title: Degradation of 16S rRNA and attributes of viability of viable but nonculturable probiotic bacteria.
abstract: OBJECTIVE
  To assess the stability of 16S rRNA of viable but nonculturable (VBNC) probiotics during storage when compared with different attributes of viability.
  
  
  RESULTS
  Levels of RNA of the probiotic strains Bifidobacterium longum 46, B. longum 2C and B. animalis subsp. lactis Bb-12 were monitored during storage in fermented and nonfermented foods. Cells which gradually lost their culturability in fermented products retained high level of rRNA, whereas rRNA of acid-killed control cells decreased at faster rate. Furthermore, the viability of B. longum 2C was monitored during storage by measuring changes in reductase activity, cytoplasmic membrane integrity and esterase activity using a flow cytometer. All of the culture-independent viability assays suggested that the cells remained viable during storage. In nonfermented media, the observed losses in culturability were smaller, and the changes in cell counts were comparable with the changes in rRNA levels.
  
  
  CONCLUSIONS
  Viable but nonculturable probiotics maintain high levels of rRNA and retain properties of viable bacteria including reductase activity. Quantification of 16S rRNA complements culture-independent viability assays.
  
  
  CONCLUSIONS
  Culture-independent viability assays allow the detection of VBNC probiotics, and can be used parallel to conventional culture-dependent methods to obtain accurate information on probiotic viability.
authors.affiliation: Functional Foods Forum, University of Turku, Finland. sajola@utu.fi
authors.forename: S J
authors.initials: SJ
authors.lastname: Lahtinen
authors.forename: H
authors.initials: H
authors.lastname: Ahokoski
authors.forename: J P
authors.initials: JP
authors.lastname: Reinikainen
authors.forename: M
authors.initials: M
authors.lastname: Gueimonde
authors.forename: J
authors.initials: J
authors.lastname: Nurmi
authors.forename: A C
authors.initials: AC
authors.lastname: Ouwehand
authors.forename: S J
authors.initials: SJ
authors.lastname: Salminen
mesh_terms: D001644:Bifidobacterium / Q000166:cytology* / Q000235:genetics* / Q000254:growth & development; D015169:Colony Count, Microbial; D043302:Cultured Milk Products / Q000382:microbiology; D005511:Food Handling; D005516:Food Microbiology; D050296:Microbial Viability; D019936:Probiotics; D012329:RNA, Bacterial / Q000378:metabolism; D012336:RNA, Ribosomal, 16S / Q000378:metabolism*; D013997:Time Factors
chemical_list: D012329:RNA, Bacterial; D012336:RNA, Ribosomal, 16S