The human gut is home to trillions of microbes that play a critical role in health and disease. My laboratory investigates common beneficial bacteria that colonize the intestinal mucus layer. While these bacteria offer benefits including improved metabolic health, they can also weaken the gut’s protective mucus barrier, leading to inflammation. We are using advanced genetic techniques to engineer probiotic strains that maximize health benefits, while maintaining gut safety. A major focus of our work is to engineer these bacteria as probiotics to promote healthy aging and longevity, and as innovative new types of vaccines. We are also working on strategies to modulate mucus degrading bacteria in the gut to combat graft-versus-host disease, a serious post-transplant condition. Using a combination of genetics, animal models, and bacteria isolated from human donors, we aim to contribute to the development of safe and effective microbiome-based therapeutics.