Researchers at the University of Notre Dame and collaborators have disclosed the core assembly of the germinosome, which is the alarm system that awakens the dormant spores of Clostridioides difficile (C. diff), a health threat that causes about half a million infections and about 30,000 deaths a year.
The study in Nature Communications was led at Notre Dame by Mayland Chang, research professor, and Shahriar Mobashery, Navari Family Professor in Life Sciences, both in the Department of Chemistry and Biochemistry, with collaboration from the National Spanish Research Council (CSIC). The research reveals a blueprint of the germinosome, which is the cellular machinery that senses when a dormant spore of the bacterium in the gut can become active by bile salts to initiate an infection.
C. diff spores exist in peoples’ intestines, and are held in check by healthy bacteria in peoples’ guts. People are more likely to experience a C. diff infection while taking an antibiotic, shortly after finishing an antibiotic regimen, or if they are immunocompromised.
The spores are triggered for conversion to the vegetative C. diff, the species that causes infections, by bile salts and amino acids, said Chang and Mobashery. The spores themselves are impervious to antibiotics. Once spores are germinated, the vegetative C. diff colonizes and inflames intestines, leading to severe diarrhea, which is the cause of significant morbidity and mortality.
Because standard medical treatment does not destroy the spores, many patients develop recurrent infections, Chang said, adding, “We've heard of patients who have years of recurrent C diff infections."
Chang and Mobashery used biophysical methods with purified recombinant proteins—lab engineered proteins created and purified for research— to reveal interactions between two germinosome proteins, taurocholate and glycine. X-ray crystallography and cryo-EM structural contributions were provided by the Hermoso lab at CSIC.
"It's a cascade of events. It's a highly intricate and very detailed process that has to take place precisely," said Mobashery. "In essence, there is a recognition between the proteins CspA and CspC, and this recognition between the two is highly potent. Once those two proteins are produced, they latch onto the taurocholate and the glycine. This is the process that initiates the germination event, Mobashery said.
There are multiple proteins in the germination process, Mobashery said, and if just one of the proteins can be blocked by a drug, then the spores can’t germinate and patients won’t develop disease.
“I think understanding the fundamentals of how spores germinate is going to be profoundly important," he said.
Chang and Mobashery, who are affiliated with the Eck Institute for Global Health, the Berthiaume Institute for Precision Health, and the Warren Center for Drug Discovery, plan to continue studying all the proteins in the C. diff germination cascade in their efforts to bring clarity to their biochemical functions.
“And then, more importantly, perhaps we will have elucidated the details of a wonder of nature,” Mobashery said.
The research at Notre Dame is supported by a grant from the National Institute of Allergy and Infectious Diseases in the U.S., the Chemistry-Biochemistry-Biology Interface Training Program supported by the National Institute of General Medical Science.
Originally published by at science.nd.edu on August 17, 2026.