IRON TRANSPORT GENES OF THE PJM1-MEDIATED IRON UPTAKE SYSTEM OF VIBRIO-ANGUILLARUM ARE INCLUDED IN A TRANSPOSON-LIKE STRUCTURE

The pJM1 genes encoding the proteins involved in iron transport in the anguibactin iron uptake system were found to be flanked by insertion sequences in a composite transposonlike structure. These Vibrio anguil larum insertion sequences, ISV-A1 and ISV-A2, are related to IS903, IS 102, and the ISVs found in Vibrio parahaemoliticus, Vibrio mimicus, an d non-O1 Vibrio cholerae flanking various tdh (thermostable direct hem olysin) genes. The inverted repeats at the ends of ISV-A1 and ISV-A2 h ave no more than three mismatches when compared to the inverted repeat s of the other ISVs or IS903 and IS102. ISV-A1 and ISV-A2 are flanked by 9-bp direct repeats, which is the number of bases that are duplicat ed upon IS903 or IS102 transposition. The similarities found between t he V. anguillarum ISVs and the other ISVs as well as IS903 and IS102 s uggest that they derive from a common ancestral insertion sequence. At the end of ISV-A1 there is a -35 sequence region followed by a -10 se quence found in the pJM1 sequence immediately outside the ISV. This pr omoter region is followed by an open reading frame with the potential to encode a polypeptide of 26,985 Da whose function is still unknown. The functionality of this promoter has been demonstrated and expressio n analysis showed that the promoter is regulated by the iron concentra tion of the media. (C) 1995 Academic Press. Inc.