Clostridium perfringens spore germination:: Characterization of germinants and their receptors

Clostridium perfringens food poisoning is caused by type A isolates carrying a chromosomal enterotoxin (cpe) gene (C-epe), while C. perfringens-associated non-food-borne gastrointestinal (GI) diseases are caused by isolates carrying a plasmid-borne cpe gene (P-epe). C. perfringens spores are thought to be the important infectious cell morphotype, and after inoculation into a suitable host, these spores must germinate and return to active growth to cause GI disease. We have found differences in the germination of spores of C-epe and P-epe isolates in that (i) while a mixture Of L-asparagine and KCl was a good germinant for spores of C-epe and P-epe isolates, KCI and, to a lesser extent, L-asparagine triggered spore germination in C-epe isolates only; and (ii) L-alanine or L-valine induced significant germination of spores of P-epe but not C-epe isolates. Spores of a gerK mutant of a C-epe isolate in which two of the proteins of a spore nutrient germinant receptor were absent germinated slower than wild-type spores with KCI, did not germinate with L-asparagine, and germinated poorly compared to wild-type spores with the nonnutrient germinants dodecylamine and a 1:1 chelate of Ca2+ and dipicolinic acid. In contrast, spores of a gerAA mutant of a C-epe isolate that lacked another component of a nutrient germinant receptor germinated at the same rate as that of wild-type spores with high concentrations of KCI, although they germinated slightly slower with a lower KCI concentration, suggesting an auxiliary role for GerAA in C. perfringens spore germination. In sum, this study identified nutrient germinants for spores of both C-cpe and P-epe isolates of C. perfringens and provided evidence that proteins encoded by the gerK operon are required for both nutrient-induced and non-nutrient-induced spore germination.