Phenotypic and genetic traits of porcine intestinal spirochete strain P43/6/78' (= ATCC 51139T) (T = type strain), which is pathogenic and weakly beta-hemolytic, were determined in order to confirm the taxonomic position of this organism and its relationships to previously described species of intestinal spirochetes. In BHIS broth, P43/6/7ST cells had a doubling time of 1 to 2 h and grew to a maximum cell density of 2 X 10' cells per ml at 37 to 42°C. They hydrolyzed hippurate, utilized D-glucose, D-fructose, sucrose, D-trehalose, u-galactose, D-mannose, maltose, N-acetyl-D-glucosamine, D-glucosamine, pyruvate, L-fucose, D-cellobiose, and D-ribose as growth substrates, and produced acetate, butyrate, ethanol, H,, and CO, as metabolic products. They consumed substrate amounts of oxygen and had a G+C content (24.6 mol%) similar to that of Serpulina hyodysenteriue B7ST (25.9 mol%). Phenotypic traits that could be used to distinguish strain P43/6/78' from S. hyodysenteriue and Serpulina innocens included its ultrastructural appearance (each strain P43/6/78' cell had 8 or 10 periplasmic flagella, with 4 or 5 flagella inserted at each end, and the cells were thinner and shorter and had more pointed ends than S. hyodysenteriae and S. innocens cells), its faster growth rate in liquid media, its hydrolysis of hippurate, its lack of P-glucosidase activity, and its metabolism of D-ribose. DNA-DNA relative reassociation experiments in which the Sl nuclease method was used revealed that P43/6/7ST was related to, but was genetically distinct from, both S. hyodysenteriae B78' (level of sequence homology, 25 to 32%) and S. innocens B256T (level of sequence homology, 24 to 25%). These and previous results indicate that intestinal spirochete strain P43/6/7ST represents a distinct Serpulina species. Therefore, we propose that strain P43/6/78 should be designated as the type strain of a new species, Serpulina pilosicoli.Porcine intestinal spirochetosis or spirochetal diarrhea is a disease of swine that are between 4 and 20 weeks old but typically occurs within 7 to 14 days after weaning (7, 39). The clinical signs of this disease include mucus-containing, usually nonbloody diarrhea; poor feed conversion; and depressed growth rates (1, 7, 31,40). The characteristic histological feature that distinguishes porcine intestinal spirochetosis is a dense mat or false brush border of spirochete cells which are closely packed parallel to one another and are attached by one end to the colonic epithelium (4, 7, 14,40). Such cells are not typical of infections caused by Serpulina hyodysenteriae (the agent of swine dysentery), but have been found in humans colonized by intestinal spirochetes, where their clinical significance is unclear (8, 22).The etiologic agent of porcine intestinal spirochetosis was first described in 1980 by Taylor et al. (40). These investigators successfully isolated an intestinal spirochete, designated strain P43/6/78T (T = type strain), and reproduced clinical signs and lesions typical of the disease in pigs that were o...

Serpulina hyodysenteriae B204 cells treated with mitomycin (20 g 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/cm 3 and consisted of a head (45-nm diameter) and an ultrastructurally simple (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 and flaA1. When purified bacteriophages induced from cultures of S. hyodysenteriae A203 (⌬flaA1 593-762::cat) were added to growing cells of strain A216 (⌬nox 438-760::kan), transductants (Cm r Km r ) were obtained at a frequency of 1.5 ؋ 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.Natural gene transfer mechanisms (conjugative plasmids and transducing bacteriophages) have not been demonstrated for spirochetes. Indirect evidence of lateral gene transfer has been obtained for Borrelia spp. (16). The existence of DNAfilled membrane vesicles on the surfaces of Borrelia burgdorferi cells has been reported, although their possible role in gene transfer is unknown (7). In addition, several extrachromosomal elements have been identified in B. burgdorferi, and an extrachromosomal plasmid of 2.6 kb has been isolated from Treponema denticola and characterized (10,25). In cultures of various spirochetes, bacteriophages have been observed free, attached to cells, or within cells as noted previously (9). Three lytic phages of Leptospira biflexa have been isolated and characterized (24). However, to our knowledge, there is no evidence that these three phages play a role in gene transfer.The spirochete Serpulina hyodysenteriae causes swine dysentery, an enteric disease producing a severe mucohemorrhagic diarrhea in infected swine (8). Potential genetic transfer elements for S. hyodysenteriae have been identified. Ritchie and colleagues observed bacteriophages with the same morphology in 18 different cultures of S. hyodysente...

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