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Light is a driving force behind the synthesis of biomass in photoautotrophs. In pelagic ecosystems, highly variable light strongly affects microalgae at an ecological (success and succession), molecular (acclimation, carbon allocation), photosynthetic and growth levels. Therefore, manipulation of light appears to be an attractive tool for enhancing growth of microalgae in order to extend the use of these organisms in biotechnological field. In this study, we investigate the responses of the diatom alga Skeletenoma marinoi to different growth light regimes, that induced composite acclimative patterns manifesting in strong alterations in the cell biology. Although the growth rate is dependent upon the integrated daily light dose received by the algae, we demonstrate that physiological and biochemical acclimation responds to additional light stimuli. The application of fluctuating red light on a sinusoidal blue light spectral distribution induces an increase in non-photochemical quenching and the de-epoxidation state of the xanthophyll cycle along with modifications of the metabolic state of the cells, e.g. an increase in carbohydrates, glycolipids and saturated fatty acids. Providing an unnatural square-wave light course induces drastic changes in photosynthesis, pigment and macromolecular composition of the cells. [ABSTRACT FROM AUTHOR]

Photochemoprevention can be a valuable approach to counteract the damaging effects of environmental stressors (e.g., UV radiations) on the skin. Pigments are bioactive molecules, greatly attractive for biotechnological purposes, and with promising applications for human health. In this context, marine microalgae are a valuable alternative and eco-sustainable source of pigments that still need to be taken advantage of. In this study, a comparative in vitro photochemopreventive effects of twenty marine pigments on carcinogenic melanoma model cell B16F0 from UV-induced injury was setup. Pigment modulation of the intracellular reactive oxygen species (ROS) concentration and extracellular release of nitric oxide (NO) was investigated. At the cell signaling level, interleukin 1-β (IL-1β) and matrix metallopeptidase 9 protein (MMP-9) protein expression was examined. These processes are known to be involved in the signaling pathway, from UV stress to cancer induction. Diatoxanthin resulted the best performing pigment in lowering MMP-9 levels and was able to strongly lower IL-1β. This study highlights the pronounced bioactivity of the exclusively aquatic carotenoid diatoxanthin, among the others. It is suggested increasing research efforts on this molecule, emphasizing that a deeper integration of plant ecophysiological studies into a biotechnological context could improve the exploration and exploitation of bioactive natural products. [ABSTRACT FROM AUTHOR]