Effect of maternal microRNA and HMOs on Bifidobacterium infantis

The interplay between maternal microRNAs (miRNAs) and human milk oligosaccharides (HMOs) in influencing infant gut microbiota development, especially the effect on the growth and behavior of beneficial species, remains poorly understood. In this study, we investigated how human milk-derived miRNAs impact the growth dynamics and gene expression of B. infantis ATCC 15697 cultured on HMOs and lactose as substrates. The growth kinetics and transcriptional responses of the bacteria were assessed when cultured in vitro using pooled HMOs and either diverse miRNAs from human donors or synthetic mimics. Our findings revealed that, although HMOs significantly promoted the growth speed of the organism compared to lactose, the addition of miRNAs had marginal effects on growth profiles. Transcriptome analysis further showed limited differential gene expression upon miRNA treatments, with minor changes involving genes unrelated to substrate utilization functions. In contrast, substrate type emerged as the primary driver of extensive transcriptional differences, notably in the enriched pathways critical for HMOs-specific metabolism, such as ABC transporters, biosynthesis of amino acids and cofactors, as well as purine and carbohydrate metabolism.