Relative differences in gene expression between clades 8 and 2, as detected by microarrays and qRT-PCR.

a. E. coli O157:H7 Sakai chromosomal gene numbers [12].
b. Fold change differences between clade 8 (n = 12) and clade 2 (n = 12) strains; positive values were upregulated in clade 8.
c. mean ± standard deviation of relative fold change differences in gene expression between clade 8 (n = 6) and clade 2 (n = 6) strains; positive values were upregulated in clade 8.
d. mean reaction efficiencies of 12 O157:H7 strains.
e. qRT-PCR fold change in expression of the q antiterminator is based on clade 8 (n = 3) and 2 (n = 3) strains that carry only stx2 genes.