Infant gut microbiomes exhibit circadian rhythms that can be detected as early as 2 weeks after birth and become more pronounced with age, according to a study published in the journal Cell Host & Microbe. Diet was found to have less of an impact on microbiome development than previously believed, with age playing a more significant role in the composition of the infant microbiome. Researchers from the Technical University of Munich conducted a randomized controlled trial comparing microbiome development in breastfed infants and those who received different types of formula.
The study included 210 infants who were sampled at various ages up to 24 months to track changes in their microbiomes. While diet did not have a significant impact on microbiome development, differences were observed in the gut metabolite profiles of breastfed and formula-fed infants. Breast milk was found to have a more significant effect on the infant metabolism in the gut, potentially leading to downstream effects on health.
It was also discovered that infant gut microbiome species exhibit 24-hour fluctuations in abundance, even when grown in a lab setting without external light or host cues. This suggests that bacteria have intrinsic mechanisms that allow them to adapt to a day and night cycle, potentially giving them an advantage in colonizing the human intestine. Further research will investigate whether individual bacterial species maintain these rhythms when grown in isolation and identify the genes that control these circadian behaviors.
The study found that GOS-supplemented infant formula was more effective at promoting sustained levels of Bifidobacteria compared to formula containing only Bifidobacteria. However, overall gut microbe diversity increased gradually in all infants over time, with no significant differences observed among the various diet groups by 24 months. The results suggest that the infant intestinal system is flexible in adapting to different dietary environments. The observation of circadian rhythms in infant microbiomes is the first evidence that bacteria maintain these rhythms independently of external cues.
The researchers plan to delve deeper into the mechanisms by which bacteria control their circadian behaviors in future studies. By understanding these mechanisms, they hope to gain insight into how to manipulate microbiome circadian rhythms for potential therapeutic interventions. The study highlights the importance of age and breast milk in shaping the infant gut microbiome and provides new insights into the role of circadian rhythms in bacterial colonization of the human intestine.
