Methods Science Journalism

Development of gut bacteria

Text: Sarah Schoch, Salome Kurth; Translation: Lea Arigoni

Our body is colonised by trillions of bacteria that interact with our health. The great diversity of bacteria in our gut gradually builds up in the first years of life. In our research we investigate whether there is a connection between the growth of gut bacteria and the sleep-wake rhythm in early childhood. 

Our body is inhabited by at least as many bacteria (about 40 trillion) as we consist of human cells (1). Most of these bacteria are located in our gut, including over 1000 different species (2).

Gut bacteria contribute to our digestion, they can transform certain nutrients, such as cellulose (3), which we cannot digest, into other substances that we can then absorb. Interesting research in the last decade has also shown that gut bacteria influence our health. For example, gut bacteria have an impact on our immune system (4) and can protect us from other harmful bacteria (5).

Throughout life, gut bacteria undergo a process of development. 

At birth, the newborn is colonised with the mother’s bacteria. Various factors influence the intestinal bacteria composition, e.g. the way of birth (6) or the intake of antibiotics. Other factors are food and diet. Gut bacteria are different between infants who are breastfed and infants who drink breast milk substitutes (7). Also stopping breastfeeding changes the composition of gut bacteria, so that it stepwise resembles the composition of adults (8). Adults show greater species diversity, more bacterial stability and fewer differences between individuals compared to babies, see Figure 1 (9).

Dieses Bild hat ein leeres Alt-Attribut. Der Dateiname ist Entwicklung_DB_200604_pic-1-1024x576.jpg
Figure 1: The diversity and stability of gut bacteria is high in adults and low in children. The differences between infants are very large, whereas differences between adults are smaller. Adapted from (9).

Animal studies show that many of the intestinal bacteria undergo a daily rhythm (10). 

Through experiments that cause a disturbance of the internal clock (i.e. a kind of “jet lag”), it was possible to manipulate these rhythms of the intestinal bacteria. In particular, an effect was found when animals ate a high-fat and high-sugar diet (11). Another study shows that disrupting sleep causes changes not only in the composition of gut bacteria, but also in their activity (12). In adults, novel studies report a link between gut bacteria and diurnal rhythms (13). 

We are now exploring whether gut bacteria from babies are connected with the development of their sleep rhythm. This is an important piece of the puzzle to better understand the development of the sleep-wake cycle and to apply this knowledge to health promotion.

Photo by Derek Owens on Unsplash
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2. J. Qin et al., A human gut microbial gene catalogue established by metagenomic sequencing. Nature 464, 59-65 (2010).
3. M. Rajilic-Stojanovic, Function of the microbiota. Best Pract Res Clin Gastroenterol 27, 5-16 (2013).
4. T. Vatanen et al., Variation in Microbiome LPS Immunogenicity Contributes to Autoimmunity in Humans. Cell 165, 842-853 (2016).
5. C. M. Theriot et al., Antibiotic-induced shifts in the mouse gut microbiome and metabolome increase susceptibility to Clostridium difficile infection. Nat Commun 5, 3114 (2014).
6. M. G. Dominguez-Bello et al., Delivery mode shapes the acquisition and structure of the initial microbiota across multiple body habitats in newborns. Proc Natl Acad Sci U S A 107, 11971-11975 (2010).
7. H. J. Harmsen et al., Analysis of intestinal flora development in breast-fed and formula-fed infants by using molecular identification and detection methods. J Pediatr Gastroenterol Nutr 30, 61-67 (2000).
8. F. Backhed et al., Dynamics and Stabilization of the Human Gut Microbiome during the First Year of Life. Cell Host Microbe 17, 690-703 (2015).
9. E. S. Lim et al., Early life dynamics of the human gut virome and bacterial microbiome in infants. Nat Med 21, 1228-1234 (2015).
10. X. Liang, F. D. Bushman, G. A. FitzGerald, Rhythmicity of the intestinal microbiota is regulated by gender and the host circadian clock. Proc Natl Acad Sci U S A 112, 10479-10484 (2015).
11. R. M. Voigt et al., Circadian disorganization alters intestinal microbiota. PLoS One 9, e97500 (2014).
12. S. J. Bowers et al., Repeated sleep disruption in mice leads to persistent shifts in the fecal microbiome and metabolome. PLoS One 15, e0229001 (2020).
13. Y. Alvarez, L. G. Glotfelty, N. Blank, L. Dohnalova, C. A. Thaiss, The Microbiome as a Circadian Coordinator of Metabolism. Endocrinology 161, (2020).