PHYSICAL AND GENETIC-MAP OF THE SERPULINA-HYODYSENTERIAE B78(T) CHROMOSOME

A combined physical and genetic map of the Serpulina hyodysenteriae B7 8(T) genome was constructed by using pulsed-field gel electrophoresis and DNA blot hybridizations. The S. hyodysenteriae genome is a single circular chromosome about 3.2 Mb in size. The physical map of the chro mosome was constructed with the restriction enzymes BssHII, EclXI, Not I, SalI, and SmaI. The physical map was used to construct a linkage ma p for genes encoding rRNA, flagellum subunit proteins, DNA gyrase, NAD H oxidase, and three distinct hemolysins. Several flaB2-related loci, encoding core flagellum subunit proteins, were detected and are disper sed around the chromosome. The rRNA gene organization in S. hyodysente riae is unusual, S. hyodysenteriae has one gene each for 5S (rrf), 16S (rrs), and 23S (rrl) rRNAs. The rrf and rrl genes are closely linked (within 5 kb), while the rrs gene is about 860 kb from the other two r RNA genes. Using a probe for the S. hyodysenteriae gyrA gene, we ident ified a possible location for the chromosomal replication origin. The size and genetic organization of the S. hyodysenteriae chromosome are different from those of previously characterized spirochetes.