What is already known
Infants acquire their gut microbiotas during birth and in the first weeks of life through breastfeeding. This period is critical for cognitive and immune system development, which are promoted by gut microbes through the production of microbial metabolites. However, it’s unclear how an infant’s gut microbiota develops together with its metabolome — the set of small molecules that microbes produce.
What this research adds
Researchers tracked the development of gut microbiotas and metabolomes from late pregnancy to one year of age using data from a group of 70 mothers and their infants. Although the gut metabolomes of infants were less diverse than those of their mothers, the researchers identified more than 2,500 metabolites unique to the infant microbiotas. The team also discovered that some microbial genes, in particular those associated with diet, were transferred from a mother’s microbiota to her infant’s microbiota.
Conclusions
The findings suggest that a mother’s microbiota may shape the infant gut microbiota through horizontal gene transfer, in addition to the classical transmission of maternal bacteria to the infant’s gut.
It’s known that infants acquire their gut microbiotas during birth and in the first weeks of life through breastfeeding. Now, researchers have found that a mother’s gut microbes share genes with bacteria in the infant gut both before and after birth.
The findings, published in Cell, suggest that a mother’s microbiota may shape the infant gut microbiota through horizontal gene transfer, in addition to the classical transmission of maternal bacteria to the infant’s gut. “This is the first study to describe the transfer of mobile genetic elements between maternal and infant microbiomes,” says senior study author Ramnik Xavier at Massachusetts General Hospital.
The period that spans late pregnancy and the first year of life is critical for cognitive and immune system development, which are promoted by gut microbes through the production of microbial metabolites. However, it’s unclear how an infant’s gut microbiota develops together with the metabolome — the set of small molecules that microbes produce.
To address this question, Xavier and his colleagues tracked the development of gut microbiotas and metabolomes from late pregnancy to one year of age using data from a group of 70 mothers and their infants.
Unique metabolites
In infants, the levels of Streptococcus thermophilus and Lactobacillus acidophilus increased around birth, whereas Anaerotruncus colihominis, which is thought to modulate immune responses, was reduced. Some species, including Streptococcus salivarius and Streptococcus parasanguinis, were frequently found during pregnancy but not after birth.
Although the gut metabolomes of infants were less diverse than those of their mothers, the team identified more than 2,500 metabolites unique to the infant microbiota. The metabolites included neurotransmitters and immune modulators, and many were modified from breastmilk substrates by gut bacteria.
“Many of these metabolites likely impact immune system and cognitive development,” says study co-first author Tommi Vatanen.
Influencing microbiotas
The researchers also discovered that some microbial genes, in particular those associated with diet, were transferred from a mother’s microbiota to her infant’s microbiota. Some types bacteriophages, or viruses that infect bacteria, likely contributed to the exchange of genes between maternal and infant microbiotas.
This transfer of genes started immediately before birth and extended throughout the first few weeks after birth, and it allowed maternal gut bacteria to influence the composition and function of the infant gut microbiotas. Indeed, the metabolomes and immune-molecule signatures of infants who received regular formula were distinct from those of breastfed infants, the researchers found.
The study offers insights into the of gut colonization dynamics that influence infant development during late pregnancy and early life, the researchers say.
