#FEMSmicroBlog: Our first microbes


The first microbes that humans encounter are likely the ones that we swallow on our way through the birth channel. Thereafter, we are exposed to microbes from a multitude of sources. But not all of these microbes end up as part of our gut microbiota. This would require them to have what it takes to survive and multiply under the conditions offered. The review “Settlers of our inner surface – Factors shaping the gut microbiota from birth to toddlerhood” in FEMS Microbiology Reviews describes and discusses what happens to the human microbiota during our first years of life, and why some microbes are more likely to be found in our gut than others. The senior author of the review, Tine Rask Licht, explains more on #FEMSmicroBlog. #FascinatingMicrobes 


Tiny settlers

We can think of bacteria as ‘settlers’ – newcomers to an unpopulated environment. Like the historical human settlers of an unknown land, bacteria first arrive at a new destination. Then they need to find a spot that offers resources and conditions that allow them to live and prosper. Finally, what it takes for them to populate a new environment is their ability to compete for resources under the given conditions.

Starting from this perspective, our review “Settlers of our inner surface – Factors shaping the gut microbiota from birth to toddlerhood” in FEMS Microbiology Reviews discusses where our intestinal bacteria come from, what they need to survive and multiply, and how competition influences the composition of the microbiota from birth to toddlerhood.

Influence of selected factors on the developing microbiota. For more details, see the review by Laursen et al.


An important window of opportunity

The process that the intestinal microbial community undergoes during the first three years of life is very unlike anything that happens in this ecosystem at any other time of our life. The number of bacteria increases from a few up to 1012 per gram, and at the same time, the species diversity increases drastically.

The first years of life are considered a highly important developmental window because the infant gut microbiota is less resilient and more responsive to external and environmental factors than the established bacterial community of the adult gut. In the review, we discuss the external and environmental factors that affect microbial exposure and bacterial growth physiology. These factors shape the microbial ecosystem and the temporal succession of bacterial establishment, which we view as a fundament for understanding the role of gut bacteria in host health.


In the first years of life, the gut microbiota is less resilient and more responsive to external and environmental factors than the one in the adult gut.


The perspective of a microbe

Many excellent reviews and experimental reports previously addressed how the gut microbiota affects human health. The current review takes the perspective of the bacteria and asks how the conditions within the human host govern the development of the bacterial community. To understand this, it is necessary to bring long-established knowledge from the scientific fields of culture-based microbiology and systems ecology into play.


About the author of this blog

Tine Rask Licht is professor and head of the Research Group on Gut, Microbes and Health at the National Food Institute, Technical University of Denmark. She holds an MSc in Microbiology, and a PhD in Molecular Microbial Ecology. Today, her group focuses on the effects of diet on the intestinal bacterial community, which they study in humans, animal models, and in vitro model systems. The research group has contributed significantly to the understanding of the role of diet on the establishment of the microbiota in young infants. From 2012 to 2018, Prof. Licht was heading the research centre ‘Gut, Grain and Greens’, and she is currently heading the major research effort ‘PRIMA’ – towards Personalized dietary Recommendations based on the Interaction between diet, Microbiome and Abiotic conditions in the gut, recently funded by the Novo Nordisk Foundation. She is chair of the panel of Global Grants for Gut Health, supported by Yakult and Nature Research.

About this blog section

The section #FascinatingMicrobes for the #FEMSmicroBlog explains the science behind a paper and highlights the significance and broader context of a recent finding. One of the main goals is to share the fascinating spectrum of microbes across all fields of microbiology.

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