Fig. 1.

Multiple stable compositional states in the developing gut microbiota of the premature infant. (A) Relative abundance of the 20 most dominant bacterial taxa in 15 fecal samples collected between days 5 and 21. Sequences were classified to the highest taxonomic level to which they could be confidently assigned. Dots indicate metagenomic survey dates. Relevant clinical features are shown along the x axis. (B) Principal coordinates analysis of unweighted UniFrac distances between fecal microbiotas shown in A and those from recently published surveys of adults (3, 5, 47), term infants (5), and preterm infants (17, 19), and from a survey of gut microbes from premature infants in a companion study (Fig. S8). Each circle corresponds to a collection of 16S rRNA gene sequences colored according to study. Samples from this work (black circles) are labeled by day. The percentage of variation explained by the plotted principal coordinates is indicated on the axes. Large-scale alterations in the infant's gut microbiota composition occurred around days 9 and 15.