Molecular analysis of GerP and spore-associated proteins of Bacillus cereus
Spores of various strains of Bacillus cereus are the causative agents of emetic and diarrheal foodborne illnesses. Typically, spores will survive thermal treatments that destroy vegetative cells, and then go on to germinate to form the vegetative cells that are associated with toxin production. The spore has to germinate in order to develop into the vegetative cells that produce toxins, hence a thorough understanding of the proteins and molecular mechanisms that underpin spore germination are of great significance from spore control perspectives. A major objective of this thesis was to use molecular genetic and fluorescence microscopy techniques to characterise the location and function of the GerP proteins in Bacillus cereus 14579. The GerP proteins have been identified from mutagenesis studies across the Bacilli as being implicated in spore germination, most likely by impacting upon the permeability of the spore coat. Data presented in this thesis reveal that the various GerP proteins all localise to the same inner-coat vicinity within the spore, as determined via the super-resolution ellipsoid localisation microscopy technique. The study also reveals that only the GerPA protein is required for the localisation of the other GerP proteins in the developing spore. A number of other coat and or germination associated proteins in B. cereus 14579 were examined in the course of this work. These include the GerN and GerT antiporters, which are both shown to have an involvement in inosine mediated spore germination in this strain. However, hypothetical interactions between antiporter proteins and the ‘linker-like’ N-terminal domain of the GerIA inosine-responsive germinant receptor protein appear unlikely since spores engineered with a truncated GerIA receptor subunit germinate normally. The protein encoded at locus BC1245 was also examined in this work, since it too had been implicated in spore germination. Data presented in this thesis indicate that this is not the case, and that the protein is a component of the spore coat. Overall, the work conducted in this project contributes to knowledge of spore assembly, spore structure and mechanisms that underpin germination, which ultimately, should permit the development of improved methodologies for spore control.
Bacillus cereus, spore germination, food poisoning, endospores
Networked Digital Library of Theses and Dissertations