Divalent Cation Signaling in Clostridium perfringens Spore Germination

Spore germination plays an essential role in the pathogenesis of Clostridium perfringens-associated food poisoning. Germination is initiated when bacterial spores sense various stimuli, including chemicals and enzymes. A previous study showed that dipicolinic acid (DPA) chelated with calcium (Ca-DPA) significantly stimulated spore germination in C. perfringens. However, whether Ca(2+) or DPA alone can induce germination is unknown. Therefore, we aimed to evaluate the possible roles of Ca(2+) and other divalent cations present in the spore core, such as Mn(2+) and Mg(2+), in C. perfringens spore germination. Our study demonstrated that (i) Ca-DPA, but not DPA alone, induced C. perfringens spore germination, suggesting that Ca(2+) might play a signaling role; (ii) all tested calcium salts induced spore germination, indicating that Ca(2+) is critical for germination; (iii) the spore-specific divalent cations Mn(2+) and Mg(2+), but not Zn(2+), induced spore germination, suggesting that spore core-specific divalent cations are involved in C. perfringens spore germination; and (iv) endogenous Ca(2+) and Mg(2+) are not required for induction of C. perfringens spore germination, whereas exogenous and partly endogenous Mn(2+) are required. Collectively, our results suggest that exogenous spore core-specific divalent cation signals are more important than endogenous signals for the induction of spore germination.