Clostridium perfringens spore germination plays a critical role in the pathogenesis of C. perfringensassociated
food poisoning (FP) and non-food-borne (NFB) gastrointestinal diseases. Germination is
initiated when bacterial spores sense specific nutrient germinants (such as amino acids) through germinant
receptors (GRs). In this study, we aimed to identify and characterize amino acid germinants for
spores of enterotoxigenic C. perfringens type A. The polar, uncharged amino acids at pH 6.0 efficiently
induced germination of C. perfringens spores; L-asparagine, L-cysteine, L-serine, and L-threonine triggered
germination of spores of most FP and NFB isolates; whereas, L-glutamine was a unique germinant for FP
spores. For cysteine- or glutamine-induced germination, gerKC spores (spores of a gerKC mutant derivative
of FP strain SM101) germinated to a significantly lower extent and released less DPA than wild type
spores; however, a less defective germination phenotype was observed in gerAA or gerKB spores. The
germination defects in gerKC spores were partially restored by complementing the gerKC mutant with a
recombinant plasmid carrying wild-type gerKA-KC, indicating that GerKC is an essential GR protein. The
gerKA, gerKC, and gerKB spores germinated significantly slower with L-serine and L-threonine than their
parental strain, suggesting the requirement for these GR proteins for normal germination of C. perfringens
spores. In summary, these results indicate that the polar, uncharged amino acids at pH 6.0 are effective
germinants for spores of C. perfringens type A and that GerKC is the main GR protein for germination of
spores of FP strain SM101 with L-cysteine, L-glutamine, and L-asparagine.