Average genome size reflects diverse modes of functional adaptation in the gut microbiome. (A) Barplot of AGS for stool metagenomes. (B) Log2 fold change of KOs across stool metagenomes. KOs were grouped according to the BRITE functional hierarchy. Only KOs that were significantly correlated with AGS (q < 1e-3) are displayed. (C) Log2 fold change of essential single-copy KOs across stool metagenomes.