Codon Usage Bias in Phytoplankton

Non-random usage of synonymous codons, known as “codon bias”, has been described in many organisms, from bacteria to Drosophila, but little is about it phytoplankton. This phenomenon thought be driven by selection for translational efficiency. As the efficacy proportional effective population size, species with large sizes, such phytoplankton, are expected have strong codon bias. To test this, we measured bias 215 strains Haptophyta, Chlorophyta, Ochrophyta (except diatoms that were studied previously), Dinophyta, Cryptophyta, Ciliophora, unicellular Rhodophyta and Chlorarachniophyta. Codon modest most groups, despite astronomically sizes marine The strength bias, number strongest Haptophyta weakest optimal codons GC-ending cases, several shifts AT-ending observed (mainly Ciliophora). takes a long time reach new equilibrium after shifts, having show lower frequency compared other species. Genetic diversity, calculated more than three sequenced, modest, indicating orders magnitude census which helps explain study represents first comparative analysis across multiple major phytoplankton groups.