Certain
Liu et al. found that the bacteriophage BPP-1 (Bvg plus tropic phage-1) had a tropism for the Bvg+ phase bacteria. They identified the prn gene, encoding the adhesin pertactin, as essential for tropism, and were able to isolate bacteriophage variants with different tropisms, implying a mechanism of tropic switching. They then looked at tropic variants and noticed a 134 bp repeat sequence within the mtd (major tropism determinant) locus, which is repeated in an adjacent brt locus encoding a Bordetella reverse transcriptase enzyme. The brt repeat and ...