Fig 2.

LEE regulation by AHLs. (A) Schematic of SdiA-AHL complex regulation of the LEE genes. SdiA complexed with AHLs binds to the LEE1 promoter to repress its expression. LEE1 encodes the Ler transcription activator of the LEE genes; hence, SdiA inhibition of LEE1 inhibits transcription of all LEE genes in a cascade fashion. (B) RT-qPCR analyses of ler (LEE1), espA (LLE4), and tir (LEE5) transcription in the wild type, wild type with exogenous AHLs, yenI⁺ strain (produces AHLs endogenously), wild type with vector (vector used to insert yenI into the EHEC chromosome, no AHLs, negative control), and wild type with vector plus endogenous AHLs. The mRNA levels are graphed as fold changes compared to WT levels. Statistical significance was determined by Student's t test; ***, P ≤ 0.001.