Gene content and organization of PR gene–containing genome segments from AND4 and BAA-1116.

PR (prd) and chromophore synthesis genes required for functional photoprotein are shown in red, transposase genes in blue. Yellow shading highlights a genomic region predicted by the program IslandPick to have originated from lateral gene transfer [38]. In accordance with the divergent ancestry of the prd gene and retinal biosynthesis genes compared to flanking genes (Table S1), the presence of a truncated transposase indicates that the genome region in AND4 containing prd has been modified by historical lateral gene transfer events.