Clostridium perfringens type A isolates carrying a chromosomal copy of the enterotoxin (cpe) gene are involved in the majority of food poisoning (FP) outbreaks, while type A isolates carrying a plasmid-borne cpe gene are involved in C. perfringens-associated non-food-borne (NFB) gastrointestinal diseases. To cause diseases, C. perfringens spores must germinate and return to active growth. Previously, we showed that only spores of FP isolates were able to germinate with K(+) ions. We now found that the spores of the majority of FP isolates, but none of the NFB isolates, germinated with the cogerminants Na(+) and inorganic phosphate (NaP(i)) at a pH of approximately 6.0. Spores of gerKA-KC and gerAA mutants germinated to a lesser extent and released less dipicolinic acid (DPA) than did wild-type spores with NaP(i). Although gerKB spores germinated to a similar extent as wild-type spores with NaP(i), their rate of germination was lower. Similarly, gerO and gerO gerQ mutant spores germinated slower and released less DPA than did wild-type spores with NaP(i). In contrast, gerQ spores germinated to a slightly lesser extent than wild-type spores but released all of their DPA during NaP(i) germination. In sum, this study identified NaP(i) as a novel nutrient germinant for spores of most FP isolates and provided evidence that proteins encoded by the gerKA-KC operon, gerAA, and gerO are required for NaP(i)-induced spore germination.