Mice Study: Probiotics Do Not Alter Gut Microbiota Makeup

But, probiotics induce marked changes in bacterial metabolic pathways in mice, humans

THURSDAY, Oct. 27 (HealthDay News) -- Consumption of a commercially available probiotic fermented milk product (FMP) does not induce significant changes in gut microbiota composition in human and gnotobiotic mice, but does induce changes in bacterial metabolic pathways, according to an experimental study published online Oct. 26 in Science Translational Medicine.

Nathan P. McNulty, from the Washington University School of Medicine in St. Louis, and colleagues investigated how probiotic bacterial strains affect gut microbiota in human and mice models. Fecal microbiomes and metatranscriptomes were characterized in adult female monozygotic twin pairs at four weeks prior, seven weeks during, and four weeks after twice-daily consumption of a FMP containing Bifidobacterium animalis subspecies lactis, two strains of Lactobacillus delbrueckii subspecies bulgaricus, Lactococcus lactis subspecies cremoris, and Streptococcus thermophilus. Gnotobiotic mice, which have a 15-species model human gut microbiota, were investigated before and after gavage with all five FMP strains.

The investigators observed no significant changes in the human fecal bacterial composition or in the proportional representation of genes encoding known enzymes, whereas microbiota configuration in mice changed minimally after single or repeated FMP gavage. Fecal RNA-Seq analysis and mass spectrometry of urinary metabolites in mice after FMP gavage revealed significant changes in expression of microbiome-encoded enzymes related to metabolism, most prominently carbohydrate metabolism. There were significant changes seen in the human fecal metatranscriptome during the period of FMP consumption.

"These experiments illustrate a translational research pipeline for characterizing the effects of FMPs on the human gut microbiome," the authors write.

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