Today I will talk about a seaweed with magnificent properties, able to adapt to high salinity and irradiance and, therefore, able to produce glycerol: Dunaliella salina.

What happens in the metabolism of this green alga when subjected to such conditions? It is observed that our alga, once transferred in a saturating solution of Salt, in about 90 minutes, begins to produce glycerol. This happens because Dunaliella salina is metabolically balanced with the osmolarity of the medium, thanks to a sterol-dependent sensor. This sensor will activate kinases, that will induce gene expression and so the production of proteins involved in the metabolism of glycerol.

Dunaliella salina also has the ability to change colour due to changes in environmental parameters (temperature, salinity and irradiance). If these parameters increase, it begins to generate lipid drops containing beta-carotene. Beta-carotene, being a carotenoid, is able to eliminate reactive oxygen compounds, dissipate excited triplets and above all, acts as a protective pigment in not entirely pleasant conditions. In short, Dunaliella salina will produce green chlorophyll under favorable conditions, otherwise it will produce beta-carotene and appear red. The extraordinary thing in the production of one or the other pigment is, that the 2 metabolic pathways that produce pigments, meet and somehow compete when there are limiting conditions.

But why does Dunaliella salina produce glycerol and not other compounds in these situations? Simple, starting from CO₂ the production of glycerol turns out to be energetically favorable.

In addition to having learned these notions, what I hope that remains is, the wonder. How is it possible that such simple organisms have these sophisticated adaptation mechanisms? How is it possible that the microalgae that are considered by most to be insignificant, despite being the basis of life, have the possibility of choosing the metabolic path on the base of the environmental conditions? We are not able to choose, at least as regards metabolism. Sometimes I think that we will never be up to those organisms that, even if without intellect, even without any animal features, can live always and in any case. The nature once again shows its greatness and does it with magnificent colours, and does so by colouring itself in red.

Maria Bruno