title: The long-term survival of Propionibacterium freudenreichii in a context of nutrient shortage.
abstract: OBJECTIVE
  Propionibacterium freudenreichii is an actinobacterium widely used in dairy industry during the ripening process of Swiss-type cheeses and which presents probiotic properties. P. freudenreichii is reportedly a hardy bacterium, able to survive during the cheese-making process and when subjected to digestive stresses. During this study the long-term survival (LTS) of P. freudenreichii was investigated for 11 days by means of phenotypic characterization in a culture medium without the addition of any nutrients.
  
  
  RESULTS
  For 11 days, in a non-nutrient supplemented culture medium, eight strains were monitored by measuring their optical density, counting colony-forming units (CFU) and using LIVE/DEAD staining and microscopy observation. Under these conditions, all strains displayed high survival rates in the culture medium, their culturability reaching more than 9 log10 CFU ml(-1) after 2 days. After 11 days, this value ranged from 7·8 to 8·2 log10 CFU ml(-1) depending on the strain, and at least 50% of the P. freudenreichii population displayed an intact envelope. As lysis of part of a bacterial population may be a microbial strategy to recover nutrients, in CIRM-BIA 138 (the strain with the highest population at day 11), cell lysis was assessed by quantifying intact bacterial cells using qPCR targeting the housekeeping gene tuf. No lysis was observed.
  
  
  CONCLUSIONS
  Taken together, our results suggest that P. freudenreichii strains use a viable but nonculturable state to adapt to the LTS phase.
  
  
  CONCLUSIONS
  Assessing the viability of P. freudenreichii and understanding their mechanisms for survival should be of great interest regarding their potential probiotic applications.
authors.affiliation: Department of General Biology, Federal University of Minas Gerais, Belo Horizonte, Minas Gerais, Brazil.|INRA, UMR 1253, Science et Technologie du Lait et de l'Oeuf, Rennes, France.|AGROCAMPUS OUEST, UMR1253, UMR Science et Technologie du Lait et de l'Oeuf, Rennes, France.
authors.forename: F F
authors.initials: FF
authors.lastname: Aburjaile
authors.affiliation: INRA, UMR 1253, Science et Technologie du Lait et de l'Oeuf, Rennes, France.|AGROCAMPUS OUEST, UMR1253, UMR Science et Technologie du Lait et de l'Oeuf, Rennes, France.
authors.forename: M-N
authors.initials: MN
authors.lastname: Madec
authors.affiliation: INRA, UMR 1253, Science et Technologie du Lait et de l'Oeuf, Rennes, France.|AGROCAMPUS OUEST, UMR1253, UMR Science et Technologie du Lait et de l'Oeuf, Rennes, France.
authors.forename: S
authors.initials: S
authors.lastname: Parayre
authors.affiliation: Department of General Biology, Federal University of Minas Gerais, Belo Horizonte, Minas Gerais, Brazil.
authors.forename: A
authors.initials: A
authors.lastname: Miyoshi
authors.affiliation: Department of General Biology, Federal University of Minas Gerais, Belo Horizonte, Minas Gerais, Brazil.
authors.forename: V
authors.initials: V
authors.lastname: Azevedo
authors.affiliation: INRA, UMR 1253, Science et Technologie du Lait et de l'Oeuf, Rennes, France.|AGROCAMPUS OUEST, UMR1253, UMR Science et Technologie du Lait et de l'Oeuf, Rennes, France.
authors.forename: Y
authors.initials: Y
authors.lastname: Le Loir
authors.affiliation: INRA, UMR 1253, Science et Technologie du Lait et de l'Oeuf, Rennes, France.|AGROCAMPUS OUEST, UMR1253, UMR Science et Technologie du Lait et de l'Oeuf, Rennes, France.
authors.forename: H
authors.initials: H
authors.lastname: Falentin
mesh_terms: D003470:Culture Media / Q000032:analysis / Q000378:metabolism*; D050296:Microbial Viability; D011424:Propionibacterium / Q000254:growth & development* / Q000378:metabolism
chemical_list: D003470:Culture Media
keywords: Propionibacterium freudenreichii; adaptation; bacteria; culturability; growth phases; long-term survival; viable but nonculturable