Impact of Pomegranate on Probiotic Growth, Viability, Transcriptome and Metabolism

Despite rising interest in understanding intestinal bacterial survival in situ, relatively little attention has been devoted to deciphering the interaction between bacteria and functional food ingredients. Here, we examined the interplay between diverse beneficial <i>Lactobacillaceae</i> species and a pomegranate (POM) extract and determined the impact of this functional ingredient on bacterial growth, cell survival, transcription and target metabolite genesis. Three commercially available probiotic strains (<i>Lactobacillus acidophilus</i> NCFM, <i>Lacticaseibacillus rhamnosus</i> GG and <i>Lactiplantibacillus plantarum</i> Lp-115) were used in growth assays and flow cytometry analysis, indicating differential responses to the presence of POM extract across the three strains. The inclusion of POM extract in the growth medium had the greatest impact on <i>L. acidophilus</i> cell counts. LIVE/DEAD staining determined significantly fewer dead cells when <i>L. acidophilus</i> was grown with POM extract compared to the control with no POM (1.23% versus 7.23%). Whole-transcriptome analysis following exposure to POM extract showed markedly different global transcriptome responses, with 15.88% of the <i>L. acidophilus</i> transcriptome, 19.32% of the <i>L. rhamnosus</i> transcriptome and only 2.37% of the <i>L. plantarum</i> transcriptome differentially expressed. We also noted strain-dependent metabolite concentrations in the medium with POM extract compared to the control medium for punicalagin, ellagic acid and gallic acid. Overall, the results show that POM extract triggers species-specific responses by probiotic strains and substantiates the rising interest in using POM as a prebiotic compound.