title: The majority of lactococcal plasmids carry a highly related replicon.
abstract: DNA sequence analysis and Southern hybridizations, together with complementation experiments, were used to study relationships between lactococcal plasmid replicons. pWVO2, pWVO4 and pWVO5, which co-exist in Lactococcus lactis subsp. cremoris Wg2, and pIL7 (isolated from another strain) all contained a functional replication region which appeared to be very similar to that of some known lactococcal plasmids. They contain a gene encoding a highly conserved RepB protein (60-80% amino acid identity between pWVO2, pWVO4 and pWVO5), which is essential for replication. When supplied in trans, repB of pWVO2 complemented a repB deficiency of pWVO5. Upstream of the repB gene, all these plasmids contain a strongly conserved region including a 22 bp sequence tandemly repeated three-and-a-half times, and an A/T-rich region. The similarity with pWVO2, which is known to replicate via a theta mechanism, suggests that all plasmids of this family are capable of theta replication. Southern hybridizations revealed that many lactococcal strains contain plasmids of this family.
authors.affiliation: Department of Genetics, Centre of Biological Sciences, Haren, The Netherlands.
authors.forename: J F
authors.initials: JF
authors.lastname: Seegers
authors.forename: S
authors.initials: S
authors.lastname: Bron
authors.forename: C M
authors.initials: CM
authors.lastname: Franke
authors.forename: G
authors.initials: G
authors.lastname: Venema
authors.forename: R
authors.initials: R
authors.lastname: Kiewiet
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics; D001483:Base Sequence; D015139:Blotting, Southern; D004261:DNA Replication; D004269:DNA, Bacterial / Q000235:genetics*; D005798:Genes, Bacterial; D005816:Genetic Complementation Test; D013294:Lactococcus lactis / Q000235:genetics*; D008969:Molecular Sequence Data; D016366:Open Reading Frames / Q000235:genetics; D010957:Plasmids / Q000145:classification / Q000235:genetics*; D012093:Replicon; D016415:Sequence Alignment; D012689:Sequence Homology, Nucleic Acid; D013045:Species Specificity
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; C048817:RepB protein, Bacteria