Specific light-regime adaptations, terpenoid profiles and engineering potential in ecologically diverse Phaeodactylum tricornutum strains

Microalgae, and among them, the diatom Phaeodactylum tricornutum stand out with their remarkable versatility and metabolic engineering potential. Diatoms exhibit substantial variability in metabolism, photosynthetic physiology and environmental adaptation, even across the same species. These factors can affect the design and outcome of metabolic engineering strategies. In this study, we profiled the diversity of biotechnologically relevant traits of three P. tricornutum strains (Pt1, Pt6, and Pt9) under different light regimes to identify the most suitable chassis to be employed as bio-factory to produce high-value terpenoids. We conducted detailed assessments of these strains, using pulse amplitude modulated (PAM) fluorometry to measure photosynthetic efficiency and we analyzed the composition of pigments and triterpenoids, as main terpenoid metabolic sinks. Parameters such as the maximum quantum yield of PSII (Fv/Fm), the efficiency of excitation energy capture (Fv/Fm), and OJIP kinetics were used to estimate photosynthetic performance in different light regimes. Additionally, we evaluated their transformation efficiency and their capacity to produce heterologous monoterpenoids, using geraniol as a model product. Our findings revealed that Pt1, widely used in laboratories, exhibits robust growth and photosynthetic performance under standard laboratory conditions. Pt6, adapted to intertidal environments, shows unique resilience in fluctuating conditions, while Pt9, with its high-temperature tolerance, excels under continuous high irradiance. Additionally, this variability across strains and light conditions influenced the metabolic output of each strain. We concluded that understanding the physiological responses of different P. tricornutum strains to light is crucial for optimizing their use in metabolic engineering. The insights gained from this research will facilitate the strategic selection and exploitation of these strains in algae biotechnology, enhancing the production of commercially valuable compounds such as high-value terpenoids and derivatives. This comprehensive characterization of strains under varying light conditions offers a pathway to more efficient and targeted metabolic engineering applications. HighlightsO_LIPt1, Pt6, and Pt9 exhibit distinct physiology under different light regimes. C_LIO_LIPt9 is photosynthetically more performant in continuous light, Pt6 in photoperiod. C_LIO_LILight regimes affect pigments and triterpenoid content in all three strains. C_LIO_LIEach strain exhibits a specific carotenoid and triterpenoid composition. C_LIO_LIBacterial conjugation of episomes varies across strains, it is more efficient in Pt1. C_LIO_LIPt1 is suited for the heterologous synthesis of monoterpenes (geraniol). C_LI