Schematic portrayal of two whole-pathway trp operon transfers and two partial-pathway trp operon transfers. The partial tree shown is taken from Fig. 1, which identifies the organisms. In C. diptheriae, the vertical evolutionary events of gene duplication and insertion that occurred following LGT can be visualized by comparing the gene organization shown to the right (including intergenic spacing) with the gene organization originally received from the enteric donor (bottom right). Gene insertions that followed LGT are shown in white.