Fig. 3. Transcriptional regulation and functional identification of the hcp2B and hcp2A clusters.

a The 50% duck serum in minimal medium activated the transcription of hcp2B-vgrG2 and hcp2A-vipA at different levels. b H-NS repressed transcription of the hcp2B cluster in LB-rich culture. The gene expression levels in the indicated conditions were analyzed by qRT-PCR. c Operon identification of hcp2B-vgrG2. The hcp2B and vgrG2 genes formed one operon that deviated from the major cluster represented based on reverse transcription PCR, and a negative control was set up without reverse transcriptase. d Growth competition assays for the XmtU/XmtV pair between the indicated APEC donor and recipient strains. Experiments were initiated with equal CFUs of donor and recipient bacteria, as denoted by the dashed line. Asterisks indicate significant differences in competition outcomes between recipient strains against the same donor strain (**p < 0.01). Error bars indicate standard deviations for three independent experiments