Clostridium perfringens Spore Germination: Characterization of Germinants and Their Receptors

Abstract

ABSTRACT Clostridium perfringens food poisoning is caused by type A isolates carrying a chromosomal enterotoxin ( cpe ) gene (C- cpe ), while C. perfringens -associated non-food-borne gastrointestinal (GI) diseases are caused by isolates carrying a plasmid-borne cpe gene (P- cpe ). 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- cpe and P- cpe isolates in that (i) while a mixture of l -asparagine and KCl was a good germinant for spores of C- cpe and P- cpe isolates, KCl and, to a lesser extent, l -asparagine triggered spore germination in C- cpe isolates only; and (ii) l -alanine or l -valine induced significant germination of spores of P- cpe but not C- cpe isolates. Spores of a gerK mutant of a C- cpe isolate in which two of the proteins of a spore nutrient germinant receptor were absent germinated slower than wild-type spores with KCl, 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 Ca 2+ and dipicolinic acid. In contrast, spores of a gerAA mutant of a C- cpe 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 KCl, although they germinated slightly slower with a lower KCl 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- cpe 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.