Fig. 2.
Comparisons of gene compliment between A. anophagefferens and other co-occurring phytoplankton species. Aa, A. anophagefferens; Pt, P. tricornutum; Tp, T. pseudonana; Ot, O. tauri; Ol, O. lucimarinus; S1, Synechococcus clone CC9311; S2, Synechococcus clone CC9902. (A) The number of light-harvesting complex (LHC) genes present in each phytoplankton genome (red bars; left axis) and Imax, the irradiance level required to achieve maximal growth rates in each phytoplankton (black squares; right axis) are shown. Among these species, A. anophagefferens possesses the greatest number of LHC genes, achieves a maximal growth rate at the lowest level of light, and blooms when light levels are low. (B) The number of genes associated with the degradation of nitriles, asparagine, and urea in each phytoplankton genome. A. anophagefferens grows efficiently on organic nitrogen and possesses more nitrilase, asparaginase, and urease genes than other phytoplankton. (C) Interspecies comparison of the genes encoding proteins that contain the metals Se, Cu, Mo, Ni, and Co (left axis) and Semax, the selenium level (added as selenite shown as log concentrations) required to achieve maximal growth rates in A. anophagefferens, P. tricornutum, T. pseudonana, and Synechococcus (white circles; right axis). The range of dissolved selenium concentrations found in estuaries is depicted as a yellow bar on the right y axis. A. anophagefferens has the largest number of proteins containing Se, Cu, Mo, and Ni and blooms exclusively in shallow estuaries where inventories of these metals are high. SI Appendix contains details of irradiance- and Se-dependent growth data and Se concentrations in estuaries.