FIG 3 .

Point mutations in genes encoding components of the phosphoenolpyruvate-carbohydrate phosphotransfer system (PTS) are the most frequent in evolved ΔccrM clones. (A) A simplified model for the PTS in C. crescentus based on homology searches (24, 47) and on the experimental work done on the Rhizobiales members Brucella melitensis and Sinorhizobium meliloti (36, 41, 48). The PTS allows a phosphate group to be transferred from phosphoenolpyruvate (PEP) to specific carbohydrates via several protein intermediates—EI^Ntr, HPr, and EII—to regulate their import into the cytoplasm. EI^Ntr and HPr may have additional regulatory functions via unidentified factors in Alphaproteobacteria. (B) Amino acid changes (counts) caused by point mutations found in the coding sequence of ptsP (EI^Ntr) in 12 clones isolated at generation 300 (blue, whole-genome sequencing) or at generation 50 (red, targeted PCR and Sanger sequencing). (C) Amino acid changes (counts) caused by point mutations found in the coding sequence of hprK (HprK) in 12 clones isolated at generation 300 (blue, whole-genome sequencing) or at generation 50 (red, targeted PCR and Sanger sequencing).