Characteristics of the adult nasopharyngeal microbiome at baseline. Each volunteer is represented by a branch of the circular hierarchical clustering tree. From inside out, at baseline, five distinct adult nasopharyngeal microbiome profiles were identified from the individual nasopharyngeal bacterial communities, appointed A to E (I). The individual microbiome compositions are proportionally displayed at genus level (II). Natural pneumococcal carriers are marked in green, experimentally colonized volunteers in red, and those without pneumococcal acquisition are depicted in grey (III). The length of the blue bars displays the diversity of the microbiome at baseline (IV). This figure was generated using iTOL .