Purification and characterization of VSH-1, a generalized transducing bacteriophage of Serpulina hyodysenteriae

Serpulina hyodysenteriae B204 cells treated with mitomycin (20 micrograms of mitomycin/ml of culture broth) lysed and released bacteriophages. Bacteriophage particles, precipitated by using polyethylene glycol and purified by CsCl density gradient ultracentrifugation, had a buoyant density of 1.375 g/cm3 and consisted of a head (45-nm diameter) and an ultrastructurally ample (noncontractile) tail (64 by 9 nm) composed of at least 13 proteins with molecular masses ranging between 13 and 101 kDa. The purified bacteriophage has been designated VSH-1 (VSH for virus of S. hyodysenteriae). VSH-1 was incapable of lytic growth on any of five intestinal spirochete strains, representing three Serpulina species. VSH-1 nucleic acid was determined to be approximately 7.5 kb in size and to be linear, double-stranded DNA based on differential staining with acridine orange, DNase I sensitivity, electrophoretic mobility, and contour length as measured by electron microscopy. Phage DNA digested by the restriction enzymes SspI, AseI, EcoRV, and AflII gave electrophoretic banding patterns nearly identical to those of digested chromosomal DNA from S. hyodysenteriae. Additionally, VSH-1 DNA fragments hybridized with probes complementary to S. hyodysenteriae chromosomal genes nox flaA1. When purified bacteriophages induced from cultures of S. hyodysenteriae A203 (delta flaA1 593-762::cat) were added to growing cells of strain A216 (delta nox 438-760::kan), transductants (Cm(r) Km(r)) were obtained at a frequency of 1.5 X 10-6 per phage particle (enumerated by electron microscopy). These findings indicate that induced VSH-1 virions package DNA of S. hyodysenteriae and are capable of transferring host genes between cells of that spirochete. To our knowledge, this is the first report of genetic transduction of a spirochete.