Growth phase-associated changes in the proteome and transcriptome of Lactobacillus rhamnosus GG in industrial-type whey medium.

Summary The growth phase during which probiotic bacteria are harvested and consumed can strongly influence their performance as health-promoting agents. In this study, global transcriptomic and proteomic changes were studied in the widely used probiotic Lactobacil- lus rhamnosus GG during growth in industrial-type whey medium under strictly defined bioreactor con- ditions. The expression of 636 genes (P 0.01) and 116 proteins (P < 0.05) changed significantly over time. Of the significantly differentially produced proteins, 61 were associated with alterations at the transcript level. The most remarkable growth phase- dependent changes occurred during the transition from the exponential to the stationary growth phase and were associated with the shift from glucose fer- mentation to galactose utilization and the transition from homolactic to mixed acid fermentation. Further- more, several genes encoding proteins proposed to promote the survival and persistence of L. rhamno- sus GG in the host and proteins that directly contrib- ute to human health showed temporal changes in expression. Our results suggest that L. rhamnosus GG has a highly flexible and adaptable metabolism and that the growth stage during which bacterial cells