title: Unprecedented large inverted repeats at the replication terminus of circular bacterial chromosomes suggest a novel mode of chromosome rescue.
abstract: The first Lactobacillus delbrueckii ssp. bulgaricus genome sequence revealed the presence of a very large inverted repeat (IR), a DNA sequence arrangement which thus far seemed inconceivable in a non-manipulated circular bacterial chromosome, at the replication terminus. This intriguing observation prompted us to investigate if similar IRs could be found in other bacteria. IRs with sizes varying from 38 to 76 kbp were found at the replication terminus of all 5 L. delbrueckii ssp. bulgaricus chromosomes analysed, but in none of 1373 other chromosomes. They represent the first naturally occurring very large IRs detected in circular bacterial genomes. A comparison of the L. bulgaricus replication terminus regions and the corresponding regions without IR in 5 L. delbrueckii ssp. lactis genomes leads us to propose a model for the formation and evolution of the IRs. The DNA sequence data are consistent with a novel model of chromosome rescue after premature replication termination or irreversible chromosome damage near the replication terminus, involving mechanisms analogous to those proposed in the formation of very large IRs in human cancer cells. We postulate that the L. delbrueckii ssp. bulgaricus-specific IRs in different strains derive from a single ancestral IR of at least 93 kbp.
authors.affiliation: Micalis Institute, INRA, AgroParisTech, Université Paris-Saclay, 78350 Jouy-en-Josas, France.
authors.forename: Hela
authors.initials: H
authors.lastname: El Kafsi
authors.affiliation: MaIAGE, INRA, Université Paris-Saclay, 78350 Jouy-en-Josas, France.
authors.forename: Valentin
authors.initials: V
authors.lastname: Loux
authors.affiliation: MaIAGE, INRA, Université Paris-Saclay, 78350 Jouy-en-Josas, France.
authors.forename: Mahendra
authors.initials: M
authors.lastname: Mariadassou
authors.affiliation: MaIAGE, INRA, Université Paris-Saclay, 78350 Jouy-en-Josas, France.
authors.forename: Camille
authors.initials: C
authors.lastname: Blin
authors.affiliation: MaIAGE, INRA, Université Paris-Saclay, 78350 Jouy-en-Josas, France.
authors.forename: Hélène
authors.initials: H
authors.lastname: Chiapello
authors.affiliation: Micalis Institute, INRA, AgroParisTech, Université Paris-Saclay, 78350 Jouy-en-Josas, France.
authors.forename: Anne-Laure
authors.initials: AL
authors.lastname: Abraham
authors.affiliation: Micalis Institute, INRA, AgroParisTech, Université Paris-Saclay, 78350 Jouy-en-Josas, France.
authors.forename: Emmanuelle
authors.initials: E
authors.lastname: Maguin
authors.affiliation: Micalis Institute, INRA, AgroParisTech, Université Paris-Saclay, 78350 Jouy-en-Josas, France.
authors.forename: Maarten
authors.initials: M
authors.lastname: van de Guchte
mesh_terms: D002876:Chromosomes, Bacterial / Q000737:chemistry*; D004261:DNA Replication; D004269:DNA, Bacterial / Q000235:genetics*; D004270:DNA, Circular / Q000235:genetics; D019143:Evolution, Molecular; D016680:Genome, Bacterial; D055029:Inverted Repeat Sequences; D048668:Lactobacillus delbrueckii / Q000145:classification / Q000235:genetics*; D008957:Models, Genetic; D010802:Phylogeny; D017422:Sequence Analysis, DNA
chemical_list: D004269:DNA, Bacterial; D004270:DNA, Circular