Mother-to-infant plasmid transmission in early postpartum and its association with dominant gut bacteria

BackgroundThe gut microbiome plays a crucial role in human health, and it is known that the microbiome is transmitted from mother to infant at birth and has profound effects on an individuals health. Although extensive research has been conducted on mother-to-infant microbiome transmission, little is known about plasmid transmission and its effects on the infant microbiome. Plasmids are considered important contributors to early development of the gut microbiome due to their functions, such as antibiotic resistance, and their ability to be transferred between a wide range of host bacteria. MethodsIn this study, we assembled plasmid sequences from longitudinal fecal data of 65 mother-infant pairs and analyzed plasmid sharing between mothers and infants during the first year of life. After identifying shared plasmids, we investigated the relationship between plasmid sharing and delivery mode. We also characterized the functions and host range of shared plasmids. ResultsWe found that the number of plasmids was lower in infants than in mothers, probably reflecting the lower overall diversity of the infant microbiome. Additionally, we detected shared plasmids between mothers and infants, marking the first discovery of mother-to-infant plasmid transmission. Our findings revealed that plasmids are more likely to be transmitted from mother to infant immediately after birth, with the likelihood of transmission decreasing as infants age. This underscores the critical role of the maternal microbiome in shaping early development of the gut microbiome. Moreover, plasmids from dominant bacteria in mother-to-infant microbiome transmission, such as Bacteroides, were frequently transmitted to infants and carried specific functional traits. In particular, plasmid genes such as mbpA, mbpB, and mbpC were frequently shared between mothers and infants. Each of these genes encodes a protein of a specific size and plays an important role in plasmid mobilization, or the transfer of plasmids to other bacteria. Plasmids improve the fitness and environmental adaptability of host bacteria, which may contribute to the development of a healthy gut microbiome in infants. ConclusionsThis study revealed that mother-to-infant plasmid transmission likely occurs during the early postpartum period and is influenced by dominant gut bacteria. These findings provide new insights into the mothers role in shaping the infants gut microbiome development.