Effect of maternal miRNAs and milk oligosaccharides on regulating the growth behavior of Bifidobacterium longum subsp. infantis

The interplay between maternal microRNAs (miRNAs) and human milk oligosaccharides (HMOs) in influencing infant gut bacteria remains poorly understood. This study investigated how milk miRNAs impact the growth dynamics and gene expression of Bifidobacterium infantis cultured on HMOs and lactose as substrates (1 % w / v ). The strain was cultured in vitro with either human milk miRNAs or synthetic mimics (500 ng/mL). B. infantis grew significantly faster on HMOs (plateau at 11.23 h) than lactose (12.75 h), but miRNAs showed minimal effects on growth in both substrates. Transcriptome analysis further showed limited differential gene expression upon miRNA treatments, with only 11 overexpressed genes in the HMO-miRNA group, none likely affecting metabolism. In contrast, substrate type drove expression changes in 1986 genes, involving in ABC transporters, amino acid biosynthesis, purine, and carbohydrate metabolism. This research highlighted the stronger effects of HMOs than miRNAs on B. infantis biology, despite both being abundant in milk. • Effect of milk miRNAs on the growth profiles of B. infantis was evaluated. • miRNAs at 500 ng/mL showed limited effects on growth and gene regulation of B. infantis . • B. infantis utilized HMOs more efficiently than the disaccharide lactose. • HMOs triggered differential expression of 1986 genes compared to lactose.