Divalent Cation Signaling in Spore Germination.

Spore germination plays an essential role in the pathogenesis of -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 . However, whether Ca or DPA alone can induce germination is unknown. Therefore, we aimed to evaluate the possible roles of Ca and other divalent cations present in the spore core, such as Mn and Mg, in spore germination. Our study demonstrated that (i) Ca-DPA, but not DPA alone, induced spore germination, suggesting that Ca might play a signaling role; (ii) all tested calcium salts induced spore germination, indicating that Ca is critical for germination; (iii) the spore-specific divalent cations Mn and Mg, but not Zn, induced spore germination, suggesting that spore core-specific divalent cations are involved in spore germination; and (iv) endogenous Ca and Mg are not required for induction of spore germination, whereas exogenous and partly endogenous Mn 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.