The study shows that good gut bacteria help the body make the antimicrobial peptide LL‑37 (called CRAMP in mice) via the HIF‑1α pathway, which blocks harmful Candida yeast from taking hold. Turning on HIF‑1α with drugs reduced yeast levels and death in mice, and antibiotics that kill gut microbes made the mice vulnerable. For biohackers, this suggests that keeping a healthy, anaerobic gut microbiome (e.g., with certain probiotics or fiber) and avoiding unnecessary antibiotics could boost natural antifungal defenses, and that compounds that activate HIF‑1α (like some dietary phytochemicals or vitamin D) might further enhance LL‑37 production.

Candida albicans colonization is required for invasive disease. Unlike humans, adult mice with mature intact gut microbiota are resistant to C. albicans gastrointestinal (GI) colonization, but the factors that promote C. albicans colonization resistance are unknown. Here we demonstrate that commensal anaerobic bacteria-specifically clostridial Firmicutes (clusters IV and XIVa) and Bacteroidetes-are critical for maintaining C. albicans colonization resistance in mice. Using Bacteroides thetaiotamicron as a model organism, we find that hypoxia-inducible factor-1α (HIF-1α), a transcription factor important for activating innate immune effectors, and the antimicrobial peptide LL-37 (CRAMP in mice) are key determinants of C. albicans colonization resistance. Although antibiotic treatment enables C. albicans colonization, pharmacologic activation of colonic Hif1a induces CRAMP expression and results in a significant reduction of C. albicans GI colonization and a 50% decrease in mortality from invasive disease. In the setting of antibiotics, Hif1a and Camp (which encodes CRAMP) are required for B. thetaiotamicron-induced protection against C. albicans colonization of the gut. Thus, modulating C. albicans GI colonization by activation of gut mucosal immune effectors may represent a novel therapeutic approach for preventing invasive fungal disease in humans.