Allo-HCT patients with GI GVHD developed microbial disruption postonset GVHD. (A-D) Volcano plot [−log10(FDR P value) vs log2(fold change)] representation of microbial dysbiosis of postonset GVHD (day 0 to +20 relative to onset) and no-GVHD (day −3 to +102 relative to allo-HCT) fecal samples. Plot includes taxa with mean abundance within samples >0.1% and highlights the 20 genera with strongest FDR corrected P-value significance (≤0.05). (A-B) No-GVHD compared with UGI and LGI patients had increased abundance of class Clostridia commensals Coprococcus and Blautia, respectively, post-GVHD onset. (C-D) Non-GI and UGI patients also had increased relative abundance of Blautia and Erysipelatoclostridium when compared with LGI patients. f, family; g, genus; p, phylum; Proteo, Proteobacteria.