Holobiont Development: Embryology and Ecological Succession

Developmental biology has expanded to include prenatal and postnatal environmental factors as agents in producing phenotypes. Environmental agents can alter gene expression patterns and channel development into particular trajectories. Prenatal environments (e.g., diet, stress) can induce gene expression patterns that change metabolism in ways that can promote the survival of the offspring born into that particular environment. In addition to abiotic environmental agents, symbiotic microbes are necessary for the completion of mammalian development and have been shown to be critical for the proper development of the immune system and nervous system. The symbiotic microbes become organized into ecosystems within the body, especially in the gut, and the appreciation that organisms develop as conjoined ecosystems has important implications for biology, psychology, medicine, and public health. Indeed, microbial symbionts are necessary for the development of numerous cognitive and social behaviors in mice, and probably also in humans.