Bile Acid Recognition by the Clostridium difficile Germinant Receptor, CspC, Is Important for Establishing Infection

Abstract

Clostridium difficile spores must germinate in vivo to become actively growing bacteria in order to produce the toxins that are necessary for disease. C. difficile spores germinate in vitro in response to certain bile acids and glycine. In other sporulating bacteria, proteins embedded within the inner membrane of the spore sense the presence of germinants and trigger the release of Ca++-dipicolinic acid (Ca++-DPA) from the spore core and subsequent hydrolysis of the spore cortex, a specialized peptidoglycan. Based upon homology searches of known germinant receptors from other spore-forming bacteria, C. difficile likely uses unique mechanisms to recognize germinants. Here, we identify the germination-specific protease, CspC, as the C. difficile bile acid germinant receptor and show that bile acid-mediated germination is important for establishing C. difficile disease in the hamster model of infection. These results highlight the importance of bile acids in triggering in vivo germination and provide the first description of a C. difficile spore germinant receptor. Blocking the interaction of bile acids with the C. difficile spore may represent an attractive target for novel therapeutics.

Clostridium difficile Infection: Pathogenesis, Diagnosis and Treatment

“…It is thought that CspC, a serine protease involved in germination in Clostridium perfringens, is a bile salt specific germinant receptor. It is known that CspC is required for Ca-DPA activation in spore germination in response to glycine and taurocholate [26].…”

Cross-talk between bile acids and intestinal microbiota in host metabolism and health

“…2d) (Sorg and Sonenshein, 2008;Heeg et al, 2012). The germination-specific protease CspC, which can recognize BAs, has a vital role in C. difficile germination and further C. difficile infection (Francis et al, 2013). However, secondary BAs such as LCAs and UDCAs can suppress C. difficile germination .…”

Detecting Cortex Fragments During Bacterial Spore Germination

“…Heat activate C. difficile spores at 65 °C for 30 min and store on ice. Note: C. difficile spores can be produced and purified as described previously 7,9,10 . 2.…”

“…In many spore-forming bacteria, these germinants are amino acids, sugars, nucleotides, ions or combinations thereof 2 . C. difficile spore germination is initiated by combinations of certain bile acids, [e.g., taurocholic acid (TA)] and amino acids (e.g., glycine) [7][8][9][10] . Though there are differences between the C. difficile germination pathway and the pathways studied in other spore-forming bacteria, such as B. subtilis, common to all is the absolute requirement to degrade the spore cortex to allow a vegetative cell to grow from the germinated spore 2,8 .…”