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|Title:||Superoxide Dismutase Activity During Thermal Stress and Recovery of Staphylococcus Aureus|
|Author(s):||Bucker, Edward Richard, Jr.|
|Department / Program:||Food Science|
|Degree Granting Institution:||University of Illinois at Urbana-Champaign|
|Abstract:||The superoxide dismutase (SOD) activity during growth, following injury and during the recovery of Staphylococcus aureus was examined. During the growth cycle of S. aureus MF-31, the SOD activity decreased during the lag phase, paralleled a concurrent increase in cell counts during the logarithmic phase and became constant in the stationary phase. The SOD activity during the stationary phase of S. aureus strains 196E and 210 was approximately 80% greater than for MF-31 whereas the SOD activities of strains S-6 and 181 were about 9 and 18% less, respectively. Anaerobically-grown cells of S. aureus MF-31 contained 41% less SOD activity than similar aerobically-grown cells.
A linear decrease in SOD activity occurred when cells of S. aureus MF-31 were thermally-stressed for 90 min at 52 C in 100 mM potassium phosphate buffer, pH 7.2. After 20 min of heating, approximately 5% of the SOD activity was lost whereas after 60, 90 and 120 min the SOD activity decreased by ca. 10, 22 and 68%, respectively. The rates of thermal inactivation of SOD from S. aureus strains 210 and 196E were similar and slightly greater than for strains MF-31, 181 and S-6. Heating of S. aureus cells at 62 C resulted in the rapid death of these cells which paralled a rapid thermal inactivation of SOD. The T(,50) for whole cells and cell lysates of S. aureus MF-31 was 57.5 and 51.7, respectively. The addition of NaCl prior to or after heating resulted in similar increased losses in SOD activity which were proportional to the amount of NaCl added. When cells of S. aureus were propagated in tryptic soy broth (TSB) or TSB containing up to 10% NaCl (TSBS), the SOD activities of the stationary phase cells was unchanged. Exposure of crude cell lysates of S. aureus MF-31 to 5 mM H(,2)O(,2) for 16 min resulted in a ca. 13% loss in SOD activity. These results suggested that the combined loss in SOD activity of thermally-stressed cells which resulted from exposure to heat, NaCl and H(,2)O(,2) may be one of the factors involved in the decreased enumeration of thermally-stressed cells on high salt-containing medium.
Thermally-stressed cells recovered in TSB exhibited an 85% decrease in the SOD activity following inoculation into the recovery medium. The SOD levels rapidly increased after the thermally-stressed cells repaired their heat-induced lesions and entered logarithmic growth. The SOD activity increased more rapidly and to a greater extent during the recovery of stressed cells than during the growth of nonstressed cells. When stressed cells were recovered in TSBS, a similar decrease in the SOD activity level occurred. However, a significant increase in SOD activity was not observed during the 12 hr recovery period examined. Additional evidence is presented which further supports the theory that the synergistic effects of heat and NaCl result in the decreased activity of catalase in the stressed cells, allowing the accumulation of toxic levels of H(,2)O(,2).
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1979.
|Date Available in IDEALS:||2014-12-13|
This item appears in the following Collection(s)
Dissertations and Theses - Food Science and Human Nutrition
Graduate Dissertations and Theses at Illinois
Graduate Theses and Dissertations at Illinois