Submitted to: Journal of Bacteriology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 5, 1996
Publication Date: N/A
Interpretive Summary: We recently discovered a bacteriophage and named it VSH-1 (Virus of S. hyodysenteriae). VSH-1 kills cells of the spirochete Serpulina hyodysenteriae, the bacterial pathogen that causes swine dysentery, a world-wide disease estimated to cost the U.S. pork industry $100 million per year. Vaccines for this disease are not available because it has not been commercially practical to produce S. hyodysenteriae in large-scale fermentation cultures. We found VSH-1 is a lamboid-shaped virus containing double-stranded DNA, 7.5 kilobase pairs in size. Surprisingly, the genetic material (DNA) of VSH-1 consists almost entirely of fragments of S. hyodysenteriae genetic material. We also found that VSH-1 was able to transfer bacterial genes between S. hyodysenteriae cells. This is the first report of gene exchange between cells of any spirochete. As a parasite, VSH-1 could be a natural biocontrol agent of S. hyodysenteriae, and a substitute for antibiotics in feeds. As a gene transfer mechanism, the virus could be used to isolate specific protective antigens and produce nonvirulent strains of S. hyodysenteriae, as vaccine strains. This information is useful to scientists studying viruses and to veterinary biologics researchers developing antibiotics or vaccines for controlling swine industry and other spirochete diseases. Ultimately, the swine producer may benefit if VSH-1 can be developed into a treatment for swine dysentery. Using viruses to control bacterial disease is a new approach that is potentially less costly and with fewer damaging environmental effects than the current stragegy of antibiotic use.
Technical Abstract: Serpulina hyodysenteriae B204 cells treated with mitomycin C (20 ug/ml culture broth), lysed and released bacteriophages. Bacteriophage particles, precipitated by using PEG and purified by CsCl density gradient ultracentrifugation, had a buoyant density of 1.375 g/cm**3 and consisted of a head (45 nm diameter) and a ultrastructurally simple (noncontractile) tail (64 nm x 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-1 was incapable of lytic growth on any of 5 intestinal spirochete strains, representing 3 Serpulina species. VSH-1 nucleic acid was determined to be approximately 7.5 kb in size, 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 Ssp I, Ase I, EcoR V, and Afl II gave electrophoretic banding patterns nearly identical to those of digested S. hyodysenteriae chromosomal DNA. Additionally, VSH-1 DNA fragments hybridized with probes complementary to S. hyodysenteriae chromosomal genes nox and flaA1. When purified bacteriophages induced from cultures of S. hyodysenteriae strain 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/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