VEJφ, a novel filamentous phage of Vibrio cholerae able to transduce the cholera toxin genes

A novel filamentous bacteriophage, designated VEJphi, was isolated from strain MO45 of Vibrio cholerae of the O139 serogroup. A molecular characterization of the phage was carried out, which included sequencing of its whole genome, study of the genomic structure, identification of the phage receptor, and determination of the function of some of the genes, such as those encoding the major capsid protein and the single-stranded DNA-binding protein. The genome nucleotide sequence of VEJphi, which consists of 6842 bp, revealed that it is organized in modules of functionally related genes in an array that is characteristic of the genus Inovirus (filamentous phages). VEJphi is closely related to other previously described filamentous phages of V. cholerae, including VGJphi, VSK and fs1. Like these phages, VEJphi uses as a cellular receptor the type IV fimbria called the mannose-sensitive haemagglutinin (MSHA). It was also demonstrated that VEJphi, like phage VGJphi, is able to transmit the genome of phage CTXphi, and therefore the genes encoding the cholera toxin (CT), horizontally among populations of V. cholerae expressing the MSHA receptor fimbria. This suggests that the variety of phages implicated in the horizontal transmission of the CT genes could be more diverse than formerly thought.