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A role for bacterial urease in gut dysbiosis and Crohn’s disease

Bacterial urease activity of the gut microbiota alters nitrogen flux, leading to gut dysbiosis and worsening of colitis in mice. Nitrogen flux and gut dysbiosis Ni et al. used shotgun metagenomic and metabolomic analysis of fecal samples from pediatric patients with Crohn’s disease. They demonstrated an association between disease severity, gut dysbiosis, and free amino acids. A heavy isotope–labeled nitrogen flux analysis showed that bacterial urease activity led to the transfer of host-derived nitrogen to the gut microbiota, boosting amino acid synthesis. Inoculation of a murine host with Escherichia coli engineered to express urease led to dysbiosis associated with worsened immune-mediated colitis and increased amino acid production. A potential role for nitrogen flux in the development of gut dysbiosis suggests that urease may be a potential target for developing treatments for inflammatory bowel diseases. Gut dysbiosis during inflammatory bowel disease involves alterations in the gut microbiota associated with inflammation of the host gut. We used a combination of shotgun metagenomic sequencing and metabolomics to analyze fecal samples from pediatric patients with Crohn’s disease and found an association between disease severity, gut dysbiosis, and bacterial production of free amino acids. Nitrogen flux studies using 15N in mice showed that activity of bacterial urease, an enzyme that releases ammonia by hydrolysis of host urea, led to the transfer of murine host-derived nitrogen to the gut microbiota where it was used for amino acid synthesis. Inoculation of a conventional murine host (pretreated with antibiotics and polyethylene glycol) with commensal Escherichia coli engineered to express urease led to dysbiosis of the gut microbiota, resulting in a predominance of Proteobacteria species. This was associated with a worsening of immune-mediated colitis in these animals. A potential role for altered urease expression and nitrogen flux in the development of gut dysbiosis suggests that bacterial urease may be a potential therapeutic target for inflammatory bowel diseases.