Insights into the evolution of cellular and regulatory processes in mixoplankton

Mixoplankton are key organisms in marine ecosystems, due to their ability to combine the two nutrition strategies of phototrophy and phagotrophy. Their dual mode of nutrition has major impact on trophic food webs and general biogeochemical cycles. Processes that are related to phagotrophy and phototrophy include the production of toxins for subsequent prey lysis and uptake, and the ability to sequester plastids (kleptoplasts) from photosynthetic prey. The studies presented in this thesis aim to (i) explore the processes of phagotrophy and phototrophy in marine protists in an evolutionary context, (ii) to extend our knowledge on the underlying mechanisms of toxin biosynthesis in the mixoplanktonic species Prymnesium parvum, (iii) to investigate the physiology and driving factors of phagotrophy in P. parvum under different treatments, (iv) to elucidate the molecular mechanisms involved in functionality of kleptoplasts in the ciliate Strombidium cf. basimorphum.