title: Multilocus sequence typing of Propionibacterium freudenreichii.
abstract: Propionibacterium freudenreichii is used as a ripening culture in Swiss cheese manufacture. This study investigates the molecular diversity and the population structure of this bacterium via multilocus sequence typing (MLST). Internal fragments of seven genes sequenced for 113 strains of different subspecies and origins allowed the resolution of 46 sequence types (STs) with occurrence frequencies ranging from 1 to 11. The core genome of the species harbours a low level of nucleotide polymorphism. In our data, single nucleotide polymorphisms account for only 2.28% of the concatenated sequences, and the average polymorphism rate in pairwise comparisons is 0.46%. The analyses reveal quantitatively comparable contributions of recombination and mutation in nucleotide changes at core genome loci along cell lineages. Remarkably, the STs exhibit little if any dairy biotope specialization. Phenotypic characterisation of the strains, based on their aptitude to use lactose and nitrate, shows that the two previously identified subspecies (freudenreichii and shermani) do not reflect the ancestral relationships in the P. freudenreichii population. The considerable phenotypic heterogeneity, found even at the ST level, suggests instead a history of recurrent switches between phenotypes.
authors.affiliation: INRA, UMR1253 Science et Technologie du Lait et de l'Œuf, F-35042 Rennes, France.
authors.forename: Marion
authors.initials: M
authors.lastname: Dalmasso
authors.forename: Pierre
authors.initials: P
authors.lastname: Nicolas
authors.forename: Hélène
authors.initials: H
authors.lastname: Falentin
authors.forename: Florence
authors.initials: F
authors.lastname: Valence
authors.forename: Jarna
authors.initials: J
authors.lastname: Tanskanen
authors.forename: Hanna
authors.initials: H
authors.lastname: Jatila
authors.forename: Tuomas
authors.initials: T
authors.lastname: Salusjärvi
authors.forename: Anne
authors.initials: A
authors.lastname: Thierry
mesh_terms: D000483:Alleles; D015373:Bacterial Typing Techniques; D004269:DNA, Bacterial / Q000235:genetics; D003611:Dairy Products / Q000382:microbiology; D005516:Food Microbiology; D005828:Genetics, Population; D058885:Multilocus Sequence Typing; D010641:Phenotype; D010802:Phylogeny; D011110:Polymorphism, Genetic; D011424:Propionibacterium / Q000145:classification / Q000235:genetics*; D011995:Recombination, Genetic; D017422:Sequence Analysis, DNA
chemical_list: D004269:DNA, Bacterial