FIG. 1.

Structure and sequence of CTX prophages within AS207, an O139 Calcutta strain of V. cholerae. (A) Within the AS207 chromosome, an RS1 element and a CTX^ET prophage are followed by two CTX^calc prophages (shown in light grey). The Calcutta prophage is structurally similar to the previously described CTX prophages within El Tor and classical strains, which contain two major domains known as RS2 and core. RS2 contains three genes (rstA, rstB, and rstR) whose transcriptional orientation is indicated by the arrows. The black triangles represent attRS-ER sequences. (B) Alignment of the nucleotide sequences of rstR, ig-2, and parts of rstA and ig-1 from Calcutta, El Tor, and classical prophages. The arrows underneath the sequences depict the ORFs that encode the three variants of RstR.