Synechococcus Metagenomes from Scripps Institute Pier. marine metagenome

Six seawater samples were taken at 2 monthly intervals over the course of year from the end of the Scripps Institute of Oceanography pier. These samples were treated with flow cytometry to enrich for Synechococcal species (select on the basis of fluorescence of photosynthetic pigments). The metagenomes obtained allow the elucidation of both the composition of each individual metagenome, and seasonal fluctuation in the Synechococcal population. Synechococcus are oxygenic photoautotrophic cyanobacteria found throughout the world's oceans. Due to their photosynthetic lifestyle and sheer abundance, they are significant participants in oceanic primary production and the global carbon cycle (Johnson and Sieburth, 1979; Waterbury et al., 1979; Glover, 1985; Li, 1994) (Richardson and Jackson, 2007). There is a strong foundation of genetic information describing the diversity of marine Synechococcus. They are a closely related group of microorganisms sharing greater than 95% of their 16S rRNA gene sequences (Urbach et al., 1998; Fuller et al., 2003) and multiple genomes of these organisms are now available, for example (Palenik et al., 2003; Palenik et al., 2006). Within this group, multiple clades have been identified (Ferris and Palenik, 1998; Rocap et al., 2002; Fuller et al., 2003), some with distinct physiological capabilities (Toledo et al., 1999). Surprisingly up to 15% of the genes in some Synechococcus strain genomes carry characteristic signatures of horizontal gene transfer and are reminiscent of pathogenicity islands (Palenik et al., 2003; Palenik et al., 2006). A comprehensive analysis of this has now been done for available Synechococcus genomes ( Dufresne et al., 2008). Using high speed flow cytometric sorting based on its phycoerythrin fluorescence to greatly enrich for Synechococcus, we obtained cells and subsequently metagenome data from a natural population. This revealed for the first time the extent of Synechococcus diversity in a natural population relative to cultured isolates from the same environment and the role of horizontal gene transfer and plasmids in shaping this diversity.