Fig 1.

Maximum likelihood phylogenetic tree of all 100 mrkD sequences, grouped into three distinctive clades (red boxes). The ancestral node of each clade is denoted by a blue circle. IA565 represents the plasmid variant of mrkD. For each allelic variant, the information includes the name of a representative isolate followed by the total number of isolates carrying the allele (preceded by “n”). The stars indicate that the allelic variant is represented by (at least) one E. coli isolate.