Submitted to: Federation of European Microbiological Societies Microbiology Letters
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 4, 1995
Publication Date: N/A
Interpretive Summary: In this research, we determined how to stimulate viruses to come out of the DNA of Serpulina hyodysenteriae. S. hyodysenteriae is a bacterium and the etiologic agent of the disease swine dysentery. These viruses, known as bacteriophages, are intracellular parasites of S. hyodysenteriae. Consequently, when they are induced, these bacteriophages destroy S. hyodysenteriae cells. There are two features of these viruses that could be significant in controlling swine dysentery. First, viruses like these are useful in recombinant DNA research, for transferring the genes of bacteria like S. hyodysenteriae. Gene transfer by a virus would provide an important tool for determining S. hyodysenteriae virulence genes and for making attenuated strains to be tested in vaccines. Second, if the viruses are induced during an infection, in animals suffering from swine dysentery, the viruses would kill S. hyodysenteriae cells and therefore could limit the severity or duration of the disease. Current research is aimed at determining whether or not the virus is produced in animals with swine dysentery and whether the virus could be a natural "biocontrol" mechanism for this swine disease.
Technical Abstract: A prophage was induced from cells of the pathogenic spirochaete Serpulina hyodysenteriae using mitomycin C. Five to seven hours after mitomycin C was added (8 ug/ml, final conc.) to S. hyodysenteriae B204 cultures in BHIS broth (OD620=0.9) cell lysis was detected as a decrease in culture optical density. Bacteriophage particles attached to whole cells and to cell debris were detected by electron microscopic analysis of negatively stained (2% PTA, pH 7.0) bacteria harvested by centrifugation from mitomycin C treated cultures. The phage particles consisted of a head (45 nm diameter) and a tail (64 nm x 9 nm). Bacteria from untreated cultures lacked phages detectable by electron microscopy. The appearance of bacteriophage particles in mitomycin C treated cultures correlates well with the appearance of an extrachromosomal DNA molecule (migration rate between 7 - 8 kb ds DNA in agarose gel electrophoresis). This extrachromosomal DNA molecule is therefore likely to originate from phage. When cultures of other S. hyodysenteriae strains (B78, B169, A-1, B8044, B6933, Ack300/8, R-1) and S. innocens 4/71 in BHIS were treated with mitomycin C (8-15 ug/ml, final conc.), phages similar in morphology and size to the S. hyodysenteriae B204 phage were induced.