A 38-Kilobase Pathogenicity Island Specific for Mycobacterium avium subsp. paratuberculosis Encodes Cell Surface Proteins Expressed in the Host

Abstract

ABSTRACT We have used representational difference analysis to identify a novel Mycobacterium avium subsp. paratuberculosis -specific ABC transporter operon ( mpt ), which comprises six open reading frames designated mptA to - F and is immediately preceded by two putative Fur boxes. Functional genomics revealed that the mpt operon is flanked on one end by a fep cluster encoding proteins involved in the uptake of Fe 3+ and on the other end by a sid cluster encoding non-ribosome-dependent heterocyclic siderophore synthases. Together these genes form a 38-kb M. avium subsp. paratuberculosis -specific locus flanked by an insertion sequence similar to IS 1110 . Expression studies using Western blot analyses showed that MptC is present in the envelope fraction of M. avium subsp. paratuberculosis . The MptD protein was shown to be surface exposed, using a specific phage (fMptD) isolated from a phage-peptide library, by differential screening of Mycobacterium smegmatis transformants. The phage fMptD-derived peptide could be used in a peptide-mediated capture PCR with milk from infected dairy herds, thereby showing surface-exposed expression of the MptD protein in the host. Together, these data suggest that the 38-kb locus constitutes an M. avium subsp. paratuberculosis pathogenicity island.