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Time-resolved genetic responses of Lactococcus lactis to a dairy environment

Authors

  • Herwig Bachmann,

    1. NIZO food research, P.O. Box 20, 6710 BA Ede, the Netherlands.
    2. Kluyver Centre for Genomics of Industrial Fermentation, Delft, the Netherlands.
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    • Present addresses: Vrije Universiteit Amsterdam, Systems Bioinformatics IBIVU, De Boelelaan 1085, Amsterdam, the Netherlands;

  • Leonie De Wilt,

    1. NIZO food research, P.O. Box 20, 6710 BA Ede, the Netherlands.
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    • Vrije Universiteit Amsterdam, Department of Medical Oncology, Amsterdam, the Netherlands.

  • Michiel Kleerebezem,

    Corresponding author
    1. NIZO food research, P.O. Box 20, 6710 BA Ede, the Netherlands.
    2. Kluyver Centre for Genomics of Industrial Fermentation, Delft, the Netherlands.
    3. Wageningen University, Laboratory for Microbiology, Wageningen, the Netherlands.
      E-mail Michiel.Kleerebezem@nizo.nl; Tel. (+31) 318 659629; Fax (+31) 318 650400.
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  • Johan E. T. Van Hylckama Vlieg

    1. NIZO food research, P.O. Box 20, 6710 BA Ede, the Netherlands.
    2. Kluyver Centre for Genomics of Industrial Fermentation, Delft, the Netherlands.
    3. Danone Research, Gut and Microbiology Platform, R.D. 128, 91767 Palaiseau Cedex, France.
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E-mail Michiel.Kleerebezem@nizo.nl; Tel. (+31) 318 659629; Fax (+31) 318 650400.

Summary

Lactococcus lactis is one of main bacterial species found in mixed dairy starter cultures for the production of semi-hard cheese. Despite the appreciation that mixed cultures are essential for the eventual properties of the manufactured cheese the vast majority of studies on L. lactis were carried out in laboratory media with a pure culture. In this study we applied an advanced recombinant in vivo expression technology (R-IVET) assay in combination with a high-throughput cheese-manufacturing protocol for the identification and subsequent validation of promoter sequences specifically induced during the manufacturing and ripening of cheese. The system allowed gene expression measurements in an undisturbed product environment without the use of antibiotics and in combination with a mixed strain starter culture. The utilization of bacterial luciferase as reporter enabled the real-time monitoring of gene expression in cheese for up to 200 h after the cheese-manufacturing process was initiated. The results revealed a number of genes that were clearly induced in cheese such as cysD, bcaP, dppA, hisC, gltA, rpsE, purL, amtB as well as a number of hypothetical genes, pseudogenes and notably genetic elements located on the non-coding strand of annotated open reading frames. Furthermore genes that are likely to be involved in interactions with bacteria used in the mixed strain starter culture were identified.

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