MOLECULAR BIOLOGY OF GONOCOCCAL DEATH FOLLOWING EXPOSURE TO THE GRANULE EXTRACTS OF HUMAN NEUTROPHILS (NEISSERIA GONORRHOEAE, PEPTIDOGLYCAN, MEMBRANE DAMAGE).
AuthorROCK, JOHN PATRICK.
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PublisherThe University of Arizona.
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AbstractGonococci that have been phagocytized by human neutrophils are killed very effectively. While much research has focused on defining the microbicidal mechanisms of the neutrophil arsenal, substantially less is known regarding why phagocytized bacteria die. Gonococci were examined, at the molecular level, following exposure to human neutrophil granule extracts (GE) in an effort to discover the "lethal lesion", that injury to the bacterial cell which results in its death. The cytoplasm-based metabolism of GE-treated gonococci continues to function normally for at least 30 minutes, although these same cells have lost the ability to divide and are reproductively dead. GE-treated gonococci were found to utilize less oxygen than control cells, indicative of damage to the cytoplasmic membrane. Visual examination of GE-treated gonococci by light microscopy revealed that the cells undergo very minimal division once exposed to GE. GE-treated gonococci visualized by transmission electron microscopy had outer membranes which suffered time-related disorganization and disruption; the effects began immediately upon contact with GE. GE-treatment was also observed to cause aberrant structure and orientation of forming bacterial septa. Investigation of gonococcal peptidoglycan, the structural component of the bacterial membrane, yielded interesting results when the effects of GE were scrutinized. GE caused subnormal incorporation of peptidoglycan precursors, and also induced a twofold higher rate of release of peptidoglycan turnover fragments than was seen from control cells. After analysis of peptidoglycan fragments released into culture supernatants by thin-layer chromatography and high-pressure liquid chromatography, it was found that the small amount of high-molecular-weight fragments exhausted by control cells was not present with treated cells. Investigation of the cell-associated peptidoglycan, by the above methods, after exposure to GE revealed differences in the digestion products. There was a distinct reduction in the amount of penicillin bound by the penicillin-binding proteins of GE-treated cells. There was, however, no observed change in the electrophoretic mobility between the PBPs of control and treated cells.
Degree ProgramMolecular and Cellular Biology