Sampling timeline and potential enteric microbiome biomarkers of acute GVHD. Sampling timeline (top). Microbiome samples were collected at 3 timepoints during the transplant course: before conditioning regimen (T0), during aplasia (T1), and after engraftment (T2). Focus on T1, showing details of the microbiome markers associated with the development of acute GVHD (bottom). In particular, low bacterial α-diversity, quantified by Shannon index, relative dominance by Enteococcaceae and Staphylococcaceae, and relative loss of Lachnospiraceae were correlated to acute GVHD, its severity, and organ localization. aGVHD, acute graft-versus-host disease.