Abstract:
C. perfringens is a Gram-positive, spore-forming, anaerobic pathogenic
bacterium capable of causing a wide variety of diseases in both humans and animals.
However, the two most common illnesses in humans are C. perfringens type A food
poisoning (FP) and non-food-borne (NFB) gastrointestinal (GI) illnesses . These two
major diseases are caused only by C. perfringens Type A isolates that produce the C.
perfringens enterotoxin (CPE). Interestingly, C. perfringens isolates involved in FP
carry CPE-encoding gene (cpe) on the chromosome while isolates causing NFB GI
illnesses (i.e., sporadic diarrhea and antibiotic-associated diarrhea) carry a plasmid
borne copy of the cpe. C. perfringens is able to form highly resistance spores that can
survive in the environment for years. These spores are the infectious cell morphotype,
and in presence of favorable condition, they can germinate and return to active growth
to cause disease. Spore germination is an early and essential stage in the progression
of C. perfringens infection in humans and animals. The germination process can be
initiated by a variety of chemicals, including nutrients, cationic surfactants, and
enzymes termed germinant. Germination of Clostridium species has been less well
studied than Bacillus species. However, recent findings have identified the germinants
of spores of C. perfringens FP and NFB isolates.
Our overall goal was to characterize the germinant (ger) receptors of spores of
NFB isolates. Here through the construction of a gerAA knock out mutant we
characterized the role of GerAA in the germination of spores of C. perfringens NFB
isolate F4969. Result from these study indicate that in contrast to the minor role of
GerAA in germination of spores of C. perfringens FP isolates, GerAA has a major role
in spore germination of C. perfringens NFB isolates. Indeed, F4969 and SB103 spores
germinated less than wild-type spores with nutrient broth, the mixture L-Asn and KCl
(AK) and the non-nutrient germinant, dodecylamine. In addition, gerAA mutant spores
had lower rates of DPA release than wild-type spores in the presence of AK and
dodecylamine. These defects became evident in the slower outgrowth exhibited by
SB103 spores, but not on overall spore viability. Collectively, these results indicate, in
contrast to the role of GerAA in FP spores, that GerAA is a major germinant receptor
protein in NFB spores.
