DIATOM GENOMICS: IMPORTANT CONSIDERATIONS FOR GENOME SEQUENCING OF ECOLOGICALLY RELEVANT ORGANISMS

Armbrust, E. V. School of Oceanography, University of Washington, Seattle, WA 98195 USA Diatoms are one of the most abundant groups of aquatic eukaryotic microorganisms found in nature, with a wide distribution in marine and freshwater habitats. These unicellular organisms are responsible for a huge proportion of global primary productivity – in fact, Mann (Phycological Rev. 38:437) recently suggested that diatoms are responsible for more carbon fixation than all the world's rain forests. Furthermore, because of their dominance under high nitrate conditions and their enhanced sinking rates due either to aggregation and/or packaging into fecal pellets, diatoms play a critical role in the biological pump that mediates carbon and nitrogen fluxes out of euphotic zones and into deeper waters. Due to their important role in carbon sequestration, the Department of Energy's Microbial Genome Program is initiating a diatom whole genome‐sequencing project. An update on the status of this project will be provided and some of the stumbling blocks encountered in the early stages of the project will be discussed. In addition, important considerations for choosing ecologically relevant organisms for genome studies, such as the ability to perform genetic manipulations, will be highlighted. An emerging theme in the genome information accumulated thus far from a variety of organisms is that large numbers of putative genes have unknown functions. Sequence data alone is not enough to discern all the attributes of an organism – mutational analyses of genes are also critical. Since diatoms are diploid, sexual reproduction is an obligate step in mutant generation. Examples of what is known about diatom sexual cycles will be provided.