), e2203057119
Moore CM, Mills MM, Arrigo KR, Berman-Frank I, Bopp L, Boyd PW, Galbraith ED, Geider RJ, Guieu C, Jaccard SL, Jickells TD, La Roch J, Lenton TM, Mahowald NM, Marañón E, Marinov I, Moore JK, Nakatsuka T, Oschlies A, Saito MA, Thingstad TF, Tsuda A, Ulloa O (2013) Processes and patterns of oceanic nutrient limitation. Nature Geosci. 6(9):701-710.
Stirrup R, Mausz MA, Silvano E, Murphy A, Guillonneau R, Quareshy M, Rihtman B, Aguilo Ferretjans M, He R, Todd JD, Chen F, Scanlan DJ, Chen Y (2023) Aminolipids elicit functional trade-offs between competitiveness and bacteriophage attachment in Ruegeria pomeroyi. ISME J. 17, 315-325.
Van Mooy BAS, Fredricks HF, Pedler BE, Dyhrman ST, Karl DM, Koblížek M, Lomas MW, Mincer TJ, Moore LR, Moutin T, Rappé MS, Webb EA (2009) Phytoplankton in the ocean use non-phosphorus lipids in response to phosphorus scarcity. Nature 458, 69-72.
Wetherbee R, Lind JL, Burke J, Qyatrano RS (2002) Minireview – the first kiss: establishment and control of initial adhesion by raphid diatoms. J. Phycol. 34:9-15.