title: Genomic rearrangements at rrn operons in Salmonella.
abstract: Most Salmonella serovars are general pathogens that infect a variety of hosts. These "generalist" serovars cause disease in many animals from reptiles to mammals. In contrast, a few serovars cause disease only in a specific host. Host-specific serovars can cause a systemic, often fatal disease in one species yet remain avirulent in other species. Host-specific Salmonella frequently have large genomic rearrangements due to recombination at the ribosomal RNA (rrn) operons while the generalists consistently have a conserved chromosomal arrangement. To determine whether this is the result of an intrinsic difference in recombination frequency or a consequence of lifestyle difference between generalist and host-specific Salmonella, we determined the frequency of rearrangements in vitro. Using lacZ genes as portable regions of homology for inversion analysis, we found that both generalist and host-specific serovars of Salmonella have similar tolerances to chromosomal rearrangements in vitro. Using PCR and genetic selection, we found that generalist and host-specific serovars also undergo rearrangements at rrn operons at similar frequencies in vitro. These observations indicate that the observed difference in genomic stability between generalist and host-specific serovars is a consequence of their distinct lifestyles, not intrinsic differences in recombination frequencies.
authors.affiliation: Department of Microbiology, University of Illinois, Urbana, Illinois 61801, USA.
authors.forename: R Allen
authors.initials: RA
authors.lastname: Helm
authors.forename: Alison G
authors.initials: AG
authors.lastname: Lee
authors.forename: Harry D
authors.initials: HD
authors.lastname: Christman
authors.forename: Stanley
authors.initials: S
authors.lastname: Maloy
mesh_terms: D001483:Base Sequence; D007446:Chromosome Inversion; D017931:DNA Primers; D007763:Lac Operon; D009876:Operon; D012335:RNA, Ribosomal / Q000235:genetics*; D012475:Salmonella / Q000235:genetics*
chemical_list: D017931:DNA Primers; D012335:RNA, Ribosomal