Table I.

Strains used in this study.

Strain	Description	Source or reference
TEA028	Derivative of EHEC serotype O157:H7 strain EDL933, ΔgalETKM::tetA	Ho and Waldor (2007)
TEA028-rne	Derivative of TEA028 into which the IPTG-inducible, HA- and His6-tagged rne gene from E. coli RNE102 has been transduced. This strain also produces the LacIQ repressor from a plasmid	This study
EDL933 ΔgalU	Derivative of EDL933 in which a kanamycin resistance marker has been inserted into the galU gene	This study
EDL933ΔLEE	Derivative of EDL933 in which the LEE pathogenicity island encoding the T3SS has been deleted	Pósfai et al. (1997)
RNE102	Derivative of E. coli Keio BW25113. The rne gene is HA- and His6-tagged and transcribed from a Plac promoter. Thus, IPTG is required for rne transcription. An ampicillin resistance marker is located upstream Plac	This study
RNE100	Derivative of E. coli Keio BW25113. The rne gene is HA- and His6-tagged and transcribed from the rne promoter	This study
MC4100	Non-pathogenic E. coli K-12 strain used as a positive control for P1 transduction experiments	Casadaban (1976)