The oceans of our
planet are Earth’s largest ecosystem. About 50% of the primary
productivity is attributable to them. The most important
photosynthetic eukaryotes are the diatoms; they contribute about 40%
of the primary marine production, and thus produce almost 1/4 of the
oxygen we breathe. Although they form only a small part of the
photosynthetic biomass, in some regions of the ocean, they can fix the
same amount of carbon per day as a forest of terrestrial plants.
There are at least 100,000 species of diatoms, which makes them the most abundant photosynthetic group after the angiosperms. Diatoms, therefore occupy a central position in the control of marine resources, and for prediction of climatic change. However, we possess very little knowledge about the biology of diatoms today. Furthermore, algal blooms are often caused by diatoms, sometimes with production of toxins (a cause of anmesiac intoxication by shellfish), and they may have harmful effects on the local ecosystem, fishing, aquaculture and tourism. Finally, diatoms are the principal cause of “biofouling”, because of their capacity to adhere to surfaces and to produce extracellular polymeric mucilaginous substances (EPS). The total direct costs of “antifouling” treatments in the world is estimated at 3 billion dollars.
In parallel to their ecology, the diatoms are also interesting for the study of evolution, because their genomes are the result of a fusion of 3 genomes derived from their cyanobacterial and eukaryotic ancestors. Furthermore, they have applications in biotechnology: in nanotechnology because of their silica, as a nutrient in aquaculture and as biofactors for the production of molecules such as omega-3 type fatty acids.
Information on gene expression in response to environmental signals, associated with EST sequence alignments between the genomes of the two diatoms, T. pseudonana and P. tricornutum, will provide basic knowledge for the study of important questions in diatom biology, for example :
Furthermore, a knowledge of the genes of Phaeodactylum tricornutum will facilitate the utilization of this organism as a potential cell for the expression of genes from other brown algae, which may be interesting for industry.