Certain cancers of the blood are treated by transplanting stem cells that can regenerate all kinds of blood cells from healthy donors. Even though this procedure has the potential to cure the cancer, common complications such as bloodstream infections or graft-versus-host disease (when the body rejects the donor cells) can lead to major side effects and even death. There is substantial evidence that these complications are linked to the microbes residing in the gut, collectively termed the gut microbiome, but the exact mechanism for this interaction is unknown. To address this knowledge gap, Dr. Wirbel will study how the genomes of gut microbes change over time in a large cohort of blood stem cell transplantation patients, using modern DNA sequencing techniques and developing novel analyses pipelines. He will then investigate whether the genes that are changing in microbial genomes might influence the human immune system and thereby contribute to these clinical complications.

Dr. Wirbel plans to develop a computational tool for the reference-free analysis of microbial genomes over time based on long-read sequencing. By comparing newly assembled genomes across different sampling time points, the tool will detect structural variation (deletion or insertions into the genome) in microbial genomes. Additionally, genomic inversions (“flipping” of the orientation of DNA) and genes associated with these changes will also be identified.