International Centre for Theoretical Physics (ICTP), Italy
A macroecological description of gut microbial community dynamics
The most fundamental questions in microbial ecology concern the diversity and variability of communities. Their composition varies widely across space and time, as it is determined by a non-trivial combination of stochastic and deterministic processes. The interplay between non-linear community dynamics and environmental fluctuations determines the rich statistical structure of community variability, with both rapid temporal dynamics fluctuations and non-trivial correlations across habitats. Host-associated microbial communities, ike communties inhabiting the human gut, have a widely recognized importance for host health, and a better understanding of their dynamics is crucial to improve our diagnostic capacity and to design therapies. In this work, we analyse long time-series of gut microbiome and compare intra- and inter-community dissimilarity. Under a macroecological framework we characterise their statistical properties. We show that most taxa have large but stationary fluctuations over time, while a minority is characterised by quick changes of average abundance which cluster in time, suggesting the presence of alternative stable states. We disentangle inter-individual variability in a major stochastic component and a deterministic one, the latter recapitulated by differences in the carrying capacities of taxa. Finally, we develop a model which includes environmental fluctuations and alternative stable states. This model quantitatively predicts the statistical properties of both intra- and inter-individual community variability, therefore summarising variation in a unique macroecological framework.