Phylogenetic trees for TrpG and TrpE sequences. archaeal and bacterial protein sequences were used to construct the unrooted tree. The last letter of the acronyms indicates the taxonomical position of the species. "E" marks Euryarchaeota, "C" Crenarchaeota, and "B" bacterial species. The two TrpE sequences of N. pharaonis are designated as _1E, _2E. For colour code and abbreviations, see legend of Figure 1.