Graduate Thesis Or Dissertation
 

Characterization of germinant receptors in Clostridium perfringens non-food-borne isolates

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  • 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.
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