This episode features Dr. Joao Xavier PhD, a systems biologist from Memorial Sloan Kettering Cancer Center, speaking about the application of ecological principles and tools to individuals being treated for cancer. His lab combines multi-omics profiling with ecological models to generate insights on how microbes interact with each other, for application to clinical risk prediction and microbiota-focused interventions. He has studied individuals receiving bone marrow transplantation, who take antibiotics to prepare for treatment; the antibiotics cause significant gut microbiota shifts and the risk of bloodstream infections increases, so his lab is looking at whether the gut microbiota could mitigate this risk. Currently microbiome monitoring is not being used clinically in patients receiving cancer treatments, but a path exists for gaining the evidence needed to make this feasible and useful. Potentially, microbiome monitoring could allow physicians to move from reactive treatment with antibiotics to proactive intervention that prevents serious infections. Or the clinician could simulate potential treatment scenarios and figure out which one is the most beneficial. Probiotics could be administered to shape the microbiome – but rather than adding microorganisms that may simply be missing, these probiotics would be developed by thinking about the microbiome outcome and how to pressure the ecosystem in a certain direction. Episode abbreviations and links: Review in Nature Reviews Clinical Oncology, arguing for the relevance of microbiota management guided by ecological principles in cancer care: making the case for Ecological management of the microbiota in patients with cancer Mouse study investigating what may drive an increase in oral bacteria within the fecal microbiota and how it may link to patient outcomes: Oral bacteria relative abundance in faeces increases due to gut microbiota depletion and is linked with patient outcomes About Dr. Joao Xavier PhD: Joao B. Xavier, PhD, is a faculty member in the Program for Computational and Systems Biology at Memorial Sloan Kettering Cancer Center in New York. His lab combines experiments, computational modeling, and clinical data to study how the human microbiota influences cancer treatment outcomes. Dr. Xavier’s work has uncovered links between gut bacteria, immune recovery, and infection risk in patients undergoing intensive therapies such as allogeneic hematopoietic stem cell transplantation. He recently authored a Nature Reviews Clinical Oncology article (2025) proposing “ecological management” of the microbiota in oncology. This approach applies principles of ecosystem management to preserve beneficial microbes, minimize treatment-related damage, and guide precision interventions. He was awarded the 2026 ASM Microbiome Data Prize by the American Society for Microbiology in recognition of these contributions. His group collaborates broadly across clinical and basic sciences to develop microbiota-informed strategies that could improve responses to chemotherapy, immunotherapy, and infection control.