Fig. 2
From: Identifying biases and their potential solutions in human microbiome studies
Microbiome data is compositional and does not represent absolute counts. As a consequence of the arbitrary total amount of sequencing reads a DNA sequencing platform can generate, the resulting data is compositional. This means that one DNA sequence does not correspond to one cellular unit, and an increase in relative abundance from one group can result in the decrease of relative abundance of another. This can occur even when the absolute abundance of a group does not change