Comparison of the genetic structures of the two CTX prophage arrays identified in the V. cholerae strains under study. Both prophages are integrated into the large chromosome. Arrows indicate the transcription direction of each gene. (A) CTX prophage array profile A: RS1-RS2-CORE; (B) CTX prophage array profile B: RS2-CORE-RS1. Map is not to scale. rstRET (purple arrow): El Tor type rtsR; ctxBET (red arrow): El Tor type ctxB; ctxBcla (yellow arrow): Classical type ctxB; TLC: toxin-linked cryptic plasmid; RTX: RTX (repeat in toxin) gene cluster.