Mechanistic impact of Gracilaria bailinae extracts on photosynthesis and metabolism in Phaeodactylum tricornutum.

In the intricate realm of aquatic ecosystems, biotic interactions play pivotal roles in shaping the physiological responses and survival strategies of microorganisms. This study investigates the effects of Gracilaria bailinae on photosynthesis and metabolism on the diatom Phaeodactylum tricornutum and the ecological significance. Our results reveal considerable suppression by G. bailinae on both its light-dependent and light-independent reactions of photosynthesis in P. tricornutum. A pronounced decline in carbon fixation was observed causing. the diatom to prioritize its carbon flux towards carbohydrate synthesis for its cellular energy needs. At high G. bailinae concentrations a marked reduction in lipid content indicated their importance as emergency energy sources. This response in lipid mobilization under photosynthetic stress is an evolutionary strategy for environmental adaptation. In addition, G. bailinae-induced stress amplified lysosomal activity in the diatom. Such an upsurge in oxidative stress appears to fast-track cellular death. We conclude that the ROS production, induced by G. bailinae, acts as a linchpin in mediating stress responses, thereby significantly reconfiguring the metabolism in the diatom. This study not only elucidates the physiological countermeasures of microalgae against biotic stressors but it also underscores the complex interactions between aquatic microorganisms.