Fig. 1.

Identification of age-discriminatory viral contigs. (A) Random Forests was used for a regression analysis to test if relative abundance of viral contigs is a good predictor of the human fecal microbiota donor’s chronologic age. The dataset of assembled contigs from all viromes sampled from twin pairs was filtered to remove family-specific contigs (SI Methods). The percentage variation explained by the regression in 100 independent runs of the Random Forests algorithm was 54.5 ± 3.1% (mean ± SD). Predicted age (mean ± SD) for each fecal virome sample is plotted against the donor’s chronologic age. Most errors in classification occur in samples obtained from donors <6 mo (red) and >23 mo of age (blue). Green diamonds indicate predicted age when using a sparse set of 22 of the most discriminatory contigs shown in B. The black diagonal represents the identity line (y = x). (B) Heat map of the abundance distribution of significantly discriminatory contigs as a function of age (months). Each row represents a significant age-associated viral contig. Boxes on the right are colored according to the contig’s taxonomic annotation.