Distribution of T2SS
in non-pathogenic E. coli strains. Phylogeny is from Archer et al. , with O157:H7 as an outgroup lacking both T2SSα and T2SSβ. Loci encoding the two T2SS types (where present) are diagrammed for each strain. Branch lengths are arbitrary. T2SSαgsp genes are colored yellow, and T2SSβgsp genes are shown in red.