How to get and keep a microbiome

Abstract This chapter focuses on the ways that animal and plant hosts acquire microorganisms from the external environment and other hosts, including the mother. Hosts are challenged to facilitate the colonization of beneficial microorganisms while simultaneously deterring pathogens. In humans, birth indicates the transition from a microbe-free existence to a world filled with microorganisms, while diet and social contacts could promote or resist change in the gut microbiome, which had been regarded as unique as a fingerprint. The processes involved in retaining a microbiome are complex and involve host factors (including the immune system), among-microbe interactions (such as competition and mutualisms), and chance events that result in the loss or gain of particular microbial taxa.