Phylogenetic tree of TrpEb sequences. Cdi_2 is encoded by a paralog copy of trpEb_1 that has been inserted ahead of the Cdi trp operon. TrpEb_2 is encoded by a highly divergent paralog subclass of trpEb that probably has a specialized function . No TrpEb_2 sequences were used to construct concatenates (Fig. 2). Rsp_2 is shown with two patterns, indicating uncertainty about whether it is an ancient paralog or a xenolog.