Title page for ETD etd-05072008-115555


Type of Document Master's Thesis
Author Harry, Kathryn Helene
Author's Email Address kmullall@vt.edu
URN etd-05072008-115555
Title Sporulation and enterotoxin regulation by sigma factors in Clostridium perfringens
Degree Master of Science
Department Biology
Advisory Committee
Advisor Name Title
Melville, Stephen B. Committee Chair
Chen, Jiann-Shin Committee Member
Schubot, Florian D. Committee Member
Yang, Zhaomin Committee Member
Keywords
  • Clostridium perfringens
  • sporulation
  • sigma factors
  • CPE
  • food poisoning
Date of Defense 2008-04-28
Availability restricted
Abstract
Clostridium perfringens is a leading cause of food poisoning annually in the United States. Ingested C. perfringens vegetative cells respond to the acidic conditions of the stomach by initiating sporulation. The process of sporulation is essential in the formation of an enterotoxin (CPE) that is responsible for the symptoms of acute food poisoning. During sporulation, the cell must differentiate into the mother cell and the forespore. Studies in Bacillus subtilis have shown that gene expression during sporulation is compartmentalized, with different genes expressed in the mother cell and the forespore. The cell-specific RNA polymerase sigma factors coordinate the development of the differentiating cell. These sigma factors are σF, σE, σG, and σK. The C. perfringens cpe gene, encoding the enterotoxin CPE, is transcribed from three promoters, P1, P2, and P3. P2 and P3 were previously proposed to be σE-dependent, and P1 was proposed to be σK-dependent based on consensus recognition sequences. In this study, mutations were introduced into the sigE and sigK genes of C. perfringens. In the sigE and sigK mutants, promoter fusion assays indicated that there was no transcription of cpe in either mutant. We also determined through transcriptional analyses that σE-associated RNA polymerase and σK-associated RNA polymerase co-regulate the transcription of each other. RT-PCR analyses indicated that σK is a very early acting sigma factor. The evidence provided here shows that the regulation of sporulation in C. perfringens is not the same as it is in B. subtilis, as previously proposed.

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