Genome sequence of Crocosphaera watsonii strain WH0402. Crocosphaera watsonii WH 0402

This genome is part of a comparative genomic study of six strains of Crocosphaera watsonii - a biogeochemically important nitrogen-fixing marine cyanobacterium. Four genomes were sequenced for the study and two had been previously sequenced. The six strains are a single species but fall into two phenotypic groups, three large-cell types and three small-cell types, with ecosystem implications for some of the phenotypic differences. For example, the large-cell types produce up to 10 times the amount of extracellular polysaccharides (EPS) as the small cell-strains, indicating that their contribution to marine carbon cycling is much larger than the small-cell types. In previous work, DNA sequences for genetic markers were identical for all strains, despite the known phenotypic differences. In this study, whole-genome comparisons were used to identify the genetic basis for observed differences between strains. The strain of this project, WH0402, is a large-cell strain.