FIGURE 1.

Genetic arrangement of RS1, CTX and TLC (RCT) prophages in the large chromosome of Vibrio cholerae O1 strain. (A) genomic DNA (gDNA) of a wild-type V. cholerae E7946 strain was used as the donor DNA in chitin-induced transformation, encompassing 21,153-bp encoding RCT which was genetically marked with a kanamycin resistance cassette (kan^R) (note, kan^R at the top of orfU gene) replacing orfU gene in CTX prophage. The arrows show either gene name, VC followed by a number or ORF designation. (B) Env-9 rif^R, served as a recipient strain in chitin-induced transformation, lacking the RCT prophages while retaining a 381-bp non-coding region that is present between rtxA (VC1451) and VC1479 encoding a hypothetical protein. (C) following chitin-induced transformation, Env-9 rif^R acquired kan^R-marked RCT prophages mirror-imaging RCT of E7946 kan^R; the newly created transformant was designated as AAS91. (D) fourteen convergent PCR primer sets were used to amplify 14 PCR fragments (1–14) confirming all 27 genes present in the RCT prophages both in donor E7946 and transformant AAS91strains. A plus (+) sign indicates presence of the amplicon sequences spanning the targeted region in RCT prophages.