Thorough understanding of the initial colonization process of human intestines is important to optimize the prevention of microbiota-associated diseases, and also to further improve the current microbial therapies. In recent years, therefore, colonization of the human gut has gained renewed interest. However, due to a lack of standardization of life events that might influence this early colonization process in humans, many generally accepted insights are based on deduction and assumption. In our review, we compare knowledge on colonization in humans with research in piglets, because the intestinal tract of pigs is remarkably similar to that of humans and the early-life events are more standardized. We assess potential similarities and challenge some concepts that have been widely accepted in human microbiota research. Bacterial colonization of the human gut is characterized by successive waves in a progressive process, to a complex gut microbiota community. After re-analyzing available data from piglets, we found that the bacterial colonization process is very similar in terms of the wave sequence and functionality of each wave. Moreover, based on the piglet data, we found that, in addition to external factors such as suckling and nutrition, the bacterial community itself appears to have a major influence on the colonization success of additional bacteria in the intestine. Thus, the colonization process in piglets might rely, at least in part, on niche dependency, an ecological principle to be considered in the intestinal colonization process in humans.
Keywords: gut microbiota; human; intestinal colonization; niche dependency; pig.