Analysis of Peptidoglycan Structural Changes and Cortex Lytic Enzymes during Germination of Bacillus anthracis Spores
Dowd, Melissa Margaret
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Sporulation is a process of differentiation that allows capable cells to go into a dormant and resistant stage of life. To become active again, the spores must germinate into vegetative cells. One key process in spore germination is hydrolysis of the cortex peptidoglycan. This process has been studied in a variety of sporulating species; however, it has not been studied in Bacillus anthracis. A clear understanding of cortex degradation may provide information that will allow for better cleanup of spore contaminated sites. The structure of cortex peptidoglycan of Bacillus anthracis was characterized. The peptidoglycan of the dormant spores was extracted, digested with Mutanolysin, and analyzed using HPLC to determine the structure. The analyses revealed that the cortex peptidoglycan of B. anthracis was very similar to other Bacillus sp.. Spores were stimulated to germinate and cortex peptidoglycan was extracted and analyzed at various times. Bacillus anthracis appeared to hydrolyze its cortex more rapidly than other Bacillus species. While the spores of three species release the spore solute dipicolinic acid and resume metabolism at similar rates, the B. anthracis spores released 75% their cortex material within 10 minutes while the other species released only 20% in the same time frame. This suggests that the B. anthracis spore coats are more permeable to cortex fragments than those of the other species, or that B. anthracis rapidly cleaves the cortex into smaller fragments. Novel cortex fragments analyzed during B. anthracis germination were produced by a glucosaminidase; however, additional studies need to be performed for confirmation.
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