Overview
Morganella morganii is a Gram-negative, facultatively anaerobic rod belonging to the family Morganellaceae (formerly classified within Enterobacteriaceae). It inhabits the human gastrointestinal tract as a low-abundance commensal but becomes an opportunistic pathogen in immunocompromised hosts, causing urinary tract infections, wound infections, and sepsis.
Metal Dependencies
M. morganii produces a potent nickel-dependent urease that hydrolyzes urea to ammonia, raising local pH. This pH shift increases the bioavailability of iron and zinc, creating a self-reinforcing niche. The organism also deploys siderophore systems for iron acquisition in competition with the host's nutritional immunity defenses.
Ecological Role
In a healthy gut, M. morganii remains at trace abundance, outcompeted by dominant commensals. During dysbiosis — particularly when iron availability rises or commensal diversity drops — it can expand rapidly. Its urease activity alkalinizes the local environment, potentially disrupting acid-tolerant beneficial taxa and favoring co-expansion of other Proteobacteria.
Conditions Associated
M. morganii is clinically significant in nosocomial infections and has been detected at elevated levels in gut microbiome profiles of patients with inflammatory bowel disease and post-surgical complications. Its intrinsic resistance to multiple antibiotics, including ampicillin and first-generation cephalosporins, complicates treatment.
Cross-References
- nickel — urease cofactor
- iron — siderophore competition
- urease — key virulence enzyme
- nutritional immunity — host metal sequestration