Erik Orberg, MD, PhD, University Hospital of the Technical University of Munich, Munich, Germany, provides an overview of findings from a longitudinal analysis of intestinal bacterial, viral and fungal populations in patients undergoing allogeneic stem cell transplantation. Bacterial and viral diversity were reduced in patients post-transplant, but fungal diversity was constant. Patients with graft-versus-host disease (GvHD) additionally had an increased loss of microbial diversity. Metabolite levels were also significantly affected post-transplant, and systemic antibiotic therapy was revealed to affect metabolite production and microbiome function. This interview took place at the 63rd ASH Annual Meeting and Exposition congress in Atlanta, GA.