Table 1_Patterns of gut microbiome composition, function and dynamics in toddlers, adolescents and adults over a three-year period.xlsx

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 toddlers, 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, toddlers 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 toddlers 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 members of the Lachnospiraceae, as well as various functions related to energy metabolism. Overall, our results pinpoint the two-years mark as a point of significant stabilization for the gut microbiome, without precluding the further occurrence of important changes in the relative abundance of specific taxa and gene functions both before and after adolescence.

尽管肠道微生物组（gut microbiome）的长期稳定性研究具有重要学术价值，但由于难以长期追踪同一受试者，尤其是在儿童期与青春期阶段，相关研究仍较为稀缺。本研究成功对同一人群中的幼儿、青少年及成人开展了为期3年的肠道微生物组稳定性分析，覆盖分类组成（taxonomic composition）与功能谱（functional profile）两个分析层面。分析结果显示，在三个年龄组中，肠道微生物组的分类层面稳定性均低于功能层面，这表明随着时间推移存在功能冗余（functional redundancy）现象。若考虑整个采样周期，幼儿组的分类组成稳定性显著低于另外两个年龄组。然而局部分析表明，分类组成与功能层面的低稳定性均集中在20至24月龄这一时间段，在此之后幼儿组的稳定性水平与青少年及成人组趋于一致。尽管从多样性、组成及功能谱的大规模快速变化维度来看，肠道微生物组在约2岁时趋于稳定，但在青春期前后仍会发生进一步的群落变化。因此，青春期仍是一个过渡阶段，部分微生物类群（taxa）及功能的相对丰度仍与成人水平存在差异，其中包括双歧杆菌属（Bifidobacterium）、链球菌属（Streptococcus）、脆弱拟杆菌（Bacteroides fragilis）及毛螺菌科（Lachnospiraceae）的多个成员，以及诸多与能量代谢相关的功能。总体而言，本研究结果表明，肠道微生物组在2岁左右会出现显著的稳定性提升，但并未排除青春期前后特定类群及基因功能的相对丰度仍会发生重要变化的可能性。