Fig. 2. Frequencies of reads coding ribosomal protein genes and other widely conserved single-copy genes in unassembled short-read shotgun metagenomes.

Each panel indicates one metagenomic sample, and each dot in a panel represents the RPKM of one ortholog (i.e., the number of reads normalized by the length of that ortholog and sequencing depth). Statistical significance (Brunner–Munzel test with Bonferroni’s correction) is shown at the top of each panel. Panels A–E, F–H, and I–K are the results from human gut metagenomes, seawater metagenomes, and soil metagenomes, respectively. N.S. not significant, Ribo ribosomal protein genes.