Patterns of gut microbiome composition, function and dynamics in young children, adolescents and adults over a three-year period

Despite their relevance, studies of the long-term stability of the gut microbiome are rare due to the difficulty in following the same individual through long periods of time, particularly during childhood and adolescence. Here, we have been able to analyze microbiome stability throughout a 3-year period in young children, adolescents, and adults of the same population, at the levels of taxonomic composition and functional profile. Our analyses show that stability is lower at taxonomical than at functional level in all three age groups, indicating the existence of functional redundancy through time. Considering the entire period of sampling, young children were significantly more unstable than the other two groups at the level of taxonomic composition. However, local analyses revealed that low stability for both composition and function was restricted to the time period between 20 and 24 months of age, whereas after this point stability levels in young children were similar to those of adolescents and adults. Although the microbiome stabilized at around two years of age in terms of large-scale, rapid changes in diversity, composition, and functional profile, further changes did occur both before and after adolescence. Therefore, adolescence remains a transitional period, in which the abundances of some taxa and functions still differ from adult levels. These include, among others, Bifidobacterium, Streptococcus, Bacteroides fragilis and several Lachnospiraceae, as well as various functions related to energy metabolism.