title: New insights about phenotypic heterogeneity withinPropionibacterium freudenreichiiargue against its division into subspecies.
abstract: Propionibacterium freudenreichiiis widely used in Swiss-type cheese manufacture, where it contributes to flavour and eye development. It is currently divided into two subspecies, according to the phenotype for lactose fermentation and nitrate reduction (lac+/nit-and lac-/nit+forP. freudenreichiisubsp.shermaniiand subsp.freudenreichii, respectively). However, the existence of unclassifiable strains (lac+/nit+and lac-/nit-) has also been reported. The aim of this study was to revisit the relevance of the subdivision ofP. freudenreichiiinto subspecies, by confirming the existence of unclassifiable strains. Relevant conditions to test the ability ofP. freudenreichiifor lactose fermentation and nitrate reduction were first determined, by using 10 sequenced strains, in which the presence or absence of the lactose and nitrate genomic islands were known. We also determined whether the subdivision based on lac/nit phenotype was related to other phenotypic properties of interest in cheese manufacture, in this case, the production of aroma compounds, analysed by gas chromatography-mass spectrometry, for a total of 28 strains. The results showed that a too short incubation time can lead to false negative for lactose fermentation and nitrate reduction. They confirmed the existence of four lac/nit phenotypes instead of the two expected, thus leading to 13 unclassifiable strains out of the 28 characterized (7 lac+/nit+and 6 lac-/nit-). The production of the 15 aroma compounds detected in all cultures varied more within a lac/nit phenotype (up to 20 times) than between them. Taken together, these results demonstrate that the division ofP. freudenreichiiinto two subspecies does not appear to be relevant.
authors.affiliation: Departamento de Tecnologia de Alimentos, Universidade Federal de Viçosa, Viçosa, MG Brazil ; INRA, UMR1253 Science et Technologie du Lait et de l'OEuf, 35042 Rennes, France ; AGROCAMPUS OUEST, UMR1253 Science et Technologie du Lait et de l'OEuf, 35042 Rennes, France.
authors.forename: Rosangela
authors.initials: R
authors.lastname: de Freitas
authors.affiliation: INRA, UMR1253 Science et Technologie du Lait et de l'OEuf, 35042 Rennes, France ; AGROCAMPUS OUEST, UMR1253 Science et Technologie du Lait et de l'OEuf, 35042 Rennes, France.
authors.forename: Marie-Noelle
authors.initials: MN
authors.lastname: Madec
authors.affiliation: INRA, UMR1253 Science et Technologie du Lait et de l'OEuf, 35042 Rennes, France ; AGROCAMPUS OUEST, UMR1253 Science et Technologie du Lait et de l'OEuf, 35042 Rennes, France.
authors.forename: Victoria
authors.initials: V
authors.lastname: Chuat
authors.affiliation: INRA, UMR1253 Science et Technologie du Lait et de l'OEuf, 35042 Rennes, France ; AGROCAMPUS OUEST, UMR1253 Science et Technologie du Lait et de l'OEuf, 35042 Rennes, France.
authors.forename: Marie-Bernadette
authors.initials: MB
authors.lastname: Maillard
authors.affiliation: INRA, UMR1253 Science et Technologie du Lait et de l'OEuf, 35042 Rennes, France ; AGROCAMPUS OUEST, UMR1253 Science et Technologie du Lait et de l'OEuf, 35042 Rennes, France ; Centro de Referencia para Lactobacilos (CERELA-CONICET), Chacabuco 145, (4000), Tucumán, Argentina.
authors.forename: María C Abeijón
authors.initials: MC
authors.lastname: Mukdsi
authors.affiliation: INRA, UMR1253 Science et Technologie du Lait et de l'OEuf, 35042 Rennes, France ; AGROCAMPUS OUEST, UMR1253 Science et Technologie du Lait et de l'OEuf, 35042 Rennes, France.
authors.forename: Hélène
authors.initials: H
authors.lastname: Falentin
authors.affiliation: Departamento de Tecnologia de Alimentos, Universidade Federal de Viçosa, Viçosa, MG Brazil.
authors.forename: Antonio Fernandes
authors.initials: AF
authors.lastname: de Carvalho
authors.affiliation: INRA, UMR1253 Science et Technologie du Lait et de l'OEuf, 35042 Rennes, France ; AGROCAMPUS OUEST, UMR1253 Science et Technologie du Lait et de l'OEuf, 35042 Rennes, France.
authors.forename: Florence
authors.initials: F
authors.lastname: Valence
authors.affiliation: INRA, UMR1253 Science et Technologie du Lait et de l'OEuf, 35042 Rennes, France ; AGROCAMPUS OUEST, UMR1253 Science et Technologie du Lait et de l'OEuf, 35042 Rennes, France.
authors.forename: Anne
authors.initials: A
authors.lastname: Thierry
keywords: Biodiversity; Flavour compound; Propionibacteria; Subspecies; Volatile fingerprint