Author
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Zuerner, Richard |
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Submitted to: Meeting Abstract
Publication Type: Abstract Only Publication Acceptance Date: 2/20/2003 Publication Date: 3/1/2003 Citation: Zuerner, R.L. 2003. Comparative analysis of brachyspira genomes [abstract]. 2nd international conference on colonic spirochaetal infections in animals and humans. pg. 25. Interpretive Summary: Technical Abstract: Brachyspira pilosicoli and B. hyodysenteriae are related intestinal pathogens that exhibit different host range and virulence. Brachyspira can exchange DNA via the gene transfer agent, VSH-1, and this process may have a profound impact on the evolution of this genus. We have limited information on the size, structure, and organization of Brachyspira genomes. Construction of a combined physical and genetic map of B. hyodysenteriae revealed a single circular chromosome about 3.2 Mbp in size. Virtually nothing is known about the organization of the B. pilosicoli genome. To better understand the differences and similarities of these two species, we constructed a combined physical and genetic map of the B. pilosicoli genome and compared it to the previously constructed B. hyodysenteriae map. The B. pilosicoli genome is composed of a single circular chromosome 2.5 Mbp in size. The B. pilosicoli and B. hyodysenteriae genomes differ in organization due to the presence of several chromosomal rearrangements. Because differences in genetic content and organization will influence phenotype, we compared several loci encoding potential virulence factors to identify possible differences between B. pilosicoli and B. hyodysenteriae that may affect the ability to cause disease. We confirmed that the bit locus, a cluster of iron regulated B. hyodysenteriae genes, are not detectable in B. pilosicoli. In contrast, hybridization analysis showed the presence of the hlyA gene. In B. hyodysenteriae the hlyA gene encodes an acyl-carrier protein (ACP) associated with ß-hemolysin. Sequence analysis of the B. hyodysenteriae hlyA locus allowed identification of two genes encoding proteins associated with ACP processing, fabG, an ACP-reductase, and fabF, an ACP-synthase, that flank hlyA. Although hlyA is well conserved between B. pilosicoli and B. hyodysenteriae, the intergenic regions are quite divergent. This sequence variation may affect hylA expression in B. pilosicoli. Furthermore, lack of sequence homology in intergenic regions may present a barrier to efficient gene exchange between Brachyspira species. Construction of these combined maps, and their comparison, should facilitate genomic sequencing of these bacteria. |
