A Illustration of the VpT6SS1 (vp1386-vp1420) activation cascade. Genes are represented by arrows indicating the direction of transcription. Genes belonging to the same operon are denoted by the same color. Locus numbers (vpxxxx) are denoted above. Positive regulators are denoted by a red frame. Dashed arrows denote transcriptional activation and are color coded according to the relevant induced operon. Numbers in black circles next to the positive regulators TfoY, VP1407, and VP1391 delineate the progression of the cascade. 