Debaryomyces is enriched in Crohn’s disease intestinal tissue and impairs healing in mice

Fungal aggravation The gut microbiota includes not only prokaryotes, viruses, protists, and occasionally helminths, but also fungi. The role that fungi play in this symbiosis has long been overlooked. While investigating alterations to the gut microbiota in mice with mucosal damage and human subjects with Crohn's disease, Jain et al. discovered the fungus Debaryomyces hansenii localized to wounds in inflamed mucosal tissue (see the Perspective by Chiaro and Round). Impaired healing was associated with antibiotic treatment, overgrowth of the fungus, and subsequent induction of a type I interferon–CCL5 axis by macrophages. The fungus was observed within macrophages. Such persistent injury stimulus is a hallmark of inflammatory bowel diseases, including Crohn's disease and ulcerative colitis. It is not known whether this salt-tolerant fungus is a natural symbiont, but it is used in the food industry for surface ripening of cheese and meat products. Science , this issue p. 1154 ; see also p. 1102