Nine Le Reun
Thesis title: Elucidating chemicals exchange between Thalassiosira and bacteria interactions.
Supervisors: Professor Justin Seymour, Jean-Baptiste Raina, Anna Bramucci and Penelope Ajani.
Phytoplankton are photosynthetic microorganisms, which contribute to half of marine net primary production and constitute the base of the oceanic food web. Approximately half of the molecules derived from phytoplankton primary production are consumed directly by heterotrophic marine bacteria, which are responsible for important biogeochemical transformations and represent the largest fraction of the ocean biomass.
Together, these groups of microbes play a central role in the major ocean biogeochemical cycles (e.g. carbon, nitrogen, and sulfur), which control marine ecosystem productivity and influence climate. In recent years, it has become apparent that intimate ecological interactions, spanning mutualism to parasitism, occur between these two groups (Amin et al., 2015; Durham et al., 2015; Van Tol et al., 2017). Such associations involve complex chemicals exchanges and communication, such as micronutrient exchanges (e.g. iron) and growth-promoting molecules (e.g. indole-acetic acid). However, our understanding of the onset, chemical exchanges, and molecular pathways regulating phytoplankton-bacteria symbioses is still limited.
In the proposed project, I aim to investigate the interactions between the diatoms Thalassiosira and bacteria by combining a multi-disciplinary approach including transcriptomics, metabolomics, co-growth and single-cell imaging techniques to determine the mechanisms underpinning these pelagic symbioses. Results derived from this work will help to better understand the importance of these interactions for marine ecosystems function, biogeochemical cycling and ultimately the climate.