Past inclusion of genetic material from bacteria, plants and animals has provided a group of microscopic algae with the potential to thrive and diversify according to a study published online on 15 October in the journal Nature. The study, benefiting from the collaboration of 77 experts from 11 countries, demonstrates how new traits can enter a lineage through the transfer of genetic material across very different organisms.

The research was based on the complete sequencing of the genome of Phaeodactylum tricornutum, a well studied species of diatom. Diatoms are a dominant and highly diverse group of aquatic microalgae that produce a staggering 20% of the oxygen in our atmosphere and convert the greenhouse gas carbon dioxide into organic matter through photosynthesis.

"Diatoms represent a veritable melting pot of traits - a hybrid of genetic mechanisms contributed by ancestral lineages of plants, animals and bacteria, and optimised over the relatively short evolutionary timeframe of 180 million years since they first appeared," says first author Chris Bowler of the French Ecole Normale Supérieure. "Our findings show that gene transfer between diatoms and other organisms has been extremely common, making diatoms 'transgenic by nature'," he adds.

The scientists compared the genome sequence of Phaeodactylum tricornutum (a pennate diatom) with that of the only other diatom whose genome sequence is known, Thalassiosira pseudonana (a centric diatom), and found an astonishing 40% difference.  This reveals an unusually rapid rate of gene diversification in this group, which is one reason for the high degree of diversity in diatoms. Differential gains and losses of genetic material, selective gene family expansions and mobilisation of transposable elements have been potent processes in delivering these evolutionary changes.

The UK contribution to this international research effort was provided by Michele Stanley from SAMS, who investigated carbohydrates, adhesive and cell wall genes, and by Colin Brownlee, director of the Marine Biological Association, who studied ion channel genes, particularly those involved in intracellular signaling.

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Note to editors

The research was funded through a number of projects. Diatom genome sequencing at the Joint Genome Institute (USA) was performed under the auspices of the US Department of Energy's Office of Science, Biological and Environmental Research Program, and by the University of California, Lawrence Berkeley National Laboratory, Lawrence Livermore National Laboratory and Los Alamos National Laboratory. P. tricornutum ESTs were generated at Genoscope (France). Funding for this work was also obtained from the EU FP6 Diatomics project (LSHG-CT-2004-512035), the EU-FP6 Marine Genomics Network of Excellence (GOCE-CT-2004-505403), an ATIP 'Blanche' grant from the CNRS (France) and the Agence Nationale de la Recherche (France).