Joint Doctoral Degree : France (UPMC) / Australia (UNSW)
PhD under a cotutelle agreement
PhD under a Cotutelle Agreement - world-class student experience
I undertook my PhD under a cotutelle agreement between UPMC (Paris) and the University of New South Wales (Sydney), funded by a competitive Bourse Ministérielle from the French government. A cotutelle means joint supervision and enrolment across two universities in two countries — in practice, double the paperwork, but also modules in Paris, lab work spanning Banyuls, Paris, Grenoble and Sydney, and conferences in Luxembourg and Bath.
Despite the logistics, I published six papers (five as first author) during my 3.5-year studentship (all without AI!) and graduated with a double diploma. The experience built exceptional organisational skills and independence — skills I later put to use as a Lecturer at the University of Stirling, where I set up the university's own UK/France/Belgium cotutelle partnership and supervised its first two PhD students, Augustin Geron and Clement Lozano, alongside colleagues Pr. Ruddy Wattiez and Pr. Philippe Lebaron.
Title:
Physiological and molecular responses of the marine oligotrophic ultramicrobacterium Sphingopyxis Alaskensis rb2256 to visible light and ultraviolet radiation
PhD in Marine Microbiology
Abstract
Ultraviolet radiation reaching the Earth’s surface (UVR, 280-400 nm) may penetrate deep into the clear oligotrophic waters influencing a large part of the euphotic layer. Marine heterotrophic bacteria at the surface of the oceans are especially sensitive to the damaging solar radiation due to their haploid genome with little or no functional redundancy and lack of protective pigmentation. In a context of climate change and ozone depletion, it is clearly important to understand the physiology and underlying molecular UVR responses of abundant marine bacteria species. We chose the marine ultramicrobacterium Sphingopyxis alaskensis as a reference species to study the impact of solar radiation due to its numerical abundance in oligotrophic waters and its photoresistance, previously reported. For this purpose, we focused on the formation of the two major UVB-induced DNA photoproducts (CPDs and 6-4PPs) as well as the differential protein expression under solar radiation. We first demonstrated that the GC content of prokaryotic genome had a major effect on the formation of UVB-induced photoproducts, quantified by HPLC-MS/MS. Due to its high GC content, S. alaskensis presented a favoured formation of highly mutagenic cytosine-containing photoproducts and therefore would be more susceptible to UVinduced mutagenesis. By comparing S. alaskensis to another marine bacterium Photobacterium angustum, we observed for the latter strain a remarkable resistance to high UVB doses associated with a decrease in the rate of formation of CPDs explained by a non-conventional activity of photolyase. We also demonstrated that DNA damage in S. alaskensis was markedly modulated by growth temperature and time spent in stationary phase. In order to assess the effects that environmental UV-R had on regulatory networks and pathways of S. alaskensis, and determine how the cell’s physiology was affected, a quantitative proteomics investigation was performed. Changes in proteome were analyzed, with the recent and powerful mass spectrometry based approach using iTRAQ methodology. Approximately, one third of the proteome of S. alaskensis was identified, with 119 statistically and significantly differentially abundant proteins. Cellular processes, pathways and interaction networks were determined and gave us unique insight into the biology of UV response and adaptation of S. alaskensis.