Two different CTXΦ prophage genomes present on the chromosomes of Vibrio cholerae serogroup O139 strains and multiformity of their concomitance
Objective To study the diversity of bacteriophage CTXΦ genomes in serogroup O139 strains of Vibrio cholerae that harbored two types of CTXΦ genome. Methods Some strains with distinct variance in copy number of ctxAB and zot of CTXΦ were detected by Southern blot and selected as the templets, fragments containing the suppressor gene rstR were amplified, sequenced and analysed. Results The rstR containing fragments which were amplified with primers designed according to the conservative regions presented two different amplicons in length with these strains, implying that two types of CTXΦ genomes coexist in the chromosome of the 3 strains, i.e., one CTXΦ genome that encodes ctxAB, and another CTXΦ genome without ctxAB. These amplicons were further cloned and sequenced. By homology searching in GenBank, three different co existence of CTXΦ genomes in the 3 strains were found. Conclusion Different CTXΦ genomes with different sequence of rstR coexist in the same strain. The complexity in the process of evolution in the CTXΦ family and the appearance, transfer of CTXΦ family in various serogroups or biotypes of V.cholerae may show divergence of V.cholerae strains. [