title: Recent horizontal transmission of plasmids between natural populations of Escherichia coli and Salmonella enterica.
abstract: Seventy-one natural isolates obtained from a Salmonella reference collection were examined for the presence of plasmids closely related to the Escherichia coli F plasmid. The collection consists of several serovars of the S. enterica Typhimurium complex, subspecies I, to which 99% of pathogenic salmonellae belong. Molecular genetic techniques of DNA hybridization, along with PCR and DNA sequencing, were used to examine the occurrence, distribution, and genetic diversity of F-like plasmids among Salmonella strains. The F plasmid genes examined were finO, traD, traY, and repA, which map at dispersed positions on the F plasmid of E. coli. Comparative sequence analysis of each of the four genes in Salmonella plasmids showed them to be homologous (in some cases, virtually identical) to those found in F plasmids of E. coli natural isolates. Furthermore, the frequency of F-like plasmids in Salmonella strains was approximately the same as that observed in the E. coli Reference Collection. However, in Salmonella, the distribution was confined predominately to the serovars Typhimurium and Muenchen. The unexpected finding of a shared pool of F-like plasmids between S. enterica and E. coli demonstrates the significant role of conjugation in the histories of these important bacterial species.
authors.affiliation: Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts 02138, USA.
authors.forename: E F
authors.initials: EF
authors.lastname: Boyd
authors.forename: D L
authors.initials: DL
authors.lastname: Hartl
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics; D003227:Conjugation, Genetic; D004265:DNA Helicases; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics*; D029968:Escherichia coli Proteins; D005144:F Factor; D008565:Membrane Proteins; D008969:Molecular Sequence Data; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D011110:Polymorphism, Genetic; D011506:Proteins / Q000737:chemistry / Q000235:genetics; D016601:RNA-Binding Proteins; D012097:Repressor Proteins; D012475:Salmonella / Q000235:genetics*; D012486:Salmonella typhimurium / Q000235:genetics*; D015534:Trans-Activators
chemical_list: D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; D008565:Membrane Proteins; D011506:Proteins; D016601:RNA-Binding Proteins; D012097:Repressor Proteins; D015534:Trans-Activators; C045264:replication initiator protein; C064957:traD protein, E coli; C063238:traY protein, E coli; C074275:FinO protein, E coli; D004265:DNA Helicases