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The bacterium Clostridium perfringens is a gram-positive anaerobe responsible for many diseases in man and other animals, the most common of which is acute food poisoning (AFP). It is estimated that nearly 240,000 cases of AFP occur each year in the U.S. The C. perfringens spore plays an important role in this infection. The heat resistance of the spore allows the organism to survive the cooking process, grow in the cooling food, and infect the victim. Despite the occurrence of this disease and the importance of the spore to this process, little work has been performed to determine how heat resistance is obtained and maintained by C. perfringens spores. In this work we study the spores and sporulation process of C. perfringens to determine what factors are most important in the formation of a heat resistant spore. We analyzed the spores produced by nine wild-type strains, including five heat-resistant food poisoning isolates and four less heat-resistant environmental isolates. We determined that threshold core density and a high ratio of cortex peptidoglycan relative to germ cell wall were necessary components of a highly heat-resistant spore. In order to test these observations, we constructed two mutant strains. The first could not achieve the necessary level of core dehydration and rapidly lysed in solution. The second mutant had a reduced amount of cortex relative to germ cell wall, and suffered a corresponding decrease in heat resistance as compared to our wild-type strains. The mutant strains supported the observations drawn from our wild-type strains. Dipicolinic acid is a major component of bacterial spores and is necessary for spore heat resistance. The Cluster I clostridia, including C. perfringens, lack the known DPA synthase operon, spoVF. We developed an in vitro assay for detecting DPA synthetase activity and purified the active enzyme from sporulating C. perfringens crude extract and identified the proteins with mass spectrometry. These results identified the electron transfer flavoprotein alpha chain (EtfA) as the DPA synthase of C. perfringens. Inactivating the etfA gene in C. perfringens resulted in a strain that could begin, but not complete, the sporulation process and produced dramatically lower amounts of DPA than the wild-type. The purified enzyme was shown to produce DPA in vitro and utilized FAD as a preferred cofactor. The results of this research may lead to future techniques to decrease the occurrence of the diseases caused by C. perfringens spores and treatments which may carry over to the diseases caused by similar organisms. / Ph. D.

Field research was undertaken in three Jamaican farming communities to understand the localized health impact of pesticide poisoning in a developing country. The primary research tool was the collection of data through an intra-household survey, complemented by field observations. The goal was to gather information on the extent to which pesticides are used, the physiological symptoms experienced during or after pesticide exposure, and the farmers' knowledge, attitude, and practice of safe pesticide use. Secondly, I examined the structural constraints to regulating pesticide usage and promoting safe practices, based on interviews with local health care providers and key officials in agriculture, health, and agro-business. The research proved that acute pesticide poisoning is widespread in Jamaica. Furthermore, health outcomes varied geographically particularly as related to the nature of the crop and pest problems. There was some effort within the agricultural and medical branch of the Jamaican government to address this concern; however, evidence that farmers had widely adopted safe application practices did not exist. I found that hazardous pesticide practices were not simply traced to farmers' ignorance. Rather, farmers showed substantial awareness of safety procedures but often chose not to practice them. The matter was further complicated by the general lack of knowledge among health care providers in identification and proper treatment of poisoning. / Master of Science

Call number: LD2668 .T4 1985 S72 / Master of Science

This item was digitized as part of the Million Books Project led by Carnegie Mellon University and supported by grants from the National Science Foundation (NSF). Cornell University coordinated the participation of land-grant and agricultural libraries in providing historical agricultural information for the digitization project; the University of Arizona Libraries, the College of Agriculture and Life Sciences, and the Office of Arid Lands Studies collaborated in the selection and provision of material for the digitization project.

Diss. (sammanfattning) Umeå : Univ., 2007. / Härtill 4 uppsatser.

Diss. (sammanfattning) Umeå : Univ., 2007. / Härtill 4 uppsatser.

Thesis (doctoral)--Munich, 1934. / Includes bibliographical references (p. 23-24).

Thesis (doctoral)--Munich, 1934. / Includes bibliographical references (p. 23-24).

Thesis (M. Sc.)--University of Hong Kong, 1997. / Includes bibliographical references (leaf i-ix).