Evolutionary change in the human gut microbiome: From a static to a dynamic view.

Our intestine is a melting pot of interactions between microbial and human cells. This gene-rich ecosystem modulates our health, but questions remain unanswered regarding its genetic structure, such as, "How rapid is evolutionary change in the human gut microbiome? How can its function be maintained?" Much research on the microbiome has characterized the species it contains. Yet the high growth rate and large population sizes of many species, and the mutation rate of most microbes (approximately 10-3 per genome per generation), could imply that evolution might be happening in our gut along our lifetime. In support of this view, Garud and colleagues present an analysis that begins to unravel the pattern of short- and long-term evolution of dozens of gut species. Even with limited longitudinal short-read sequence data, significant evolutionary dynamics-shaped by both positive and negative selection-can be detected on human microbiomes. This may only be the tip of the iceberg, as recent work on mice suggests, and its full extent should be revealed with dense time series long-read sequence data and new eco-evolutionary theory.