Phylogenetic tree of TrpB sequences. Det_2 is diagrammed with both patterns, indicating it could be either an ancient paralog or a xenolog. Sco_CDA is a specialized-pathway paralog (antibiotic). Asp, Asp_2, Npu, and Npu_2 are paralogs from a gene duplication that preceded speciation of Npu and Asp. The Asp and Npu sequences were arbitrarily used for input into the concatenate tree of Fig. 2. TCG-7 is fragmented. TCG-1 contains xenolog members of whole-pathway operons from H. pylori, C. diptheriae, and C. glutamicum. Asterisks (Tma, Cje, and Eco) indicate domains existing as part of TrpAb•TrpB fusions.