Gene

Ecology

Bacteria

Biology

Ecological succession

Evolutionary biology

Genetics

Microbiome

Human disease

Bioinformatics

Human microbiome

Microbial population biology

Zoology

Colonization

Nature Reviews Microbiology

Associations between age and the human microbiota are robust and reproducible. The microbial composition at several body sites can predict human chronological age relatively accurately. Although it is largely unknown why specific microorganisms are more abundant at certain ages, human microbiota research has elucidated a series of microbial community transformations that occur between birth and death. In this Review, we explore microbial succession in the healthy human microbiota from the cradle to the grave. We discuss the stages from primary succession at birth, to disruptions by disease or antibiotic use, to microbial expansion at death. We address how these successions differ by body site and by domain (bacteria, fungi or viruses). We also review experimental tools that microbiota researchers use to conduct this work. Finally, we discuss future directions for studying the microbiota’s relationship with age, including designing consistent, well-powered, longitudinal studies, performing robust statistical analyses and improving characterization of non-bacterial microorganisms. The human microbiota can undergo dramatic changes during different phases of life (for example, during colonization after birth, after disturbances or in old age). In this Review, Knight and colleagues discuss the microbiota successions that occur from the cradle to the grave.

Microbiota succession throughout life from the cradle to the grave