Marine primary production is mainly driven by microscopic phytoplankton since phototrophic picocyanobacteria and picoeukaryotes contribute to almost all photosynthesis that takes place in the vast photic zones of the oligotrophic open ocean. Picocyanobacteria, green algae, diatoms and prymnesiophytes are the numerically most abundant primary producers on Earth and the abundance of some of them is predicted to increase due to climate change. Marine planktonic microorganisms generally show stable cell numbers, with growth and loss largely balanced. Ultimately, all primary production will be converted into particulate or dissolved organic matter (DOM) which becomes the main source of carbon and energy for the complex marine food web (mainly, heterotrophic bacteria). DOM is thought to be generated by cell death, viral lysis and inefficient grazing, but also living organisms are known to be, per se, inevitably or ‘intentionally’ leaky, e.g. through the production of extracellular vesicles, active efflux processes or, simply, permeable membrane leakage. In this sense, phytoplankton drive bacterial community dynamics as they are the main suppliers of organic matter. We recently observed that nutrient exchange plays a key role in phototroph-heterotroph interactions and current work in the group has shown that different phytoplankton species generate a variety of metabolites that condition the response and behaviour of their co-occurring heterotrophic bacteria. Hence, this project aims to dissect the key metabolites produced in these systems and determine how these exert an influence other species.

Figure 1: Interactions observed between Synechococcus and Ruegeria pomeroyi. Modified from Christie-Oleza et al 2017 Nature Microbiology.


The prospective student will have access to the unique culture collection in the Christie-Oleza lab. Cultures will be grown in defined combinations of synthetic communities and growth monitored by flow cytometry. Metabolites will be identified via targeted and non-targeted LC-MS. Community responses to interactions will be assessed by high-throughput proteomics. Heterotrophic bacteria are capable of degrading a wide range of key relevant metabolites produced by marine phytoplankton and, hence, knock-out mutants in these catabolic pathways will be generated in order to monitor the effect on the interaction. This PhD project will offer a unique opportunity for the student to learn state-of-the-art techniques and full access to all available facilities (i.e. mass spectrometry platform and synthetic biology facilities). Other techniques such as routine microbiology and molecular biology techniques will also be used on a day-to-day basis.

Training and Skills

This exciting project will be held at the University of Warwick which offers a friendly, young and dynamic environment with a strong intellectual background in molecular environmental science. Supervisors will offer the prospective student training within our multidisciplinary world-class research facilities.

CENTA students are required to complete 45 days training throughout their PhD including a 10 day placement. In the first year, students will be trained as a single cohort on environmental science, research methods and core skills. Throughout the PhD, training will progress from core skills sets to master classes specific to CENTA research themes. 


Year 1: Set up culture and monitor growth under different combinations. Set-up mass spectrometry methods to analyse the metabolites present in collected culture supernatants.

Year 2: Generate knockout mutants in key metabolic pathways and monitor the effect on their interaction. Evaluate the proteomic response of different microbes (and knockout mutants) when exposed to different key metabolites identified.   

Year 3: The student will embark on fieldwork to sample seawater from relevant (well-defined) coastal locations (e.g. Mallorca coast) and run incubations of these metabolites with natural marine communities in collaboration with the spanish marine research station.

Partners and collaboration (including CASE)

This project has a high potential in becoming CASE, building collaborations within industries which explore and use metabolites in their products.


Further Details

Potential applicants are invited to contact Joseph Christie-Oleza (j.christie-oleza@warwick.ac.uk) for more details and to express an interest in the project.