The conceptual framework of a dynamic core microbiome in extreme conditions.

OTU a-i represent the units of interest defined at a given taxonomic level. Subject A and B represent time series communities to be compared using the OTU table. The presences of OTUs are represented by the symbols “•”. The OTUs present at all time points of all subjects are designated as common taxa (OTU e). Those present in all subjects but not at all time points are designated as potential common taxa (OTU f-i). Both taxa (common taxa and potential common taxa) can be recognized as core microbiomes from time series data.