Figure 1.

The evolution of the upper respiratory tract microbiota during aging. The oral and nasal microbiome at birth and infancy is influenced by environmental exposures, including breastfeeding. The nasal and oral tissue sites provide unique niches for bacteria to grow and evolve, but by late age the nasal and oral microbiome become quite similar, revealing potential breakdown of important host mechanisms in microbiota community composition. This is highlighted by increased α‐diversity (or microbial diversity within a host) during aging, indicating lack of community regulation.