Figure 4.

Evolutionary relationships of the O26:H11 strains based on the concatenated ORFs of the eight cas genes. (A) Schematic representation of the type I-E CRISPR-Cas system. The cas genes are drawn to scale. (B) Maximum Likelihood tree based on the concatenated ORFs of the eight cas genes. The evolutionary history was inferred by using the Maximum Likelihood method based on the Jukes-Cantor model. The bootstrap consensus tree inferred from 100 replicates is displayed. Branches corresponding to partitions reproduced in <50% bootstrap replicates are collapsed. The percentage of replicate trees in which the associated taxa clustered together in the bootstrap test (100 replicates) is shown next to the branches. Initial tree(s) for the heuristic search were obtained automatically by applying Neighbor-Join and BioNJ algorithms to a matrix of pairwise distances estimated using the Maximum Composite Likelihood (MCL) approach, and then selecting the topology with superior log likelihood value. All positions containing gaps and missing data were eliminated. There were a total of 8421 positions in the final dataset. Evolutionary analyses were conducted in MEGA6. Isolates DEC9A, DEC9E, and DEC10D were not included in the analysis due to the presence of frameshifts.