FIG. 1.

Phylogenetic relationships of mutS alleles from 72 ECOR strains. The tree shown represents the strict consensus of eight equally parsimonious trees and has a tree length of 283 steps. Most parsimonious trees had a CI of 0.48 and an RI of 0.83. Measures of clade confidence are reported in italics below each node in the form of bootstrap values. The internal brackets to the right of each clade reflect monophyletic strain groupings with respect to the E. coli MLEE lineages A, B1, B2, D, and E. Broken internal brackets indicate groups of strains that formed polytomies on the tree and that are ambiguous with respect to strain polyphyly. The larger external brackets designate the four distinct clades derived from mutS sequences (denoted by roman numerals I to IV). Individual branch lengths are presented above each branch; the numbers of unambiguous substitutions that mapped to the tree only once are given in parentheses.