Figure 1. Evolutionary analyses of Paulinella ovalis-like SAGs.

(a) Light microscopy image of the photosynthetic Paulinella chromatophora (left) and its phagotrophic sister P. ovalis (right). (b) RAxML⁴⁸ tree (GTR + Γ + I model) inferred from 18S rDNA showing the phylogenetic position of P. ovalis-like cells within Rhizaria. Single-cell sorting identified several P. ovalis-like cells that comprise two distinct heterotrophic Paulinella clades (Clade 1 and Clade 2) of which Clade 1 is most closely related to the photosynthetic P. chromatophora and Paulinella sp. FK01¹⁴, and is the subject of our study. RAxML and PhyML⁴⁹ bootstrap values are shown above and below the branches, respectively (only those ≥ 60% are shown). The unit of branch length is the number of substitutions per site. The GenBank accession numbers (where available) are shown after each taxon name. (c) Taxonomic distribution of unique BLASTx hits (e-value ≤10⁻¹⁰) using the contigs from the six P. ovalis-like single cell SAGs for which we have 454 data. The percentage distribution of each phylum across all six SAGs is shown. The arrows indicate markedly different phyletic origins of DNA among the SAGs.