Korean researchers uncover how beneficial maternal bacteria colonize newborn gut

Scientists have discovered why beneficial bacteria passed from mothers to their newborns can survive in the oxygen-rich environment of an infant's gut — the bacteria produce a kind of "energy shield" that protects them from oxidative stress.

The National Research Foundation of Korea said Wednesday that a research team led by Oh Sung-hwan, a professor at Harvard Medical School, had identified the mechanism by which Bacteroides fragilis, a key gut symbiont, uses a specific glycolipid to overcome the oxygen-rich conditions of a newborn's intestine and establish colonization.

Gut microbes are transmitted from mother to infant around the time of birth, forming the foundation of the baby's early intestinal ecosystem. Unlike in adults, however, oxygen is temporarily present in a newborn's gut — a formidable barrier for beneficial bacteria that are highly sensitive to oxygen.

The research team focused on the fact that Bacteroides fragilis colonizes the infant gut more rapidly in the early days after birth than other intestinal bacteria. Analysis showed that when exposed to oxygen, the bacterium significantly increases output of a cell-membrane glycolipid called alpha-galactosylceramide, or BfaGC.

BfaGC acts as an energy shield by tightly wrapping the cell membrane and preventing the bacterium's internal energy from leaking out. This allows the symbiont to conserve energy and survive even under oxidative stress.

Strains engineered to be unable to produce BfaGC showed a marked reduction in their ability to colonize the infant gut during transmission from mother to newborn.

BfaGC's role extended beyond the survival of beneficial bacteria. The glycolipid was also found to directly stimulate the development of immune cells in the newborn gut, supporting microbial colonization and the formation of the host's immune system at the same time.

The research is significant for having elucidated at the molecular level how maternal gut symbionts are transmitted to newborns and establish themselves in the early intestine. It is expected to provide clues for understanding the interplay between early-life microbiome formation and immune system development.

"This is basic research, but in the long term it could lay the groundwork for developing strategies to regulate maternal gut microbes or microbial metabolism so that beneficial bacteria are transmitted and established more effectively in infants," Oh said. "We hope it will advance into a new intervention that helps build a healthy early-life microbiome."

The findings, supported by the Ministry of Science and ICT and the National Research Foundation of Korea's Sejong Science Fellowship, were published online in the international journal Cell on Sept. 1.