Phytoplankton is acknowledged to be a very diverse source of bioactive molecules. These compounds play physiological roles that allow cells to deal with changes of the environmental constrains. For example, the diversity of light harvesting pigments allows efficient photosynthesis at different depths in the seawater column. Identically, lipid composition of cell membranes can vary according to environmental factors. This, together with the heterogenous evolutionary origin of taxa, makes the chemical diversity of phytoplankton compounds much larger than in terrestrial plants. This contribution is dedicated to pigments and lipids synthesized within or from plastids/photosynthetic membranes. It starts with a short review of cyanobacteria and microalgae phylogeny. Then the bioactivity of pigments and lipids (anti-oxidant, anti-inflammatory, anti-mutagenic, anti-cancer, anti-obesity, anti-allergic activities, and cardio- neuro-, hepato- and photoprotective effects), alone or in combination, is detailed. To increase the cellular production of bioactive compounds, specific culture conditions may be applied (e.g., high light intensity, nitrogen starvation). Regardless of the progress made in blue biotechnologies, the production of bioactive compounds is still limited. However, some examples of large scale production are given, and perspectives are suggested in the final section.

Background: Arbuscular mycorrhizal (AM) fungi, which engage a mutualistic symbiosis with the roots of most plant species, have received much attention for their ability to alleviate heavy metal stress in plants, including cadmium (Cd). While the molecular bases of Cd tolerance displayed by mycorrhizal plants have been extensively analysed in roots, very little is known regarding the mechanisms by which legume aboveground organs can escape metal toxicity upon AM symbiosis. As a model system to address this question, we used Glomus irregulare-colonised Medicago truncatula plants, which were previously shown to accumulate and tolerate heavy metal in their shoots when grown in a substrate spiked with 2 mg Cd kg^-1. Results: The measurement of three indicators for metal phytoextraction showed that shoots of mycorrhizal M. truncatula plants have a capacity for extracting Cd that is not related to an increase in root-to-shoot translocation rate, but to a high level of allocation plasticity. When analysing the photosynthetic performance in metal-treated mycorrhizal plants relative to those only Cd-supplied, it turned out that the presence of G. irregulare partially alleviated the negative effects of Cd on photosynthesis. To test the mechanisms by which shoots of Cd-treated mycorrhizal plants avoid metal toxicity, we performed a 2-DE/MALDI/TOF-based comparative proteomic analysis of the M. truncatula shoot responses upon mycorrhization and Cd exposure. Whereas the metal-responsive shoot proteins currently identified in non-mycorrhizal M. truncatula indicated that Cd impaired CO₂ assimilation, the mycorrhiza-responsive shoot proteome was characterised by an increase in photosynthesis-related proteins coupled to a reduction in glugoneogenesis/glycolysis and antioxidant processes. By contrast, Cd was found to trigger the opposite response coupled the up-accumulation of molecular chaperones in shoot of mycorrhizal plants relative to those metal-free. Conclusion: Besides drawing a first picture of shoot proteome modifications upon AM symbiosis and/or heavy metal stress in legume plants, the current work argues for allocation plasticity as the main driving force for Cd extraction in aboveground tissues of M. truncatula upon mycorrhization. Additionally, according to the retrieved proteomic data, we propose that shoots of mycorrhizal legume plants escape Cd toxicity through a metabolic shift implying the glycolysis-mediated mobilization of defence mechanisms at the expense of the photosynthesis-dependent symbiotic sucrose sink.

Biosorption, the naturally occurring physiochemical process which passively concentrates and binds contaminants to cellular structures, can be used in biological systems for the removal of metal ions from polluted waters. It also has the potential to achieve better performance at lower cost than conventional wastewater treatment technologies. The aim of this study was to characterize the ability of the freshwater diatom Planothidium lanceolatum (Brébisson) Lange-Bertalot to biosorb cadmium (Cd), copper (Cu) and zinc (Zn) from aqueous solutions. This diatom is one of the most dominant microalgae in the Tensift River, Marrakech region, Morocco, into which industrial wastewaters are often discharged directly, without pretreatment. As the water from this river is used for irrigation, it represents a potential risk to the environment and human health. The choice of these three heavy metals is based on their high concentrations in mining waste and industrial wastewaters. Our results indicate that the biosorption of metals by P. lanceolatum increased with the initial concentration of metal ions in the medium up to 100–130 mg L⁻¹. The maximum biosorbed metal ion concentrations were 104, 81 and 41 mg per 16×10⁸ diatom cells L⁻¹ for Zn, Cu and Cd, respectively. The maximum uptake of metals was obtained at pH 6.0 for Cu and at pH 8.0 for Cd and Zn. An increase in the biosorption of P. lanceolatum was observed with an increase in temperature from 15 to 25†C. The biosorption of all three metal ions followed the Langmuir isotherm. Competitive biosorption of Cd, Cu and Zn ions was also achieved. Fourier transform infrared spectroscopy revealed the different metal-binding functional groups on the diatom surface that are able to react with metals in the medium. The results suggest that P. lanceolatum can be used as a biosorbent for the efficient removal of heavy metals from aqueous solutions at temperature and pH values close to average values in the Tensift River.