The scientists have sequenced and analysed the genome of the diatom Phaeodactylum tricornutum. Their results were recently published in the scientific journal Nature (“The Phaeodactylum genome reveals the evolutionary history of diatom genomes“, Nature online, October 15th 2008). The large scientific project, coordinated by Dr. Chris Bowler at the CNRS in Paris, was made possible through the close cooperation of 77 scientists at 31 different institutes in 11 countries. The German participants in the sequencing project included molecular biologists from the Alfred Wegener Institute for Polar and Marine Research in Bremerhaven, the Leibniz Institute for Marine Sciences in Kiel and the University of Constance.

Microalgae, which belong to the phytoplankton, are the basis of the marine food chain. Probably the most important group, the diatoms, are responsible for 40 per cent of marine photosynthesis (marine carbon dioxide fixation), which is approximately 20 per cent of the global carbon dioxide fixation. Therefore, diatoms, have an important function in the earth’s carbon dioxide balance. Diatom cells are more complicated than those of land plants because they are, in genetic and cell biological terms, a symbiosis of several cell types. During evolution, a eukaryotic alga was integrated into another eukaryotic cell and converted into a cell organelle.

The researchers were surprised to discover not only genes of the former endosymbiont and the host cell, but also hundreds of bacterial genes. Although the transfer of bacterial genes into eukaryotes is generally regarded as a rare event, it seems that gene transfer is far more common in diatoms. This leads to an unusual mixture of genes in diatoms that play an important role in managing nutrients (organic carbon and nitrogen) and detecting environmental changes.

The researchers from Constance, led by Prof. Peter Kroth and Dr. Ansgar Gruber, focused mainly on the spatial distribution of the metabolic pathways in the diatom cells. They found that the distribution of some metabolic pathways differs from the cells of land-based plants. This might explain why, in contrast to terrestrial plants, diatoms are particularly effective in converting carbon dioxide (CO2) into biomass.

Source: University of Constance - 16 Oct. 2008 (mst - 22 Oct. 2008) (P)

Further information:
University of Constance
Faculty of Biology
Prof. Dr. Peter Kroth
Tel.: +49 (0)7531 88 4816